© 2015 American Psychological Association 0882-7974/15/$ 12.00 http://dx.doi.org/10.1037/a0038973
Psychology and Aging 2015, Vol. 30, No. 2, 420-431
Daily Stressors and Emotional Reactivity in Individuals With Mild Cognitive Impairment and Cognitively Healthy Controls Elizabeth Hahn Rickenbach
Kristen L. Condeelis
Saint Anselm College
University of Alabama
William E. Haley University of South Florida Daily experiences of stress are common and have been associated with worse affect among older adults. People with mild cognitive impairment (PWMCI) have measurable memory deficits in between normal cognition and dementia and have been identified as having greater psychological distress than cognitively healthy older adults (CHOAs). Little is known about whether daily stressors contribute to distress among PWMCI. We hypothesized that compared with CHOAs, PWMCI would have higher daily negative affect and lower daily positive affect, report greater numbers and severity of daily stressors, and experience greater emotional reactivity to daily stressors. Fifteen clinically diagnosed PWMCI and 25 CHOAs completed daily reports of stressors, stressor severity, and positive and negative affect over an 8-day period. PWMCI reported higher daily negative affect, lower daily positive affect, and higher numbers and greater severity of memory stressors but did not differ from CHOAs in numbers or severity of general stressors. Cognitive status was a moderator of the daily stress-affect relationship. Days with greater numbers and severity of general daily stressors were associated with higher negative affect only for PWMCI. The numbers and severity of memory stressors were not associated with negative affect. In addition, more severe general daily stressors and memory stressors were associated with lower positive affect for all participants. Results suggest that PWMCI are less resilient in the face of daily stress than are CHOAs in terms of negative affect, perhaps because of declines in reserve capacity. The study presents a promising approach to understanding stress and coping in predementia states of cognition. Keywords: mild cognitive impairment, daily stress, daily affect
daily mood or emotional reactivity (DeLongis, Folkman, & Lazarus, 1988; Mroczek & Almeida, 2004). In addition, certain individuals may be more likely to experience greater stressorrelated increases in negative mood (i.e., greater emotional reactiv ity; Almeida, 2005). Past work suggests that individuals who are high in vulnerability to stress—for example, those high in neuroticism— may be more reactive to daily stress (Mroczek & Almeida, 2004). Mild cognitive impairment (MCI) is a diagnosis that has been developed with detailed diagnostic criteria (Petersen, 2004) and increasingly used in research and clinical settings such as memorydisorders clinics. In the latest edition of the American Psychiatric Association’s (2013) Diagnostic and Statistical Manual o f Mental Disorders (5th ed.), the diagnosis of mild neurocognitive disorder has been introduced. Mild neurocognitive disorder includes a broader spectrum of patients and does not currently have detailed published research diagnostic criteria, so the term MCI is more precise. People with MCI (PWMCI) have cognitive deficits that are not severe enough to merit a diagnosis of dementia, but they may be at risk for progression to dementia. By definition, PWMCI function fairly well, as evidenced by relatively intact activities of daily living (e.g., bathing, dressing themselves) and previous work stating that subtle differences in functioning may be difficult even for clinicians to ascertain (Petersen, 2004). However, PWMCI may be of particular interest as a group, because they may have differ-
There is extensive evidence that people who experience greater stress may be at risk for both worse psychological well-being and worse mental health (e.g., Lupien, McEwen, Gunnar, & Heim, 2009; Williams, Yan, Jackson, & Anderson, 1997). Stress may also be associated with momentary or short-term fluctuations in mood that occur within people over time (Bolger, Delongis, Kes sler, & Schilling, 1989). Thus, researchers interested in the role of stress in psychological aging have increasingly moved beyond using only global, retrospective reports of stress and well-being to also incorporate diary study designs, which provide benefits such as reducing recall bias and allowing for the examination of natu rally occurring fluctuations in a construct within people over time (Bolger, Davis, & Rafaeli, 2003). This research indicates that when people report greater daily stress, they also experience worse
This article was published Online First May 4, 2015. Elizabeth Hahn Rickenbach, Department of Psychology, Saint Anselm College; Kristen L. Condeelis, Department of Psychology, University of Alabama; William E. Haley, School of Aging Studies, University of South Florida. We thank Ross Andel, Amanda Smith, and Brent Small for providing their expertise and advice for this research project. Correspondence concerning this article should be addressed to Elizabeth Hahn Rickenbach, 100 Saint Anselm Drive, Box 1785, Manchester, NH 03102. E-mail: [email protected]
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DAILY STRESS IN MILD COGNITIVE IMPAIRMENT
ent experiences of stressors in daily life (e.g., difficulty managing a household or finances, interpersonal tension) than do cognitively healthy older adults (CHOAs) because of potential increased vul nerability. MCI is most commonly associated with deficits in memory and can be reliably assessed using neuropsychological assessments and clinical criteria (Albert et al., 2011; Petersen, 2004). PWMCI are at increased risk for development of Alzheimer’s disease (AD) compared with CHOAs. Conversion estimates, within a 5-year period, range from 26% to 50% of PWMCI, depending on the subtype of MCI (Fischer et al, 2007; Hanninen, Hallikainen, Tuomainen, Vanhanen, & Soininen, 2002). Although 11% of the population over the age of 65 is estimated to have Alzheimer’s disease (Alzheimer s Association, 2013), the prevalence of MCI, which varies widely by definition and study sample, is estimated to be between 22% and 71% (Ward, Arrighi, Michels, & Cedarbaum, 2012). By definition, PWMCI have memory impairment beyond that of CHOAs, but it does not reach the level of severity found in AD and does not significantly impair functioning or ability to perform daily activities (Albert et al., 2011). Research on well being among PWMCI has found that they have higher levels of depression and lower well-being than do CHOAs, but psycholog ical distress in MCI has often been conceptualized as a neuropsy chiatric symptom rather than within a more psychological frame work (e.g., Lyketsos et al., 2002). Moreover, the research has not considered daily affect; instead, most research has examined more stable experiences of well-being. The limited research to date on stress in MCI suggests that PWMCI experience frustration in their daily lives, difficulties in completing complex activities, and in terpersonal difficulties with family members that are focused on whether family members allow them to complete activities inde pendently, assist them with activities, or take control over certain complex activities (Blieszner, Roberto, Wilcox, Barham, & Win ston, 2007; Joosten-Weyn Banningh, Vemooij-Dassen, Olde Rikkert, & Teunisse, 2008; Mcllvane, Popa, Robinson, Houseweart, & Haley, 2008). Therefore, on the basis of past work (e.g., Blieszner et al., 2007), we hypothesized that greater memory difficulties associated with MCI may be associated with more daily stressors. Specifically, PWMCI and their spouses may report interpersonal tensions or the inability of the PWMCI to independently complete tasks of daily life, potentially resulting in home- or work-related stressors. There are a number of theoretical perspectives that could be useful in understanding daily stress and coping in PWMCI. For instance, PWMCI might experience more frequent daily stressors, including both general stressors and memory-related stressors, than do CHOAs because of their mild memory difficulties (i.e., reduced performance on neuropsychological tests). In addition, from a stress and coping perspective (Lazarus & Folkman, 1984), PWMCI might also appraise stressors as more stressful or severe if their coping resources are reduced because of diminished reserve capacity (Staudinger, Marsiske, & Baltes, 1993). Reserve capacity is a life-span developmental construct related to the idea that amid age-related declines, individuals have the capacity to cope with and adapt to losses. Certain factors, whether internal (e.g., cogni tive abilities) or external (e.g., support networks), contribute to reserve capacity (Staudinger, Marsiske, & Baltes, 1995), Thus, in the current study, we applied this theoretical framework to the investigation of whether individuals with reduced internal reserve
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capacity (i.e., those with MCI) are less able to avoid and cope with stressors in daily life. In other words, we hypothesized that with diminished resources (i.e., cognitive deficits associated with MCI), functioning will break down under high demand, leading to greater stressors and inability to cope with stressors. The strength and vulnerability integration model might also help to explain how older adults with MCI may be more likely to experience daily stressors and emotional distress than are CHOAs (Charles, 2010). This model posits that older adults reduce nega tive experiences and emotions in their daily lives in comparison with younger adults as a result of the effective use of strategies and behaviors. The cognitive deficits associated with MCI may disrupt effective strategy use, thus attenuating age-related benefits in emotional regulation. In line with these theoretical frameworks, PWMCI may expe rience greater fluctuations in daily affect when stressors occur, because evidence suggests that greater perceived stressor severity is associated with having fewer psychological resources. It is important to understand how PWMCI experience daily stressors and appraise them in comparison with CHOAs and to better recognize whether daily stressors are mechanisms through which PWMCI might experience poorer affect. We have not identified any studies that have used a short-term repeated measures design to examine intraindividual variation in naturally occurring experi ences of daily stress and affect in PWMCI and CHOAs. In com parison with retrospective measures, such methods have proven useful in providing a finer grained analysis of the experience of daily stress and memory problems in daily life. The current study used a novel approach to better understand daily stress processes and daily affect in PWMCI. Thus, it serves as a first step toward additional inquiry and understanding of the daily lives of individuals with MCI. Using a daily diary study design, we examined positive and negative affect, numbers of daily stressors (both general and memory specific), and perceived stressor severity in a sample of clinician-diagnosed PWMCI and CHOAs. To clarify, memory-specific daily stressors are instances such as forgetting the name of a friend or relative or forgetting the reason one entered a room, which are distinct from the memory deficits associated with MCI classification as operationalized by performance on neuropsychological tests. Both groups of partici pants included only individuals above a threshold on a measure of global cognitive status to ensure ability to complete daily diary measures. Covariates included demographic and health variables that might be related to daily stressors and affect. We initially examined daily experiences of affect, stressors, and stressor sever ity descriptively. First, on the basis of previous findings, we hypothesized that PWMCI would report higher average daily negative affect and lower average positive affect compared than would CHOAs. Second, we predicted that, on average, PWMCI would report more frequent memory problems than would CHOAs, but we did not predict whether the number of general daily stressors would differ between PWMCI and CHOAs. We also anticipated that, on average, PWMCI would appraise their general daily stressors and memory problems as more severe than would CHOAs because of their slightly reduced cognitive reserve capacity. Third, we examined emotional reactivity to both the numbers and the severity of daily stressors (general stressors and memory problems) and whether PWMCI and CHOAs differed in emotional reactivity. We defined emotional reactivity as worse
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affect (higher negative affect, lower positive affect) in response to daily stressors.
