Maturiras. 14 (1992) 161-169 Elsevier Scientific Publishers Ireland
Ltd.
MAT 00647
Consistency of perimenopausal estrogen use reporting by women in a population-based prospective study Mary L. Jannausch
and MaryFran
R. Sowers
Department II/ Epidemiology. University of Michigan. Ann Arbor. Michigan 48109 (Cf. S. A. i (Received
The authors
May 9, 1991; revision
assessed
the accuracy
received June 27, 1991; accepted
of perimenopausal
estrogen
use reporting
July 5, 1991)
by 430 women in a pro-
spective study of bone health risk factors. Data from two time points 5 years apart indicated that 383 (89%) women could consistently report having ever used perimenopausal estrogens or not. Of the 383. I38 reported some lifetime perimenopausal estrogen use; 97 (70%) of these consistently reported duration of use. The age-adjusted relative odds that women would misreport having ever used perimenopausal estrogens was II.7 (1.3, 100.6) for women with I I-20 years since last use, and 22.2 (1.8. 277.4) for ?I + years. Among women who inconsistently reported ever use of perimenopausal estrogen, the relative odds of reporting use at baseline and never use at follow-up as compared to reporting the converse by women aged 70-75 was 8.1 (1.2, 53.2) times that for women aged 60-69 at follow-up, and increased to 9.6 (I .8, 49.9) for women aged 76-85. This suggests that women can consistently report perimenopausal estrogen use, but accurate report of use declines in women whose last use precedes the interview by over IO years. Accurate report of duration or dates of perimenopausal estrogen use may be compromised in women of more advanced age.
Key words: epidemiologic
methods;
estrogens:
evaluation
studies:
interviews:
memory;
menopause
Introduction Although women’s reporting of menstrual patterns and reproductive events [l-4] and of medication use [5-71 have been studied for inconsistencies, longitudinal evaluation for reporting of perimenopausal estrogen use has not been described. Reporting of perimenopausal estrogen use is important because of estrogen’s controversial and multifactorial roles in bone density, heart disease and cancer in women [8]. The objective of this report is to describe the observed consistency of self-reports of past perimenopausal estrogen use gathered across time periods and estimate frequency of consistent estrogen use report. Correspondence to; MaryFran R. Sowers, The University of Michigan. Department School of Public Health, 109 S. Observatory St., Ann Arbor, Ml 48109. U.S.A. 037%5122/92/%05.00 Printed
and Published
0
1992 Elsevier Scientific in Ireland
Publishers
Ireland
Ltd
of Epidemiology.
162
Materials and Methods The study population has been previously described [9]. It consists of women from 3 rural communities in northwestern Iowa who participated in a longitudinal study of bone health risk factors with baseline observation in 1983-84 and follow-up 5 years later. According to Census data from 1970 and 1980, the communities were similar with respect to population size (approx. 1500 persons), age distribution, proportion foreign-born (16% Anglo-Saxon), mean income (approx. $8500 annually) and occupational categories. Women were eligible for the baseline study if they had lived in their respective communities for at least 5 years and if they consumed municipal water. All participants were ambulatory and able to give informed consent. All eligible women were of northern European heritage, most were either married (50.5%) or widowed (43.50/o), and most (87.0%) had experienced at least one live birth. There were no marital, parous, or ethnic differences between the communities. More than 80% of women eligible for the study of bone health participated in that study and constitute the study population for this report. Of the 827 women studied, 397 were excluded from this analysis because they were premenopausal (n = 169), had no second data point because of death (n = 34), migration (n = 63), or refusal to participate (n = 40), or were less than 55 years of age at baseline (n = 91). This report reflects the responses of the remaining 430 women. Each woman was asked about her menopausal status and perimenopausal estrogen use by a trained interviewer at two points in time 5 years apart. At each point in time, the woman was asked to respond categorically whether she was currently taking perimenopausal estrogens and whether she had ever used perimenopausal estrogens previously. All women were asked to report dates of use, including multiple intervals of use, for the period preceeding baseline and for the period between baseline and follow-up. Based on their replies, the women were grouped into 4 categories: consistent report at baseline and followup interviews; duration misclassification; no or wrong dates; and ever use inconsistency. These categories are described in the following paragraphs. Consistent respondents (n = 342) gave non-conflicting reports at two points in time as to whether or not they had ever used perimenopausal estrogens. They were consistent as to whether or not they had used estrogens for 2 years or more, and they could provide the years they began and stopped taking estrogens. Women categorized as having duration misclassification (n = 28) reported at both interviews that they had used or continued to use perimenopausal estrogen products. They were inconsistent as to whether duration of use was more than 2 years, but the inconsistency was limited to a reasonable error of f 2 years. Women with no or wrong dates of use (n = 13) consistently reported current and/or past use of perimenopausal estrogens. They either could not report the years corresponding to the start or end of estrogen therapy, or they reported years of use which substantially conflicted with other related information about baselinereported age of menopause or duration of use. Women in the ever use inconsistency category (n = 47) made one of two types of error. First, they may have reported using perimenopausal estrogens at baseline, and then denied any past use at follow-up. Alternately, they may have claimed no past
