Vol. 117 No. 6 June 2014
Influence of xerostomia on oral healtherelated quality of life in the elderly: a 5-year longitudinal study Kaori Enoki, DDS, PhD,a Ken-ich Matsuda, DDS, PhD,b Kazunori Ikebe, DDS, PhD,c Shunsuke Murai, DDS, PhD,d Minoru Yoshida, DDS, PhD,e Yoshinobu Maeda, DDS, PhD,f and William Murray Thomson, DDS, PhDg Osaka University Graduate School of Dentistry, Osaka, Japan; School of Dentistry, University of Otago, Dunedin, New Zealand
Objective. Xerostomia and tooth loss are major oral health problems in the elderly. The aim of this longitudinal study was to characterize the influence of xerostomia on oral healtherelated quality of life (OHRQoL) among elderly Japanese people. Study Design. A total of 99 community-dwelling, independently living individuals aged 60 years and older were interviewed and underwent dental examination at baseline and at a 5-year follow-up. The Oral Health Impact Profile-14 and the Xerostomia Inventory were used to assess OHRQoL and xerostomia severity, respectively. Results. Participants whose xerostomia worsened over the 5-year period had a significantly poorer follow-up OHRQoL. Linear regression models showed that tooth loss and worsening xerostomia were significant predictors of poorer follow-up OHRQoL. Conclusions. Tooth loss and worsening xerostomia result in poorer OHRQoL among older Japanese people. (Oral Surg Oral Med Oral Pathol Oral Radiol 2014;117:716-721)
Healthy aging is valued highly in Japanese society, and maintaining or improving quality of life (QoL) among older people is now a priority. Widely used to measure oral healtherelated QoL (OHRQoL) among older adults, the Oral Health Impact Profile (OHIP)1 is a 49-item questionnaire that is intended to measure the dysfunction, discomfort, and disability arising from oral conditions. A 14-item short form (the OHIP-14) was developed subsequently, and its properties are similar to those of the OHIP-49.2 Although survey findings reveal that OHRQoL is associated with self-assessed general health,
This work was supported by the Osaka University Scholarship for Short-term Overseas Research Activities 2010 and by a Grant-in-Aid for Scientific Research (No. 22592148 and 25870411) from Japan’s Society for the Promotion of Science. a Resident, Department of Removable Prosthodontics, Gerodontology, and Oral Rehabilitation, Osaka University Graduate School of Dentistry. b Assistant Professor, Department of Removable Prosthodontics, Gerodontology, and Oral Rehabilitation, Osaka University Graduate School of Dentistry. c Associate Professor, Department of Removable Prosthodontics, Gerodontology, and Oral Rehabilitation, Osaka University Graduate School of Dentistry. d Resident, Department of Removable Prosthodontics, Gerodontology, and Oral Rehabilitation, Osaka University Graduate School of Dentistry. e Visiting Academic Staff, Department of Removable Prosthodontics, Gerodontology, and Oral Rehabilitation, Osaka University Graduate School of Dentistry. f Professor, Department of Removable Prosthodontics, Gerodontology, and Oral Rehabilitation, Osaka University Graduate School of Dentistry. g Professor, Sir John Walsh Research Institute, Department of Oral Sciences, School of Dentistry, University of Otago. Received for publication Oct 22, 2013; returned for revision Feb 24, 2014; accepted for publication Mar 2, 2014. Ó 2014 Elsevier Inc. All rights reserved. 2212-4403/$ - see front matter http://dx.doi.org/10.1016/j.oooo.2014.03.001
716
dental status,3 masticatory performance,4 and dry mouth5,6 among older people, measures found to be valid and reliable in such cross-sectional studies cannot be assumed to be suitable for use in longitudinal research or in assessing the outcomes of clinical interventions.7 Moreover, quality of life is dynamic, and there are likely to be inter- and intraindividual variations, modified by individuals’ psychological characteristics.8 Determining the impact of changes in oral status or function on QoL is best done by observing changes within and among individuals over time, but the few such studies conducted to date9-12 have all involved relatively short follow-up periods, and there is a need for longer-term studies of oral status, function, and OHRQoL. Xerostomia is the subjective feeling of dry mouth, measured using either single-item approaches or with multi-item scales such as the Xerostomia Inventory (XI).13 Common among the elderly, chronic xerostomia affects speech, denture wearing, and the enjoyment and ingestion of food,6,14 and there is an accumulating body of evidence to show that xerostomia affects OHRQoL. Thomson et al.15 reported that chronic dry mouth is strongly and independently associated with poorer OHRQoL among relatively young (32-year-old) participants in a longstanding cohort study in which the XI
Statement of Clinical Relevance This longitudinal study confirms that dry mouth symptoms predict poorer oral healtherelated quality of life (OHRQoL). Our findings suggest that maintaining OHRQoL among older adults requires not only preventing tooth loss through appropriate oral management but also relieving symptoms of oral dryness.