Method Sample and Recruitment The study included 15 PWMCI and 25 CHOAs recruited from the Alzheimer’s Disease Research Center (ADRC) at the Byrd Alzheimer’s Institute (Tampa, Florida). All study participants met the following inclusion criteria: (a) willing to complete a 1-hr baseline interview or mail-in questionnaire, (b) willing to complete eight consecutive days of 10-min phone interviews, (c) willing and able to give written informed consent, and (d) having scored at least 25 on a Mini-Mental State Examination (MMSE; Folstein, Folstein, & McHugh, 1975) or an equivalent score of 20 on the Telephone Interview for Cognitive Status (Brandt, Spencer, & Folstein, 1988). This latter criterion was included to comply with internal review board (IRB) procedures, to help ensure cognitive ability to provide informed consent, and to eliminate participants who might have developed dementia since their previous cognitive evaluations. Detailed descriptions of the MMSE and TICS are provided in the Baseline Interview Measures section. Participants with MCI met the following criteria: (a) seen by clinicians at the Byrd Alzheimer’s Center within the past year (ADRC assessments are conducted annually) and (b) given an MCI diagnosis at the previous visit, as determined by the ADRC diagnostic process. Participants who were cognitively healthy were required to meet those criteria and to have completed a neuropsychiatric evaluation at the Byrd Alzheimer’s Center to determine normal cognitive functioning within the past year. For all study participants, exclu sion criteria included the inability to speak and write in English. Compensation included the opportunity to win one of two $25 gift cards by lottery. The ADRC database includes individuals who have received extensive medical and neuropsychological evaluations. The data base includes approximately 110 CHOAs and 60 PWMCI. Of these, 99 who were identified by Byrd Institute staff as either having MCI or being controls and who participated in extensive neuropsychological testing during the current or previous year of the study were considered eligible for recruitment. Of those, a total of 60 (n = 34 [CHOA], n = 26 [PWMCI]) individuals agreed to be contacted by the current study’s research personnel, and, sub sequently, 40 agreed to participation and completed the study protocol (n = 25 [CHOA], n = 15 [PWMCI]). For the current study, the ADRC participants were asked if they were interested in participating in a “study on daily experiences of stress, health and aging.” Participants were told that “the purpose of this study is to find out how older adults deal with stress in their daily lives. We are also interested in understanding how hassles, bothersome events, or everyday problems with memory that occur in normal aging may make some people have worse mood.” As part of the current study and IRB-approved protocol, the classification as MCI or cognitively healthy participant willing to participate in the current study was provided to our research personnel. Results from chi-square analyses suggest that there were no significant differ ences between the two groups in their agreement to enroll in the study (p = .271). All study protocols were approved by the IRB at the University of South Florida.
Study Design Participants completed the informed consent and baseline inter view in person, when possible, and by mail if they lived more than an hour away. Within 2 weeks following the baseline interview, participants completed up to eight consecutive days of 10-min telephone interviews following a daily diary study design. Diary studies use self-reported measurements that participants complete multiple times over a short period of time, such as multiple times within a day, every day, or multiple times per week (Bolger et al., 1989). Events and experiences that meaningfully vary over a short period of time are intended for use in diary designs, because in these cases, there is variability to be measured and explained via daily reports (Affleck, Zautra, Tennen, & Armeli, 1999; Bolger et al., 2003). Participants completed daily interviews at a time con venient for them. Participants with MCI completed between four and five daily interviews (M = 4.67, SD = 2.53), and control participants completed between five and six daily interviews (M = 5.60, SD = 1.38). Independent samples t tests revealed no signif icant differences between the average number of interviews com pleted in MCI versus control participants {p = .127). The daily interviews lasted, on average, 7.29 min (SD = 1.83). PWMCI (M = 6.94 min, SD = 1.67) and CHOAs (M = 7.45 min, SD = 1.91) were not significantly different in the length of daily inter views (p = .437).
Determination of MCI A more detailed description of the criteria for MCI and the consensus conference for determination of MCI at the ADRC has been provided elsewhere (Duara et al., 2010; Schinka et al., 2010). In the ADRC study, participants and informants were interviewed for their clinical history. Participants also underwent clinical and neuropsychological evaluation, which included tests as part of the Uniform Data Set. As described in greater detail by previous publications (Morris et al., 2006; Weintraub et al., 2009), the Uniform Data Set includes tests of dementia severity (MMSE), attention (digit span forward and backward), processing speed (digit symbol), executive functioning (trail-making test), memory (e.g., immediate and delayed word recall), and language (category fluency, Boston Naming Test). MCI was determined through con sensus conference with trained geriatricians, neuropsychologists, and neurologists and followed previous research defining MCI as a state between normal cognitive aging and dementia (Petersen et al., 1999, 2003). Participants with MCI were identified as scoring 1.5 standard deviations below the mean on at least one cognitive domain for their age and education levels. Following Petersen’s (2004) criteria, they also met MCI criteria only if they showed no significant deficits in functional activities (e.g., bathing, dressing oneself). Participants were informed of their MCI diagnosis by clinicians as part of the ADRC study and were further classified as amnestic (memory domain affected) or nonamnestic (memory domain not affected) and single domain (only one domain af fected) or multiple domain (more than one domain affected). For the purposes of the current study and because of the small number of recently tested participants within each of the subtypes of MCI, the MCI subtypes were considered together as one group of MCI participants.