163
use at baseline, but at follow-up reported past use that substantially predated the baseline survey. Statistical methods General linear models were fit to test the relationships between report category and each of these variables: age at follow-up; age at menopause; years since menopause; duration of perimenopausal estrogen use in years; and, years since last perimenopausal estrogen use. Women who reported never using perimenopausal estrogens at follow-up were excluded from all models that assess duration of use or years since last use. The model for duration of use was adjusted for age. A x*-test was applied to evaluate the relationship between type of menopause and report categories. Logistic regression was performed to assess the probability of perimenopausal estrogen use misrecall or to assess the probability of use misclassification type, and to characterize those probabilities as an odds ratio [lo]. A K statistic was calculated to measure the level of agreement between baseline and follow-up ever use of perimenopausal estrogen overall and for each community [ 121. Rt?SUltS
The study subjects (n = 430) ranged in age from 60 to 85 years at follow-up, with a mean of 7 1.8 f 7.1 years. All women were reportedly postmenopausal. The mean age at menopause was 47.4 f 6.0 years at follow-up, with a mean of 24.3 f 9.0 years elapsed since menopause. Menopause was natural in 68% of the participants, and surgical in the other 32%. The overall mean perimenopausal estrogen use was 5.4 f 7.0 years at followup, with a mean of 14.6 f 11.5 years elapsed since last estrogen use. Kappa statistics were calculated to examine the possibility for misclassification on ever-use of perimenopausal estrogens, as assessed at follow-up. Since the chance for ever use inconsistency tends to increase with the prevalence of use in a population, a K statistic was calculated for each community. The results indicate a reasonably high level of agreement (75%) between reported ever use at baseline and reported
TABLE
I
FREQUENCIES OF ERRORS IN LONGITUDINAL REPORTING OF ESTROGEN USE, OVER ALL WOMEN (n = 430) AND BY COMMUNITY Community
Response
PERIMENOPAUSAL GROUP
classification No/wrong dates
Ever use inconsistency
3 9
3 2
10 19
119
16
8
18
342
28
13
41
Number eligible
Consistent
1 2
121 148
105 118
3
161
Totals
430
Duration misclassification
‘
164
TABLE II SELECTED CHARACTERISTICS Variable
OF WOMEN WITH NATURAL OR SURGICAL MENOPAUSE
Type of menopause
Variable P value
Number Age at follow-up Age of menopause Years since menopause Years of estrogen use* Years since last estrogen use
Surgical Mean f S.E.**
Natural Mean f SE.**
134
289
71.2 f 0.6
71.9 f 0.4
0.3898
43.3
49.3
0.3
0.0001
28.0 f 0.7
22.6 f 0.5
0.0001
7.3 zt 0.8
3.6 f 0.8
0.0012
16.0 f 1.3
0.1263
13.1
?? 0.5
??
1.3
??
*Adjusted for baseline age. **Least squares mean ?? standard error (mean).
ever use at follow-up. In addition, there was 80% agreement in community 1, where the ever-use prevalence was 421121 (3%) at follow-up; 72% in community 2, based on a prevalence of 611148 (40%) and 73% in community 3, with ever-use prevalence of 48/161 (30”/0). Reporting
error frequencies
As shown in Table I, we found that 89.1% ((342 + 28 + 13)/430) of the women were able to consistently report whether or not they had ever used perimenopausal estrogens; in contrast, 10.9% (47/430) could not classify themselves consistently as to ever-use. Of these 383 women who were consistent in their self-classification of their estrogen use, 138 women reported any past or present perimenopausal estrogen use. Of these users, 70 percent (971138) were consistent with regard to start/stop dates and duration of use. However, 28 women had duration misclussijkation and 13 women had no or wrong dutes. Furthermore, 245 (64%) of the 383 women consistently reported having never used perimenopausal estrogens. Because type of menopause, natural or surgical, might be a confounding factor in consistency of response, we examined characteristics associated with menopause type. As shown in Table II, no significant relationship was found between type of menopause and age at follow-up (P = 0.3898). However, women who had surgical menopause were younger at menopause (P = O.OOOl),had a longer mean time since menopause (P = O.OOOl),and had taken perimenopausal estrogens for a longer mean period of time (P = 0.0050) after age-adjustment, than did women who reported having a natural menopause. While women who had surgical menopause also had a slightly shorter mean time since last use, the difference was not significant (p = 0.1263).