OOOO Volume 117, Number 6
was not used. Locker reported that xerostomia was significantly associated with OHRQoL among older Canadians residing in nursing homes, whereas dental status was associated only with chewing capacity.6 Although there have been many cross-sectional studies of xerostomia, longitudinal studies are few,16-18 and no long-term follow-up studies have concurrently investigated oral status, salivary flow rate, xerostomia status, and OHRQoL. The aim of this study was to characterize the nature and antecedents of changes in xerostomia and the influence of xerostomia on OHRQoL in Japanese older adults over a 5-year period.
MATERIALS AND METHODS Study procedures The study protocol was approved by the Institutional Review Board of the Osaka University Graduate School of Dentistry. All participants were informed of the study aims and procedures, and interviews began only after consent forms had been signed. The study participants comprised community-dwelling, independently living volunteers aged over 60 years who attended weekly lectures (at the Senior Citizens’ College of Osaka) during 2005 in one of the adult education programs supported by the government of Osaka prefecture. The study purpose and procedures were explained to participants after an oral health lecture, and then data were collected by questionnaire and oral examination. Five years later, the original participants were contacted by mail and asked to undergo the same examination as in 2005. Those who gave consent took part in the follow-up study. Measures Data were collected on age, sex, and self-assessed general health at baseline and at follow-up. Dental examinations were conducted by calibrated dentists. The OHIP-14 includes 2 question items from each of 7 impact subdomains. These domains are organized to reflect the hierarchy of increasingly complex and disruptive problems. The first 3 domains, functional limitations, physical pain, and psychological discomfort, include items whose impact is limited to the individual’s experience, whereas items in the disability and handicap domains represent problems that may alter everyday activities and social roles. Response options and codes were “very often” (4), “fairly often” (3), “occasionally” (2), “hardly ever” (1), and “never” (0). OHIP-14 scores were obtained by summing the response codes for the 14 items, producing a single summary score for each respondent. The OHIP-14 scale had a range of 0 to 56, with higher scores indicating poorer OHRQoL. The methods used here are similar to those we reported previously.5,19
ORIGINAL ARTICLE Enoki et al. 717
The XI was used to obtain information on the severity of participants’ xerostomia symptoms. The XI is an 11-item summated rating scale that combines responses into a single continuous scale score, with higher scores representing more severe symptoms. Respondents were asked to choose 1 of 5 responses [“never” (1), “hardly ever” (2), “occasionally” (3), “fairly often” (4), and “very often” (5)] to 11 statements, with the reference period being the previous 4 weeks. The methods used here are similar to those we reported previously.18 The change in XI score was determined by subtracting the baseline score from the follow-up score. Clinically important changes in score were determined by identifying patients whose score changed by the minimally important difference (6 scale points or more).20 The question “How is your general health these days?” was used to collect information on self-assessed general health. The response options were “very good” (1), “good” (2), “fair” (3), “bad” (4), and “very bad” (5). The methods used here are similar to those we reported previously.5,19 Measurements of occlusal force and stimulated whole saliva flow rate (SSFR) (mL/min) were performed. Bilateral maximal occlusal force was recorded with pressure-sensitive sheets (Dental Prescale; Fuji Film GC Corp, Tokyo, Japan).19,21 Participants were asked to bite the sheet in the intercuspal position with as much force as possible for 3 seconds. Maximal occlusal force was computed using the associated analytical equipment (Occluzer FPD707; GC Corp, Tokyo, Japan). Stimulated whole saliva was collected by the mastication method, as reported previously.19,22 Participants were asked to chew a specific amount of paraffin wax (Orion Diagnostica, Finland) for 2 minutes and then spit into a tube. After collection, the volume of saliva was determined gravimetrically, assuming a specific gravity of 1.0. Changes in the number of teeth, occlusal force, and SSFR were determined by subtracting the follow-up value from that observed at baseline. Differences in means were tested for statistical significance using analysis of variance or, where appropriate, the MannWhitney U test. Differences in proportions were tested for statistical significance using a c2 test. The strength of the association between OHIP and XI scores at baseline (and between these scores and oral function, represented by occlusal force and SSFR) was determined using the Spearman rank correlation coefficient. Changes over time were tested for statistical significance using the Wilcoxon signed rank test. Three XI change groups were identified, based on the observed change in XI score (worsened, improved, or stable, according to the minimally important difference),20 after which their differences in OHIP score and SSFR
ORAL MEDICINE 718 Enoki et al.