DAILY STRESS IN MILD COGNITIVE IMPAIRMENT
Baseline Interview Measures Basic demographic information. During the baseline inter view, demographic information, social factors, and health in formation were assessed. Demographic information included age, gender, education (highest level completed), race/ethnicity, and marital status. Additional information pertaining to social factors—such as current living arrangement, number of chil dren. and frequency with which the participant saw his or her children—was also assessed. During the baseline interview, participants were asked if a doctor had ever told them if they had any of five medical conditions (high blood pressure, cancer, heart problems, diabetes, and arthritis), and this information was used to create a sum score for the total number of health problems (range: 0-5). Global cognitive status. The MMSE (Folstein et al., 1975) was conducted during in-person baseline interviews. The MMSE covers multiple cognitive domains, and scores range from 0 to 30, with 30 being the best possible score. A widely used cutoff score of 25 (Borson, Scanlan, Chen, & Ganguli, 2003; Kim & Caine, 2002) served as a screening criterion to help ensure consenting capacity and was scored as in previous research (Fillenbaum, Hughes. Heyman, George, & Blazer, 1988). When the MMSE was not available from records or an in-person baseline interview was not conducted, participants completed the Telephone Interview of Cognitive Status (TICS; Welsh, Breitner, & Magruderhabib, 1993). The TICS-30 is an 11-item survey with scores ranging from 0 to 30, with higher scores indicating worse cognitive perfor mance. The TICS-30, which has been adapted from the TICS in previous research (Langa et al., 2005), is a global cognitive status instrument that has been found to be highly correlated with the MMSE (Desmond, Tatemichi, & Hanzawa, 1994). In the current study, a score of 20 on the TICS-30 was used as a cutoff as it has been determined to be equivalent to an MMSE score of 25 (Fong et al., 2009). For purposes of analyses, the TICS-30 scores were converted to MMSE scores on the basis of previous research (Fong et al., 2009). The TICS-30 and MMSE scores were not adjusted for education.
Daily Diary Measures Daily affect. Daily affect was assessed using a 12-item ver sion of the Positive and Negative Affect Schedule (PANAS; Wat son, Clark, & Tellegen, 1988), which includes six positive affect (PA) items (“cheerful,” “in good spirits,” “extremely happy,” “calm and peaceful,” “satisfied,” and “full of life”) and six nega tive affect (NA) items (“so sad nothing could cheer you up,” “nervous,” “restless or fidgety,” “worthless,” “hopeless,” and “that everything was an effort”). As part of the PANAS, participants were asked to report how much of the time during the past 24 hr they felt each of the items on a five-point scale: 0 (none of the time), 1 (a little of the time), 2 (some o f the time), 3 (most o f the time), or 4 (all o f the time). Scores were averaged for each scale, PA and NA, with higher scores indicating higher PA or NA (range: 0-4). Daily stressors. Participants were asked to report (yes/no) whether they had experienced any of 12 negative events within the past 24 hr. a scale adapted from previous research (Bolger et al., 1989; Cohen et al., 2008). Initially, participants were asked an open-ended question such as this: “Did anything particularly
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stressful happen during the past 24 hours?” Specific daily stressor questions followed the open-ended question and included inquiries concerning stress related to work, family demands, family mem bers being sick or injured, transportation, finances, spousal con flict, being ignored by a spouse, conflict with other family mem bers or friends, and avoiding activities because of health. The scale also incorporated two additional stressor questions: “Did someone do too much to help you with something?” and “Did someone not do enough to help you with something?” On the basis of past work (Blieszner et al., 2007; Joosten-Weyn Banningh et al., 2008), need for and receipt of support were hypothesized to be potentially relevant in a memory-impaired population. Consistent with previ ous daily diary research (Sliwinski, Almeida, Smyth, & Stawski, 2009), scores for total number of stressors (0-13) were summed for each day. To avoid repetition in counting events, the initial open-ended question was only included in the measure for total number of daily stressors if it was not included as a specific daily stressor in the follow-up questions. If the participant answered “yes” to experiencing a daily stres sor, he or she was then asked how severe the stressor was (i.e., how “stressful” the event was), with the following options: 0 {not at all), 1 {only a little), or 2 {a great deal). Participants who reported no stressor had a score of zero for stressor severity, and scores for the severity of events were summed for each day. Daily memory problems. Participants were asked seven questions pertaining to daily memory problems, a shortened ver sion of a 35-item measure (Sunderland, Harris, & Baddeley, 1983) adapted for daily format. The shortened format was similar to measures used in previous daily diary research in older adult populations (Neupert, Almeida, Mroczek, & Spiro. 2006). The seven questions, taken from the full questionnaire (Sunderland et al., 1983), were as follows: (a) “In the past 24 hours, did you go back to check whether you had done something that you meant to do?” (b) “In the past 24 hours, did you find that a word was ‘on the tip of your tongue,’ you knew what it was but could not quite find it?” (c) “In the past 24 hours, did you forget the names of friends or relatives or call them by the wrong names?” (d) “In the past 24 hours, did you forget something you had just said—maybe say, ‘What was I talking about?”’ (e) “In the past 24 hours, while reading, did you forget what the sentence is you have just read and have to reread it?” (f) “In the past 24 hours, did you forget where you had put something or lose something around the house?” (g) “In the past 24 hours, did you start to do something, then forget what it was you wanted to do—maybe saying, ‘What am I do ing?”’ Scores for memory problems were summed for each day and ranged from 0 to 7. Items were chosen on the basis of consultation with researchers with extensive experience in MCI, consensus, face validity, and examination of previously collected pilot data. If a participant answered “yes” to experiencing a memory prob lem, he or she was also asked a follow-up question to assess severity: “How stressful was that for you?” Similar to stressor severity, answer choices were 0 {not at all), 1 {only a little), or 2 {a great deal). Participants who reported no memory problems had a score of zero for stressor severity, and scores for the severity of events were summed for each day. The severity of memory prob lems was summed for each day.
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Statistical Approach For the first and second research aims, we compared daily affect, daily stressors, and daily stressor severity between PWMCI and CHOAs using independent samples t tests and chi-square analyses. For the third research aim, a series of multilevel models (MLMs) was conducted using PROC MIXED in SAS Version 9.2 to examine whether number and severity of stressors were predic tors of daily affect. MLMs have some specific advantages, includ ing the ability to handle missing data and to estimate variability within and between individuals (Affleck et al., 1999) by taking into account data that are hierarchical in nature, such as repeated measures within a person. MLM analyses included both Level-2 and Level-1 predictors of daily affect. Level-2 predictors included demographic factors (e.g., age, sex) in addition to the person mean or average of the daily diary data across up to 7 days. Level-1 predictors were nonaggregated data from each day of diary data. Level-1 predictors examined whether individuals had worse affect on days with greater daily stress, and Level-2 predictors examined whether individuals with greater stress, in general, had worse daily affect. In the within-person analyses, the total number of daily stressors and daily stressor severity were person-mean centered to examine the daily stressor in relation to a person’s average stress. The Level-2 predictors included the person mean for both the number and the severity of daily stressors across the eight daily diaries. Model specifications for all multilevel analyses included maximum likelihood estimation and an autoregressive covariance matrix to account for the dependency of data measured on days closer to each other versus farther apart. Also, intercept and time were considered random effects. Time was not included as a predictor in any of the analyses because it was not significantly correlated with any of the outcome measures and was not a variable of conceptual interest in the study. Predictors at Level 1 (e.g., number of stressors on a given day) and Level-2 person means (average number of daily stressors across up to 7 days) were both included, in line with past research, to better disaggregate the within-person and between-persons effects (Hoffman & Stawski, 2009). We conducted MLMs to examine (a) whether the number of daily stressors was associated with higher NA. (b) whether daily stressor severity was associated with higher NA, (c) whether the
number of memory problems was associated with higher NA. and (d) whether severity of memory problems was associated with higher NA. To estimate the moderating effect of MCI in the relationship between daily stressors and affect, we then added the interaction term of MCI and daily stressor number/severity. We then ran the same MLM, with PA as the outcome. Intraclass correlation coefficients were calculated to determine the variance in the Level-1 variables that was between persons (BP) and within person (WP). Unconditional models determined the following: general daily stressors (18% BP, 82% WP), memory stressors (58% BP, 42% WP), general stressor severity (9% BP, 91% WP), memory stressor severity (50% BP, 50% WP) PA (74% BP, 26% WP), and NA (82% BP, 18% WP). Power analyses were conducted for the sample size (N = 40) with two groups (15 MCI participants and 25 control participants) for Hypotheses 1 and 2; these included either daily estimates or baseline retrospective data. Post hoc power analyses estimated a power of .71 with a sample of 40 participants, a medium effect size (0.36), and a p value of .05. Because the current study also estimated regression coefficients using MLMs, primarily at Level 1 (daily stressors and daily memory problems) but also at Level 2, an effective sample size that considers the nature of hierarchical data was calculated on the basis of previous research (Savla, Roberto, Blieszner, Cox, & Gwazdauskas, 2011). For these anal yses, we used the 207 total days of analyses and an intraclass correlation coefficient of .60 to calculate an approximate effective sample size of 45 Level-2 units, consistent with previous research (Snijders, 2005), which yielded a statistical power of .74
Results On average, participants were 74 years old; 75% were White, and most were female, married, and had achieved more than a high school education (see Table 1). Most participants reported living with their spouse. Almost all had children, and half reported seeing their children weekly or daily. Participants reported, on average, two out of five health problems. MCI participants were signifi cantly more likely than controls to have more total health problems and to score lower on the MMSE. The two groups did not differ significantly on the other descriptive variables. The intercorrela-
Table 1 Descriptive Characteristics For Study Participants Variable
All (N = 40)
PWMCI (n = 15)
CHOAs (n = 25)
P
Age in years (M ± SD) Female (%) Education (% more than high school) Race (% White) Married (%) Living alone (%) Have children (%) See children regularly (% weekly or daily) Total number of health problems (M ± SD) MMSE score0 (M ± SD)
74.22 ± 6.45 75 80 75 65 30 95 50 1.99 ± 1.01 27.93 ± 1.53
75.33 ± 5.34 60 80 73.3 80 20 100 46.7 2.24 ± 1 .1 9 26.93 ± 1.44
73.56 ± 7.05 84 80 76 56 36 92 52 1.88 ± 0.89 28.52 ± 1.26
.407 .09 1 .85 .123 .274 .261 .202 .03 .001
Note. PWMCI = people with mild cognitive impairment; CHOAs = cognitive healthy older adults; MMSE = Mini-Mental State Examination. a For 12 participants, the Telephone Interview for Cognitive Status (TICS) was administered over the phone rather than MMSE, and TICS scores were converted to MMSE scores according to previous research (Fong et al., 2009).
DAILY STRESS IN MILD COGNITIVE IMPAIRMENT
tions for all study variables are displayed in Table 2, separately for PWMCI and CHOAs.
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interaction effect is illustrated in Figure 2 and suggests that on days when a person with MCI reported greater stressor severity than usual, he or she had significantly higher NA than did a control participant on a day when he or she reported greater stressor severity than usual. The interaction between the person mean of stressor severity and MCI was also significant, suggesting that greater stressor severity, on average, was associated with higher NA among PWMCI in particular. In analyses predicting PA, being married was predictive of higher PA and was included as a covariate. The number of health problems was also included as a covariate because of group differences between MCI and CHOA participants. The results for daily stressor numbers and severity in relation to PA are displayed in Table 4. The number of daily stressors was not related to PA, and there were no moderating effects of MCI. However, the person mean of the severity of stressors was related to PA, suggesting that participants who reported more severe stressors, on average, re ported lower PA. There was no moderating effect of the interaction of stressor severity and MCI predicting PA. Memory stressors. In analyses predicting NA, younger age was predictive of higher NA and was included as a covariate. The number of health problems was also included as a covariate because of group differences between MCI and CHOA partici pants. There was no main effect of the number of memory stressors in relation to NA; however, the interaction effect of PM memory stressors and MCI predicting NA was significant (see Table 5). This interaction effect is graphed in Figure 3 and suggests that reporting more daily stressors, on average, was associated with greater NA, especially among PWMCI. Memory stressor severity was not associated with NA, and there were no moderating effects of cognitive status. In analyses predicting PA, being married was predictive of higher PA and was included as a covariate. The number of health problems was also included as a covariate because of group differences between MCI and CHOA participants. When we ex amined daily memory problems predicting daily PA, results showed that greater numbers of memory problems (person means) were associated with lower PA (see Table 5). There was no significant interaction effect with MCI, suggesting that regardless
Daily Affect, Daily Stressors, and Stressor Severity Our first and second research aims examined daily affect, daily stressors, and severity of stressors for PWMCI and CHOAs. For the daily measures of affect, participants with MCI reported sig nificantly lower daily PA and significantly higher daily NA (see Table 3). Participants reported, on average, between one and two stressors each day, and they reported at least one stressor on approximately 74% of days. Participants reported between one and two memory problems per day, and they reported a memory problem on approximately 73% of days. Independent samples t tests revealed no significant differences between MCI and control participants for the total number of daily stressors, and chi-square analyses revealed no significant differences for the percentage of days reporting at least one stressor. There were also no significant differences in general stressor severity. As shown in Table 3, PWMCI reported a significantly greater number of memory prob lems and appraised them as more severe than did control partici pants.
Emotional Reactivity to Daily Stressors and Memory Problems General daily stressors. In analyses predicting NA, younger age was predictive of higher NA and was included as a covariate. The number of health problems was also included as a covariate because of group differences between MCI and CHOA partici pants. There was no main effect of WP stress predicting NA (see Table 4). However, there was a significant interaction effect of WP stress and MCI. The moderating effect of cognitive status on the relationship between daily stressors and NA is illustrated in Figure 1. These results suggest that the relationship between number of daily stressors and higher NA was significantly higher in the MCI group than in the control group. Similarly, the main effect of WP daily stressor severity predict ing NA was not significant, but the interaction of WP daily stressor severity and MCI was significantly predictive of higher NA. The
Table 2 Intercorrelations fo r All Study Variable fo r CHOAs (Above the Diagonal) and PWMCI (Below the Diagonal) Variable
1
1. Age 2. Gender 3. Education 4. Race 5. Marital status 6. Number of health problems 7. Number of general daily stressors (PM) 8. Severity of general daily stressors (PM) 9. Number of memory problems (PM) 10. Severity of memory problems (PM) 11. Negative affect (PM) 12. Positive affect (PM)
-.2 9 .17 .54* -.4 0 .30 -.4 0 -.52* -.2 3 -.31 -.3 2 -.1 3
Note. CHOAs interviews. ' p < .05.