OOOO June 2014
Table I. Comparison of baseline characteristics of those assessed and those lost to follow-up (total n ¼ 382) Lost to follow-up No. of persons (%) Female (%) Mean age (years; SD) Mean XI score (SD)* Mean OHIP score (SD)y Mean No. of teeth (SD) Mean SSFR (mL/min; SD)z Mean occlusal force (N; SD) General health good (%)
283 146 65.9 22.4 10.9 21.7 1.5 421.3 172
(74.1) (51.6) (4.2) (6.4) (8.1) (7.5) (1.0) (248.8) (60.8)
Table II. Comparison of characteristics at baseline and follow-up (n ¼ 99)
Assessed 99 46 65.4 22.6 9.3 24.5 1.5 498.3 65
(25.9) (46.5) (4.1) (6.1) (7.9) (6.2)z (1.0) (256.7)z (65.7)
OHIP, Oral Health Impact Profile; XI, Xerostomia Inventory; SSFR, stimulated saliva flow rate; OHRQoL, oral healtherelated quality of life. *Higher XI scores indicate more severe xerostomia. y Higher OHIP scores indicate poorer OHRQoL. z P < .05; Mann-Whitney U test.
were tested for statistical significance using the Kruskal-Wallis test (and using the Bonferroni correction for multiple comparison) because the data were not normally distributed. Differences in gender and tooth loss experience were tested for statistical significance using c2 tests. Linear regression models were developed for the follow-up XI and OHIP scores, controlling for the baseline XI and OHIP scores. Before that, the OHIP scores and XI scores were subjected to squareroot transformation to obtain normality. All analyses were conducted using IBM SPSS version 19 (IBM Japan, Tokyo, Japan).
RESULTS Of the 382 individuals who participated in the study at baseline, 51.6% were female, and the mean age was 66.0 years (SD, 4.2 years; range, 60-84 years). Participants’ mean XI score was 22.4 (SD, 6.4; range, 11-47), and the mean OHIP score was 10.9 (SD, 8.1; range, 10-48). Five years after the initial survey, 99 individuals (25.9%) consented to participate in the follow-up study. The differences between those lost to follow-up and those assessed at 5 years were determined (Table I). There were no significant differences in mean XI score, mean OHIP score, mean salivary flow rate, or selfassessed general health between those lost to follow-up and those assessed, but the latter had more remaining teeth and higher occlusal force, on average (see Table I). Data on the correlation between XI score, OHIP score, and other characteristics were obtained. The baseline XI score was positively correlated with the baseline OHIP score (rs ¼ 0.415; P < .001). The baseline XI score was negatively correlated with occlusal force and number of teeth, although the correlation coefficients were small. That is, those who
Baseline Mean Mean Mean Mean Mean
XI score (SD)* OHIP score (SD)y No. of teeth (SD) SSFR (SD) occlusal force (SD)
22.6 9.3 24.5 1.5 498.3
(6.1) (7.9) (6.2) (1.0) (256.7)
Follow-up 22.2 8.6 23.6 1.7 477.4
(6.5) (8.7) (6.5) (1.0) (274.3)
P .310 .169
Influence of xerostomia on oral healtherelated quality of life in the elderly: a 5-year longitudinal study Kaori Enoki, DDS, PhD,a Ken-ich Matsuda, DDS, PhD,b Kazunori Ikebe, DDS, PhD,c Shunsuke Murai, DDS, PhD,d Minoru Yoshida, DDS, PhD,e Yoshinobu Maeda, DDS, PhD,f and William Murray Thomson, DDS, PhDg Osaka University Graduate School of Dentistry, Osaka, Japan; School of Dentistry, University of Otago, Dunedin, New Zealand
Objective. Xerostomia and tooth loss are major oral health problems in the elderly. The aim of this longitudinal study was to characterize the influence of xerostomia on oral healtherelated quality of life (OHRQoL) among elderly Japanese people. Study Design. A total of 99 community-dwelling, independently living individuals aged 60 years and older were interviewed and underwent dental examination at baseline and at a 5-year follow-up. The Oral Health Impact Profile-14 and the Xerostomia Inventory were used to assess OHRQoL and xerostomia severity, respectively. Results. Participants whose xerostomia worsened over the 5-year period had a significantly poorer follow-up OHRQoL. Linear regression models showed that tooth loss and worsening xerostomia were significant predictors of poorer follow-up OHRQoL. Conclusions. Tooth loss and worsening xerostomia result in poorer OHRQoL among older Japanese people. (Oral Surg Oral Med Oral Pathol Oral Radiol 2014;117:716-721)