—
2
3
4
5
6
7
8
9
10
11
12
-.2 5
.18 -.2 2
.62* -.2 5 .09
.19 -.3 9 .11 .26
.15-.0 8 .15 -.3 2 -.3 4
.21 -.0 6 -.23 .08 .05 .08
-.3 8 .06 -.3 0 -.31 -.3 4 .16 .54*
_
-.11 .11 -.3 7 .04 -.0 6 -.1 2 .66* .47*
.53* .29 .58* -.2 9
-.3 0 .08 -.44* -.1 0 -.0 8 -.15 .56* .59* .88*
.74* .44 -.2 0
-.3 5 -.0 2 -.2 3 -.1 4 -.3 5 .20 .22 .47* .22 .17
-.3 8 .00 .16 -.0 7 .32 .00 -.35 -.1 9 -.3 7 - 33 18
—
.05 -.1 9 -.41 -.58* .07 .19 .04 .26 -.1 6 .41
—
.08 .22 -.25 .01 -.0 6 -.0 5 -.2 6 -.2 2 .17
—
.08 .22 -.2 5 .01 -.0 6 -.0 5 .11 -.4 5
—
.65* .37 .27 .16 .00 .16 .16
___
.02 -.0 2 .05 -.0 9 .22 -.0 8
____
.69* .31 .05 .21 .07
.23 -.1 0
-.55*
cognitively healthy older adults; PWMCI — persons with mild cognitive impairment; PM = person mean over up to 8 days of daily
RICKENBACH, CONDEELIS, AND HALEY
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Table 3 Daily Affect, Daily General Stressors, and Daily Memory Problems by Cognitive Status Variable Daily psychological well-being Total daily PA (M ± SD) Total daily NA (M ± SD) Daily general stressors Total number of daily stressors (M ± SD) Days reported 1+ stressors (%) Average stressor severity® (M ± SD) Daily memory problems Total number of memory problems (M ± SD) Days reported 1 + memory problems (%) Memory problem severity (M ± SD)
All (N = 207 days)
PWMCI (n = 61 days)
CHOAs (n = 140 days)
P
15.16 ± 5.49 2.25 ± 4.01
13.10 ± 6.03 4.00 ± 6.03
16.15 ± 4.94 1.41 ± 2.09
Psychology and Aging 2015, Vol. 30, No. 2, 420-431
Daily Stressors and Emotional Reactivity in Individuals With Mild Cognitive Impairment and Cognitively Healthy Controls Elizabeth Hahn Rickenbach
Kristen L. Condeelis
Saint Anselm College
University of Alabama
William E. Haley University of South Florida Daily experiences of stress are common and have been associated with worse affect among older adults. People with mild cognitive impairment (PWMCI) have measurable memory deficits in between normal cognition and dementia and have been identified as having greater psychological distress than cognitively healthy older adults (CHOAs). Little is known about whether daily stressors contribute to distress among PWMCI. We hypothesized that compared with CHOAs, PWMCI would have higher daily negative affect and lower daily positive affect, report greater numbers and severity of daily stressors, and experience greater emotional reactivity to daily stressors. Fifteen clinically diagnosed PWMCI and 25 CHOAs completed daily reports of stressors, stressor severity, and positive and negative affect over an 8-day period. PWMCI reported higher daily negative affect, lower daily positive affect, and higher numbers and greater severity of memory stressors but did not differ from CHOAs in numbers or severity of general stressors. Cognitive status was a moderator of the daily stress-affect relationship. Days with greater numbers and severity of general daily stressors were associated with higher negative affect only for PWMCI. The numbers and severity of memory stressors were not associated with negative affect. In addition, more severe general daily stressors and memory stressors were associated with lower positive affect for all participants. Results suggest that PWMCI are less resilient in the face of daily stress than are CHOAs in terms of negative affect, perhaps because of declines in reserve capacity. The study presents a promising approach to understanding stress and coping in predementia states of cognition. Keywords: mild cognitive impairment, daily stress, daily affect
daily mood or emotional reactivity (DeLongis, Folkman, & Lazarus, 1988; Mroczek & Almeida, 2004). In addition, certain individuals may be more likely to experience greater stressorrelated increases in negative mood (i.e., greater emotional reactiv ity; Almeida, 2005). Past work suggests that individuals who are high in vulnerability to stress—for example, those high in neuroticism— may be more reactive to daily stress (Mroczek & Almeida, 2004). Mild cognitive impairment (MCI) is a diagnosis that has been developed with detailed diagnostic criteria (Petersen, 2004) and increasingly used in research and clinical settings such as memorydisorders clinics. In the latest edition of the American Psychiatric Association’s (2013) Diagnostic and Statistical Manual o f Mental Disorders (5th ed.), the diagnosis of mild neurocognitive disorder has been introduced. Mild neurocognitive disorder includes a broader spectrum of patients and does not currently have detailed published research diagnostic criteria, so the term MCI is more precise. People with MCI (PWMCI) have cognitive deficits that are not severe enough to merit a diagnosis of dementia, but they may be at risk for progression to dementia. By definition, PWMCI function fairly well, as evidenced by relatively intact activities of daily living (e.g., bathing, dressing themselves) and previous work stating that subtle differences in functioning may be difficult even for clinicians to ascertain (Petersen, 2004). However, PWMCI may be of particular interest as a group, because they may have differ-
There is extensive evidence that people who experience greater stress may be at risk for both worse psychological well-being and worse mental health (e.g., Lupien, McEwen, Gunnar, & Heim, 2009; Williams, Yan, Jackson, & Anderson, 1997). Stress may also be associated with momentary or short-term fluctuations in mood that occur within people over time (Bolger, Delongis, Kes sler, & Schilling, 1989). Thus, researchers interested in the role of stress in psychological aging have increasingly moved beyond using only global, retrospective reports of stress and well-being to also incorporate diary study designs, which provide benefits such as reducing recall bias and allowing for the examination of natu rally occurring fluctuations in a construct within people over time (Bolger, Davis, & Rafaeli, 2003). This research indicates that when people report greater daily stress, they also experience worse
This article was published Online First May 4, 2015. Elizabeth Hahn Rickenbach, Department of Psychology, Saint Anselm College; Kristen L. Condeelis, Department of Psychology, University of Alabama; William E. Haley, School of Aging Studies, University of South Florida. We thank Ross Andel, Amanda Smith, and Brent Small for providing their expertise and advice for this research project. Correspondence concerning this article should be addressed to Elizabeth Hahn Rickenbach, 100 Saint Anselm Drive, Box 1785, Manchester, NH 03102. E-mail: [email protected]
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DAILY STRESS IN MILD COGNITIVE IMPAIRMENT
ent experiences of stressors in daily life (e.g., difficulty managing a household or finances, interpersonal tension) than do cognitively healthy older adults (CHOAs) because of potential increased vul nerability. MCI is most commonly associated with deficits in memory and can be reliably assessed using neuropsychological assessments and clinical criteria (Albert et al., 2011; Petersen, 2004). PWMCI are at increased risk for development of Alzheimer’s disease (AD) compared with CHOAs. Conversion estimates, within a 5-year period, range from 26% to 50% of PWMCI, depending on the subtype of MCI (Fischer et al, 2007; Hanninen, Hallikainen, Tuomainen, Vanhanen, & Soininen, 2002). Although 11% of the population over the age of 65 is estimated to have Alzheimer’s disease (Alzheimer s Association, 2013), the prevalence of MCI, which varies widely by definition and study sample, is estimated to be between 22% and 71% (Ward, Arrighi, Michels, & Cedarbaum, 2012). By definition, PWMCI have memory impairment beyond that of CHOAs, but it does not reach the level of severity found in AD and does not significantly impair functioning or ability to perform daily activities (Albert et al., 2011). Research on well being among PWMCI has found that they have higher levels of depression and lower well-being than do CHOAs, but psycholog ical distress in MCI has often been conceptualized as a neuropsy chiatric symptom rather than within a more psychological frame work (e.g., Lyketsos et al., 2002). Moreover, the research has not considered daily affect; instead, most research has examined more stable experiences of well-being. The limited research to date on stress in MCI suggests that PWMCI experience frustration in their daily lives, difficulties in completing complex activities, and in terpersonal difficulties with family members that are focused on whether family members allow them to complete activities inde pendently, assist them with activities, or take control over certain complex activities (Blieszner, Roberto, Wilcox, Barham, & Win ston, 2007; Joosten-Weyn Banningh, Vemooij-Dassen, Olde Rikkert, & Teunisse, 2008; Mcllvane, Popa, Robinson, Houseweart, & Haley, 2008). Therefore, on the basis of past work (e.g., Blieszner et al., 2007), we hypothesized that greater memory difficulties associated with MCI may be associated with more daily stressors. Specifically, PWMCI and their spouses may report interpersonal tensions or the inability of the PWMCI to independently complete tasks of daily life, potentially resulting in home- or work-related stressors. There are a number of theoretical perspectives that could be useful in understanding daily stress and coping in PWMCI. For instance, PWMCI might experience more frequent daily stressors, including both general stressors and memory-related stressors, than do CHOAs because of their mild memory difficulties (i.e., reduced performance on neuropsychological tests). In addition, from a stress and coping perspective (Lazarus & Folkman, 1984), PWMCI might also appraise stressors as more stressful or severe if their coping resources are reduced because of diminished reserve capacity (Staudinger, Marsiske, & Baltes, 1993). Reserve capacity is a life-span developmental construct related to the idea that amid age-related declines, individuals have the capacity to cope with and adapt to losses. Certain factors, whether internal (e.g., cogni tive abilities) or external (e.g., support networks), contribute to reserve capacity (Staudinger, Marsiske, & Baltes, 1995), Thus, in the current study, we applied this theoretical framework to the investigation of whether individuals with reduced internal reserve
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capacity (i.e., those with MCI) are less able to avoid and cope with stressors in daily life. In other words, we hypothesized that with diminished resources (i.e., cognitive deficits associated with MCI), functioning will break down under high demand, leading to greater stressors and inability to cope with stressors. The strength and vulnerability integration model might also help to explain how older adults with MCI may be more likely to experience daily stressors and emotional distress than are CHOAs (Charles, 2010). This model posits that older adults reduce nega tive experiences and emotions in their daily lives in comparison with younger adults as a result of the effective use of strategies and behaviors. The cognitive deficits associated with MCI may disrupt effective strategy use, thus attenuating age-related benefits in emotional regulation. In line with these theoretical frameworks, PWMCI may expe rience greater fluctuations in daily affect when stressors occur, because evidence suggests that greater perceived stressor severity is associated with having fewer psychological resources. It is important to understand how PWMCI experience daily stressors and appraise them in comparison with CHOAs and to better recognize whether daily stressors are mechanisms through which PWMCI might experience poorer affect. We have not identified any studies that have used a short-term repeated measures design to examine intraindividual variation in naturally occurring experi ences of daily stress and affect in PWMCI and CHOAs. In com parison with retrospective measures, such methods have proven useful in providing a finer grained analysis of the experience of daily stress and memory problems in daily life. The current study used a novel approach to better understand daily stress processes and daily affect in PWMCI. Thus, it serves as a first step toward additional inquiry and understanding of the daily lives of individuals with MCI. Using a daily diary study design, we examined positive and negative affect, numbers of daily stressors (both general and memory specific), and perceived stressor severity in a sample of clinician-diagnosed PWMCI and CHOAs. To clarify, memory-specific daily stressors are instances such as forgetting the name of a friend or relative or forgetting the reason one entered a room, which are distinct from the memory deficits associated with MCI classification as operationalized by performance on neuropsychological tests. Both groups of partici pants included only individuals above a threshold on a measure of global cognitive status to ensure ability to complete daily diary measures. Covariates included demographic and health variables that might be related to daily stressors and affect. We initially examined daily experiences of affect, stressors, and stressor sever ity descriptively. First, on the basis of previous findings, we hypothesized that PWMCI would report higher average daily negative affect and lower average positive affect compared than would CHOAs. Second, we predicted that, on average, PWMCI would report more frequent memory problems than would CHOAs, but we did not predict whether the number of general daily stressors would differ between PWMCI and CHOAs. We also anticipated that, on average, PWMCI would appraise their general daily stressors and memory problems as more severe than would CHOAs because of their slightly reduced cognitive reserve capacity. Third, we examined emotional reactivity to both the numbers and the severity of daily stressors (general stressors and memory problems) and whether PWMCI and CHOAs differed in emotional reactivity. We defined emotional reactivity as worse
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affect (higher negative affect, lower positive affect) in response to daily stressors.
Method Sample and Recruitment The study included 15 PWMCI and 25 CHOAs recruited from the Alzheimer’s Disease Research Center (ADRC) at the Byrd Alzheimer’s Institute (Tampa, Florida). All study participants met the following inclusion criteria: (a) willing to complete a 1-hr baseline interview or mail-in questionnaire, (b) willing to complete eight consecutive days of 10-min phone interviews, (c) willing and able to give written informed consent, and (d) having scored at least 25 on a Mini-Mental State Examination (MMSE; Folstein, Folstein, & McHugh, 1975) or an equivalent score of 20 on the Telephone Interview for Cognitive Status (Brandt, Spencer, & Folstein, 1988). This latter criterion was included to comply with internal review board (IRB) procedures, to help ensure cognitive ability to provide informed consent, and to eliminate participants who might have developed dementia since their previous cognitive evaluations. Detailed descriptions of the MMSE and TICS are provided in the Baseline Interview Measures section. Participants with MCI met the following criteria: (a) seen by clinicians at the Byrd Alzheimer’s Center within the past year (ADRC assessments are conducted annually) and (b) given an MCI diagnosis at the previous visit, as determined by the ADRC diagnostic process. Participants who were cognitively healthy were required to meet those criteria and to have completed a neuropsychiatric evaluation at the Byrd Alzheimer’s Center to determine normal cognitive functioning within the past year. For all study participants, exclu sion criteria included the inability to speak and write in English. Compensation included the opportunity to win one of two $25 gift cards by lottery. The ADRC database includes individuals who have received extensive medical and neuropsychological evaluations. The data base includes approximately 110 CHOAs and 60 PWMCI. Of these, 99 who were identified by Byrd Institute staff as either having MCI or being controls and who participated in extensive neuropsychological testing during the current or previous year of the study were considered eligible for recruitment. Of those, a total of 60 (n = 34 [CHOA], n = 26 [PWMCI]) individuals agreed to be contacted by the current study’s research personnel, and, sub sequently, 40 agreed to participation and completed the study protocol (n = 25 [CHOA], n = 15 [PWMCI]). For the current study, the ADRC participants were asked if they were interested in participating in a “study on daily experiences of stress, health and aging.” Participants were told that “the purpose of this study is to find out how older adults deal with stress in their daily lives. We are also interested in understanding how hassles, bothersome events, or everyday problems with memory that occur in normal aging may make some people have worse mood.” As part of the current study and IRB-approved protocol, the classification as MCI or cognitively healthy participant willing to participate in the current study was provided to our research personnel. Results from chi-square analyses suggest that there were no significant differ ences between the two groups in their agreement to enroll in the study (p = .271). All study protocols were approved by the IRB at the University of South Florida.
Study Design Participants completed the informed consent and baseline inter view in person, when possible, and by mail if they lived more than an hour away. Within 2 weeks following the baseline interview, participants completed up to eight consecutive days of 10-min telephone interviews following a daily diary study design. Diary studies use self-reported measurements that participants complete multiple times over a short period of time, such as multiple times within a day, every day, or multiple times per week (Bolger et al., 1989). Events and experiences that meaningfully vary over a short period of time are intended for use in diary designs, because in these cases, there is variability to be measured and explained via daily reports (Affleck, Zautra, Tennen, & Armeli, 1999; Bolger et al., 2003). Participants completed daily interviews at a time con venient for them. Participants with MCI completed between four and five daily interviews (M = 4.67, SD = 2.53), and control participants completed between five and six daily interviews (M = 5.60, SD = 1.38). Independent samples t tests revealed no signif icant differences between the average number of interviews com pleted in MCI versus control participants {p = .127). The daily interviews lasted, on average, 7.29 min (SD = 1.83). PWMCI (M = 6.94 min, SD = 1.67) and CHOAs (M = 7.45 min, SD = 1.91) were not significantly different in the length of daily inter views (p = .437).
Determination of MCI A more detailed description of the criteria for MCI and the consensus conference for determination of MCI at the ADRC has been provided elsewhere (Duara et al., 2010; Schinka et al., 2010). In the ADRC study, participants and informants were interviewed for their clinical history. Participants also underwent clinical and neuropsychological evaluation, which included tests as part of the Uniform Data Set. As described in greater detail by previous publications (Morris et al., 2006; Weintraub et al., 2009), the Uniform Data Set includes tests of dementia severity (MMSE), attention (digit span forward and backward), processing speed (digit symbol), executive functioning (trail-making test), memory (e.g., immediate and delayed word recall), and language (category fluency, Boston Naming Test). MCI was determined through con sensus conference with trained geriatricians, neuropsychologists, and neurologists and followed previous research defining MCI as a state between normal cognitive aging and dementia (Petersen et al., 1999, 2003). Participants with MCI were identified as scoring 1.5 standard deviations below the mean on at least one cognitive domain for their age and education levels. Following Petersen’s (2004) criteria, they also met MCI criteria only if they showed no significant deficits in functional activities (e.g., bathing, dressing oneself). Participants were informed of their MCI diagnosis by clinicians as part of the ADRC study and were further classified as amnestic (memory domain affected) or nonamnestic (memory domain not affected) and single domain (only one domain af fected) or multiple domain (more than one domain affected). For the purposes of the current study and because of the small number of recently tested participants within each of the subtypes of MCI, the MCI subtypes were considered together as one group of MCI participants.