Healthy aging is valued highly in Japanese society, and maintaining or improving quality of life (QoL) among older people is now a priority. Widely used to measure oral healtherelated QoL (OHRQoL) among older adults, the Oral Health Impact Profile (OHIP)1 is a 49-item questionnaire that is intended to measure the dysfunction, discomfort, and disability arising from oral conditions. A 14-item short form (the OHIP-14) was developed subsequently, and its properties are similar to those of the OHIP-49.2 Although survey findings reveal that OHRQoL is associated with self-assessed general health,
This work was supported by the Osaka University Scholarship for Short-term Overseas Research Activities 2010 and by a Grant-in-Aid for Scientific Research (No. 22592148 and 25870411) from Japan’s Society for the Promotion of Science. a Resident, Department of Removable Prosthodontics, Gerodontology, and Oral Rehabilitation, Osaka University Graduate School of Dentistry. b Assistant Professor, Department of Removable Prosthodontics, Gerodontology, and Oral Rehabilitation, Osaka University Graduate School of Dentistry. c Associate Professor, Department of Removable Prosthodontics, Gerodontology, and Oral Rehabilitation, Osaka University Graduate School of Dentistry. d Resident, Department of Removable Prosthodontics, Gerodontology, and Oral Rehabilitation, Osaka University Graduate School of Dentistry. e Visiting Academic Staff, Department of Removable Prosthodontics, Gerodontology, and Oral Rehabilitation, Osaka University Graduate School of Dentistry. f Professor, Department of Removable Prosthodontics, Gerodontology, and Oral Rehabilitation, Osaka University Graduate School of Dentistry. g Professor, Sir John Walsh Research Institute, Department of Oral Sciences, School of Dentistry, University of Otago. Received for publication Oct 22, 2013; returned for revision Feb 24, 2014; accepted for publication Mar 2, 2014. Ó 2014 Elsevier Inc. All rights reserved. 2212-4403/$ - see front matter http://dx.doi.org/10.1016/j.oooo.2014.03.001
716
dental status,3 masticatory performance,4 and dry mouth5,6 among older people, measures found to be valid and reliable in such cross-sectional studies cannot be assumed to be suitable for use in longitudinal research or in assessing the outcomes of clinical interventions.7 Moreover, quality of life is dynamic, and there are likely to be inter- and intraindividual variations, modified by individuals’ psychological characteristics.8 Determining the impact of changes in oral status or function on QoL is best done by observing changes within and among individuals over time, but the few such studies conducted to date9-12 have all involved relatively short follow-up periods, and there is a need for longer-term studies of oral status, function, and OHRQoL. Xerostomia is the subjective feeling of dry mouth, measured using either single-item approaches or with multi-item scales such as the Xerostomia Inventory (XI).13 Common among the elderly, chronic xerostomia affects speech, denture wearing, and the enjoyment and ingestion of food,6,14 and there is an accumulating body of evidence to show that xerostomia affects OHRQoL. Thomson et al.15 reported that chronic dry mouth is strongly and independently associated with poorer OHRQoL among relatively young (32-year-old) participants in a longstanding cohort study in which the XI
Statement of Clinical Relevance This longitudinal study confirms that dry mouth symptoms predict poorer oral healtherelated quality of life (OHRQoL). Our findings suggest that maintaining OHRQoL among older adults requires not only preventing tooth loss through appropriate oral management but also relieving symptoms of oral dryness.