DAILY STRESS IN MILD COGNITIVE IMPAIRMENT
Baseline Interview Measures Basic demographic information. During the baseline inter view, demographic information, social factors, and health in formation were assessed. Demographic information included age, gender, education (highest level completed), race/ethnicity, and marital status. Additional information pertaining to social factors—such as current living arrangement, number of chil dren. and frequency with which the participant saw his or her children—was also assessed. During the baseline interview, participants were asked if a doctor had ever told them if they had any of five medical conditions (high blood pressure, cancer, heart problems, diabetes, and arthritis), and this information was used to create a sum score for the total number of health problems (range: 0-5). Global cognitive status. The MMSE (Folstein et al., 1975) was conducted during in-person baseline interviews. The MMSE covers multiple cognitive domains, and scores range from 0 to 30, with 30 being the best possible score. A widely used cutoff score of 25 (Borson, Scanlan, Chen, & Ganguli, 2003; Kim & Caine, 2002) served as a screening criterion to help ensure consenting capacity and was scored as in previous research (Fillenbaum, Hughes. Heyman, George, & Blazer, 1988). When the MMSE was not available from records or an in-person baseline interview was not conducted, participants completed the Telephone Interview of Cognitive Status (TICS; Welsh, Breitner, & Magruderhabib, 1993). The TICS-30 is an 11-item survey with scores ranging from 0 to 30, with higher scores indicating worse cognitive perfor mance. The TICS-30, which has been adapted from the TICS in previous research (Langa et al., 2005), is a global cognitive status instrument that has been found to be highly correlated with the MMSE (Desmond, Tatemichi, & Hanzawa, 1994). In the current study, a score of 20 on the TICS-30 was used as a cutoff as it has been determined to be equivalent to an MMSE score of 25 (Fong et al., 2009). For purposes of analyses, the TICS-30 scores were converted to MMSE scores on the basis of previous research (Fong et al., 2009). The TICS-30 and MMSE scores were not adjusted for education.
Daily Diary Measures Daily affect. Daily affect was assessed using a 12-item ver sion of the Positive and Negative Affect Schedule (PANAS; Wat son, Clark, & Tellegen, 1988), which includes six positive affect (PA) items (“cheerful,” “in good spirits,” “extremely happy,” “calm and peaceful,” “satisfied,” and “full of life”) and six nega tive affect (NA) items (“so sad nothing could cheer you up,” “nervous,” “restless or fidgety,” “worthless,” “hopeless,” and “that everything was an effort”). As part of the PANAS, participants were asked to report how much of the time during the past 24 hr they felt each of the items on a five-point scale: 0 (none of the time), 1 (a little of the time), 2 (some o f the time), 3 (most o f the time), or 4 (all o f the time). Scores were averaged for each scale, PA and NA, with higher scores indicating higher PA or NA (range: 0-4). Daily stressors. Participants were asked to report (yes/no) whether they had experienced any of 12 negative events within the past 24 hr. a scale adapted from previous research (Bolger et al., 1989; Cohen et al., 2008). Initially, participants were asked an open-ended question such as this: “Did anything particularly
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stressful happen during the past 24 hours?” Specific daily stressor questions followed the open-ended question and included inquiries concerning stress related to work, family demands, family mem bers being sick or injured, transportation, finances, spousal con flict, being ignored by a spouse, conflict with other family mem bers or friends, and avoiding activities because of health. The scale also incorporated two additional stressor questions: “Did someone do too much to help you with something?” and “Did someone not do enough to help you with something?” On the basis of past work (Blieszner et al., 2007; Joosten-Weyn Banningh et al., 2008), need for and receipt of support were hypothesized to be potentially relevant in a memory-impaired population. Consistent with previ ous daily diary research (Sliwinski, Almeida, Smyth, & Stawski, 2009), scores for total number of stressors (0-13) were summed for each day. To avoid repetition in counting events, the initial open-ended question was only included in the measure for total number of daily stressors if it was not included as a specific daily stressor in the follow-up questions. If the participant answered “yes” to experiencing a daily stres sor, he or she was then asked how severe the stressor was (i.e., how “stressful” the event was), with the following options: 0 {not at all), 1 {only a little), or 2 {a great deal). Participants who reported no stressor had a score of zero for stressor severity, and scores for the severity of events were summed for each day. Daily memory problems. Participants were asked seven questions pertaining to daily memory problems, a shortened ver sion of a 35-item measure (Sunderland, Harris, & Baddeley, 1983) adapted for daily format. The shortened format was similar to measures used in previous daily diary research in older adult populations (Neupert, Almeida, Mroczek, & Spiro. 2006). The seven questions, taken from the full questionnaire (Sunderland et al., 1983), were as follows: (a) “In the past 24 hours, did you go back to check whether you had done something that you meant to do?” (b) “In the past 24 hours, did you find that a word was ‘on the tip of your tongue,’ you knew what it was but could not quite find it?” (c) “In the past 24 hours, did you forget the names of friends or relatives or call them by the wrong names?” (d) “In the past 24 hours, did you forget something you had just said—maybe say, ‘What was I talking about?”’ (e) “In the past 24 hours, while reading, did you forget what the sentence is you have just read and have to reread it?” (f) “In the past 24 hours, did you forget where you had put something or lose something around the house?” (g) “In the past 24 hours, did you start to do something, then forget what it was you wanted to do—maybe saying, ‘What am I do ing?”’ Scores for memory problems were summed for each day and ranged from 0 to 7. Items were chosen on the basis of consultation with researchers with extensive experience in MCI, consensus, face validity, and examination of previously collected pilot data. If a participant answered “yes” to experiencing a memory prob lem, he or she was also asked a follow-up question to assess severity: “How stressful was that for you?” Similar to stressor severity, answer choices were 0 {not at all), 1 {only a little), or 2 {a great deal). Participants who reported no memory problems had a score of zero for stressor severity, and scores for the severity of events were summed for each day. The severity of memory prob lems was summed for each day.
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Statistical Approach For the first and second research aims, we compared daily affect, daily stressors, and daily stressor severity between PWMCI and CHOAs using independent samples t tests and chi-square analyses. For the third research aim, a series of multilevel models (MLMs) was conducted using PROC MIXED in SAS Version 9.2 to examine whether number and severity of stressors were predic tors of daily affect. MLMs have some specific advantages, includ ing the ability to handle missing data and to estimate variability within and between individuals (Affleck et al., 1999) by taking into account data that are hierarchical in nature, such as repeated measures within a person. MLM analyses included both Level-2 and Level-1 predictors of daily affect. Level-2 predictors included demographic factors (e.g., age, sex) in addition to the person mean or average of the daily diary data across up to 7 days. Level-1 predictors were nonaggregated data from each day of diary data. Level-1 predictors examined whether individuals had worse affect on days with greater daily stress, and Level-2 predictors examined whether individuals with greater stress, in general, had worse daily affect. In the within-person analyses, the total number of daily stressors and daily stressor severity were person-mean centered to examine the daily stressor in relation to a person’s average stress. The Level-2 predictors included the person mean for both the number and the severity of daily stressors across the eight daily diaries. Model specifications for all multilevel analyses included maximum likelihood estimation and an autoregressive covariance matrix to account for the dependency of data measured on days closer to each other versus farther apart. Also, intercept and time were considered random effects. Time was not included as a predictor in any of the analyses because it was not significantly correlated with any of the outcome measures and was not a variable of conceptual interest in the study. Predictors at Level 1 (e.g., number of stressors on a given day) and Level-2 person means (average number of daily stressors across up to 7 days) were both included, in line with past research, to better disaggregate the within-person and between-persons effects (Hoffman & Stawski, 2009). We conducted MLMs to examine (a) whether the number of daily stressors was associated with higher NA. (b) whether daily stressor severity was associated with higher NA, (c) whether the
number of memory problems was associated with higher NA. and (d) whether severity of memory problems was associated with higher NA. To estimate the moderating effect of MCI in the relationship between daily stressors and affect, we then added the interaction term of MCI and daily stressor number/severity. We then ran the same MLM, with PA as the outcome. Intraclass correlation coefficients were calculated to determine the variance in the Level-1 variables that was between persons (BP) and within person (WP). Unconditional models determined the following: general daily stressors (18% BP, 82% WP), memory stressors (58% BP, 42% WP), general stressor severity (9% BP, 91% WP), memory stressor severity (50% BP, 50% WP) PA (74% BP, 26% WP), and NA (82% BP, 18% WP). Power analyses were conducted for the sample size (N = 40) with two groups (15 MCI participants and 25 control participants) for Hypotheses 1 and 2; these included either daily estimates or baseline retrospective data. Post hoc power analyses estimated a power of .71 with a sample of 40 participants, a medium effect size (0.36), and a p value of .05. Because the current study also estimated regression coefficients using MLMs, primarily at Level 1 (daily stressors and daily memory problems) but also at Level 2, an effective sample size that considers the nature of hierarchical data was calculated on the basis of previous research (Savla, Roberto, Blieszner, Cox, & Gwazdauskas, 2011). For these anal yses, we used the 207 total days of analyses and an intraclass correlation coefficient of .60 to calculate an approximate effective sample size of 45 Level-2 units, consistent with previous research (Snijders, 2005), which yielded a statistical power of .74
Results On average, participants were 74 years old; 75% were White, and most were female, married, and had achieved more than a high school education (see Table 1). Most participants reported living with their spouse. Almost all had children, and half reported seeing their children weekly or daily. Participants reported, on average, two out of five health problems. MCI participants were signifi cantly more likely than controls to have more total health problems and to score lower on the MMSE. The two groups did not differ significantly on the other descriptive variables. The intercorrela-
Table 1 Descriptive Characteristics For Study Participants Variable
All (N = 40)
PWMCI (n = 15)
CHOAs (n = 25)
P
Age in years (M ± SD) Female (%) Education (% more than high school) Race (% White) Married (%) Living alone (%) Have children (%) See children regularly (% weekly or daily) Total number of health problems (M ± SD) MMSE score0 (M ± SD)
74.22 ± 6.45 75 80 75 65 30 95 50 1.99 ± 1.01 27.93 ± 1.53
75.33 ± 5.34 60 80 73.3 80 20 100 46.7 2.24 ± 1 .1 9 26.93 ± 1.44
73.56 ± 7.05 84 80 76 56 36 92 52 1.88 ± 0.89 28.52 ± 1.26
.407 .09 1 .85 .123 .274 .261 .202 .03 .001
Note. PWMCI = people with mild cognitive impairment; CHOAs = cognitive healthy older adults; MMSE = Mini-Mental State Examination. a For 12 participants, the Telephone Interview for Cognitive Status (TICS) was administered over the phone rather than MMSE, and TICS scores were converted to MMSE scores according to previous research (Fong et al., 2009).
DAILY STRESS IN MILD COGNITIVE IMPAIRMENT
tions for all study variables are displayed in Table 2, separately for PWMCI and CHOAs.
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interaction effect is illustrated in Figure 2 and suggests that on days when a person with MCI reported greater stressor severity than usual, he or she had significantly higher NA than did a control participant on a day when he or she reported greater stressor severity than usual. The interaction between the person mean of stressor severity and MCI was also significant, suggesting that greater stressor severity, on average, was associated with higher NA among PWMCI in particular. In analyses predicting PA, being married was predictive of higher PA and was included as a covariate. The number of health problems was also included as a covariate because of group differences between MCI and CHOA participants. The results for daily stressor numbers and severity in relation to PA are displayed in Table 4. The number of daily stressors was not related to PA, and there were no moderating effects of MCI. However, the person mean of the severity of stressors was related to PA, suggesting that participants who reported more severe stressors, on average, re ported lower PA. There was no moderating effect of the interaction of stressor severity and MCI predicting PA. Memory stressors. In analyses predicting NA, younger age was predictive of higher NA and was included as a covariate. The number of health problems was also included as a covariate because of group differences between MCI and CHOA partici pants. There was no main effect of the number of memory stressors in relation to NA; however, the interaction effect of PM memory stressors and MCI predicting NA was significant (see Table 5). This interaction effect is graphed in Figure 3 and suggests that reporting more daily stressors, on average, was associated with greater NA, especially among PWMCI. Memory stressor severity was not associated with NA, and there were no moderating effects of cognitive status. In analyses predicting PA, being married was predictive of higher PA and was included as a covariate. The number of health problems was also included as a covariate because of group differences between MCI and CHOA participants. When we ex amined daily memory problems predicting daily PA, results showed that greater numbers of memory problems (person means) were associated with lower PA (see Table 5). There was no significant interaction effect with MCI, suggesting that regardless
Daily Affect, Daily Stressors, and Stressor Severity Our first and second research aims examined daily affect, daily stressors, and severity of stressors for PWMCI and CHOAs. For the daily measures of affect, participants with MCI reported sig nificantly lower daily PA and significantly higher daily NA (see Table 3). Participants reported, on average, between one and two stressors each day, and they reported at least one stressor on approximately 74% of days. Participants reported between one and two memory problems per day, and they reported a memory problem on approximately 73% of days. Independent samples t tests revealed no significant differences between MCI and control participants for the total number of daily stressors, and chi-square analyses revealed no significant differences for the percentage of days reporting at least one stressor. There were also no significant differences in general stressor severity. As shown in Table 3, PWMCI reported a significantly greater number of memory prob lems and appraised them as more severe than did control partici pants.
Emotional Reactivity to Daily Stressors and Memory Problems General daily stressors. In analyses predicting NA, younger age was predictive of higher NA and was included as a covariate. The number of health problems was also included as a covariate because of group differences between MCI and CHOA partici pants. There was no main effect of WP stress predicting NA (see Table 4). However, there was a significant interaction effect of WP stress and MCI. The moderating effect of cognitive status on the relationship between daily stressors and NA is illustrated in Figure 1. These results suggest that the relationship between number of daily stressors and higher NA was significantly higher in the MCI group than in the control group. Similarly, the main effect of WP daily stressor severity predict ing NA was not significant, but the interaction of WP daily stressor severity and MCI was significantly predictive of higher NA. The
Table 2 Intercorrelations fo r All Study Variable fo r CHOAs (Above the Diagonal) and PWMCI (Below the Diagonal) Variable
1
1. Age 2. Gender 3. Education 4. Race 5. Marital status 6. Number of health problems 7. Number of general daily stressors (PM) 8. Severity of general daily stressors (PM) 9. Number of memory problems (PM) 10. Severity of memory problems (PM) 11. Negative affect (PM) 12. Positive affect (PM)
-.2 9 .17 .54* -.4 0 .30 -.4 0 -.52* -.2 3 -.31 -.3 2 -.1 3
Note. CHOAs interviews. ' p < .05.
—
2
3
4
5
6
7
8
9
10
11
12
-.2 5
.18 -.2 2
.62* -.2 5 .09
.19 -.3 9 .11 .26
.15-.0 8 .15 -.3 2 -.3 4
.21 -.0 6 -.23 .08 .05 .08
-.3 8 .06 -.3 0 -.31 -.3 4 .16 .54*
_
-.11 .11 -.3 7 .04 -.0 6 -.1 2 .66* .47*
.53* .29 .58* -.2 9
-.3 0 .08 -.44* -.1 0 -.0 8 -.15 .56* .59* .88*
.74* .44 -.2 0
-.3 5 -.0 2 -.2 3 -.1 4 -.3 5 .20 .22 .47* .22 .17
-.3 8 .00 .16 -.0 7 .32 .00 -.35 -.1 9 -.3 7 - 33 18
—
.05 -.1 9 -.41 -.58* .07 .19 .04 .26 -.1 6 .41
—
.08 .22 -.25 .01 -.0 6 -.0 5 -.2 6 -.2 2 .17
—
.08 .22 -.2 5 .01 -.0 6 -.0 5 .11 -.4 5
—
.65* .37 .27 .16 .00 .16 .16
___
.02 -.0 2 .05 -.0 9 .22 -.0 8
____
.69* .31 .05 .21 .07
.23 -.1 0
-.55*
cognitively healthy older adults; PWMCI — persons with mild cognitive impairment; PM = person mean over up to 8 days of daily
RICKENBACH, CONDEELIS, AND HALEY
426
Table 3 Daily Affect, Daily General Stressors, and Daily Memory Problems by Cognitive Status Variable Daily psychological well-being Total daily PA (M ± SD) Total daily NA (M ± SD) Daily general stressors Total number of daily stressors (M ± SD) Days reported 1+ stressors (%) Average stressor severity® (M ± SD) Daily memory problems Total number of memory problems (M ± SD) Days reported 1 + memory problems (%) Memory problem severity (M ± SD)
All (N = 207 days)
PWMCI (n = 61 days)
CHOAs (n = 140 days)
P
15.16 ± 5.49 2.25 ± 4.01
13.10 ± 6.03 4.00 ± 6.03
16.15 ± 4.94 1.41 ± 2.09