OOOO Volume 117, Number 6
was not used. Locker reported that xerostomia was significantly associated with OHRQoL among older Canadians residing in nursing homes, whereas dental status was associated only with chewing capacity.6 Although there have been many cross-sectional studies of xerostomia, longitudinal studies are few,16-18 and no long-term follow-up studies have concurrently investigated oral status, salivary flow rate, xerostomia status, and OHRQoL. The aim of this study was to characterize the nature and antecedents of changes in xerostomia and the influence of xerostomia on OHRQoL in Japanese older adults over a 5-year period.
MATERIALS AND METHODS Study procedures The study protocol was approved by the Institutional Review Board of the Osaka University Graduate School of Dentistry. All participants were informed of the study aims and procedures, and interviews began only after consent forms had been signed. The study participants comprised community-dwelling, independently living volunteers aged over 60 years who attended weekly lectures (at the Senior Citizens’ College of Osaka) during 2005 in one of the adult education programs supported by the government of Osaka prefecture. The study purpose and procedures were explained to participants after an oral health lecture, and then data were collected by questionnaire and oral examination. Five years later, the original participants were contacted by mail and asked to undergo the same examination as in 2005. Those who gave consent took part in the follow-up study. Measures Data were collected on age, sex, and self-assessed general health at baseline and at follow-up. Dental examinations were conducted by calibrated dentists. The OHIP-14 includes 2 question items from each of 7 impact subdomains. These domains are organized to reflect the hierarchy of increasingly complex and disruptive problems. The first 3 domains, functional limitations, physical pain, and psychological discomfort, include items whose impact is limited to the individual’s experience, whereas items in the disability and handicap domains represent problems that may alter everyday activities and social roles. Response options and codes were “very often” (4), “fairly often” (3), “occasionally” (2), “hardly ever” (1), and “never” (0). OHIP-14 scores were obtained by summing the response codes for the 14 items, producing a single summary score for each respondent. The OHIP-14 scale had a range of 0 to 56, with higher scores indicating poorer OHRQoL. The methods used here are similar to those we reported previously.5,19
ORIGINAL ARTICLE Enoki et al. 717
The XI was used to obtain information on the severity of participants’ xerostomia symptoms. The XI is an 11-item summated rating scale that combines responses into a single continuous scale score, with higher scores representing more severe symptoms. Respondents were asked to choose 1 of 5 responses [“never” (1), “hardly ever” (2), “occasionally” (3), “fairly often” (4), and “very often” (5)] to 11 statements, with the reference period being the previous 4 weeks. The methods used here are similar to those we reported previously.18 The change in XI score was determined by subtracting the baseline score from the follow-up score. Clinically important changes in score were determined by identifying patients whose score changed by the minimally important difference (6 scale points or more).20 The question “How is your general health these days?” was used to collect information on self-assessed general health. The response options were “very good” (1), “good” (2), “fair” (3), “bad” (4), and “very bad” (5). The methods used here are similar to those we reported previously.5,19 Measurements of occlusal force and stimulated whole saliva flow rate (SSFR) (mL/min) were performed. Bilateral maximal occlusal force was recorded with pressure-sensitive sheets (Dental Prescale; Fuji Film GC Corp, Tokyo, Japan).19,21 Participants were asked to bite the sheet in the intercuspal position with as much force as possible for 3 seconds. Maximal occlusal force was computed using the associated analytical equipment (Occluzer FPD707; GC Corp, Tokyo, Japan). Stimulated whole saliva was collected by the mastication method, as reported previously.19,22 Participants were asked to chew a specific amount of paraffin wax (Orion Diagnostica, Finland) for 2 minutes and then spit into a tube. After collection, the volume of saliva was determined gravimetrically, assuming a specific gravity of 1.0. Changes in the number of teeth, occlusal force, and SSFR were determined by subtracting the follow-up value from that observed at baseline. Differences in means were tested for statistical significance using analysis of variance or, where appropriate, the MannWhitney U test. Differences in proportions were tested for statistical significance using a c2 test. The strength of the association between OHIP and XI scores at baseline (and between these scores and oral function, represented by occlusal force and SSFR) was determined using the Spearman rank correlation coefficient. Changes over time were tested for statistical significance using the Wilcoxon signed rank test. Three XI change groups were identified, based on the observed change in XI score (worsened, improved, or stable, according to the minimally important difference),20 after which their differences in OHIP score and SSFR
ORAL MEDICINE 718 Enoki et al.
OOOO June 2014
Table I. Comparison of baseline characteristics of those assessed and those lost to follow-up (total n ¼ 382) Lost to follow-up No. of persons (%) Female (%) Mean age (years; SD) Mean XI score (SD)* Mean OHIP score (SD)y Mean No. of teeth (SD) Mean SSFR (mL/min; SD)z Mean occlusal force (N; SD) General health good (%)
283 146 65.9 22.4 10.9 21.7 1.5 421.3 172
(74.1) (51.6) (4.2) (6.4) (8.1) (7.5) (1.0) (248.8) (60.8)
Table II. Comparison of characteristics at baseline and follow-up (n ¼ 99)
Assessed 99 46 65.4 22.6 9.3 24.5 1.5 498.3 65
(25.9) (46.5) (4.1) (6.1) (7.9) (6.2)z (1.0) (256.7)z (65.7)
OHIP, Oral Health Impact Profile; XI, Xerostomia Inventory; SSFR, stimulated saliva flow rate; OHRQoL, oral healtherelated quality of life. *Higher XI scores indicate more severe xerostomia. y Higher OHIP scores indicate poorer OHRQoL. z P < .05; Mann-Whitney U test.
were tested for statistical significance using the Kruskal-Wallis test (and using the Bonferroni correction for multiple comparison) because the data were not normally distributed. Differences in gender and tooth loss experience were tested for statistical significance using c2 tests. Linear regression models were developed for the follow-up XI and OHIP scores, controlling for the baseline XI and OHIP scores. Before that, the OHIP scores and XI scores were subjected to squareroot transformation to obtain normality. All analyses were conducted using IBM SPSS version 19 (IBM Japan, Tokyo, Japan).
RESULTS Of the 382 individuals who participated in the study at baseline, 51.6% were female, and the mean age was 66.0 years (SD, 4.2 years; range, 60-84 years). Participants’ mean XI score was 22.4 (SD, 6.4; range, 11-47), and the mean OHIP score was 10.9 (SD, 8.1; range, 10-48). Five years after the initial survey, 99 individuals (25.9%) consented to participate in the follow-up study. The differences between those lost to follow-up and those assessed at 5 years were determined (Table I). There were no significant differences in mean XI score, mean OHIP score, mean salivary flow rate, or selfassessed general health between those lost to follow-up and those assessed, but the latter had more remaining teeth and higher occlusal force, on average (see Table I). Data on the correlation between XI score, OHIP score, and other characteristics were obtained. The baseline XI score was positively correlated with the baseline OHIP score (rs ¼ 0.415; P < .001). The baseline XI score was negatively correlated with occlusal force and number of teeth, although the correlation coefficients were small. That is, those who
Baseline Mean Mean Mean Mean Mean
XI score (SD)* OHIP score (SD)y No. of teeth (SD) SSFR (SD) occlusal force (SD)
22.6 9.3 24.5 1.5 498.3
(6.1) (7.9) (6.2) (1.0) (256.7)
Follow-up 22.2 8.6 23.6 1.7 477.4
(6.5) (8.7) (6.5) (1.0) (274.3)
P .310 .169