III
***Adjusted
for baseline
OF
USE AND
14.0 *
age.
error
1.2
6.0 zt 0.7
24.0 zt 0.3 1.3 2.2
16.4 f
??
2.2
8.5 + 3.6
9.7
30.1 + 1.7
25.6 zt I.1 3.0 f
41.8 + 1.6
0.9
1.9 19.8 zt 3.2
2.8 f
24.2 * 0.9
47.6 f
0.3
47.7 f
zt 1.1
72.2 zt 1.0
75.2 + 1.9
61.4 f
0.4
71.9 f 46.0
34 (72%) 13 (28%)
Ever use inconsistency
VARIABLES**
4 (31%) 9 (69%)
No/wrong dates
MENOPAUSE-RELATED
17 (63%) 1.3
Duration misclassification
DURATION
11 (37%)
(mean).
AGE,
240 (72%) 95 (28%)
Consistent
*Least squares mean, f standard **Estimated at follow-up.
estrogen use*** Years since last estrogen use
menopause Years since menopause Duration of
Type of menopause Natural Surgery Age at follow-up Age of
Variable
COMPARISON OF MEAN + S.E.* RESPONSE CATEGORY (n = 430)
TABLE BETWEEN
0.0942
0.0324
0.0029
0.0031
0.0024
0.0001
Variable P value
WOMEN
IN EACH
166 TABLE IV ODDS OF CLASSIFYING A RESPONDENT INTO THE LISE MISCLASSIFICATION CATEGORY ADJUSTED FOR BASELINE AGE WITH THE CONSISTENT GROUP AS REFERENT (n = 1ll)f Odds ratio (95% CI)
Years since last use
I.0
< II
11-20 > 20
11.66 (1.3, 100.6) 22.22 (1.8, 277.4)
*Log odds are based upon 97 women in the consistent category, and 14 women in the use misclassification category, who reported current or past perimenopausal estrogen use at followup.
Women in the no or wrong dates and duration misclassification response categories were found to have a higher rate of surgical menopause (P = O.OOOl),as shown in Table III. There was a significant difference in follow-up age (P = 0.0024), mean age at menopause (P = 0.0031) and mean years since menopause (P = 0.0029) by the response categories. A weak relationship was found between the response categories and age-adjusted duration of estrogen use (P = 0.0324); however, there was a significant difference in years since last use (P = 0.0004). These differences were primarily attributable to women in the no or wrong dates category. These women tended to be older, to experience menopause earlier, have a longer mean time since menopause, and take perimenopausal estrogen(s) for greater lengths of time when compared to all other report categories.
TABLE V SELECTED CHARACTERISTICS OF WOMEN WITH TYPE 1 (n = 14) OR TYPE 2 (n = 30) GROUP RESPONSES, WITHIN THE EVER USE INCONSISTENCY Variable
Age at follow-up Age of menopause Years since menopause* Type of menopause Natural Surgery
Variable P value
Response type Type 1 (No/Yes) Mean ?? S.E.**
Type 2 (Yes/No) Mean f SE.**
67.6 f
73.9
1.3
0.0072
45.2 f 1.9
48.3 zt 1.3
0.1822
26.2 f 2.0
23.7 zt 1.3
0.3021
10 (71%) 4 (29%)
22 (73%) 8 (27%)
0.8960***
1.8
*Model is age-adjusted. **Least squares mean f standard error (S.E.). ***Mantel-Haenszel x2 P value.
??
167
Comparisons of the mean values between women in the consistent and ever use inconsistency groups were not significant with the exception of years since last use. In that model, women in the ever use inconsistency group reported a substantially longer mean period since last perimenopausal estrogen use. The probability of classification into the ever use inconsistency group was evaluated by age-adjusted logistic regression, with the consistent group as referent (P = 0.0048). The odds of ever use inconsistency increased linearly and significantly with time since last use (Table IV). The ever use inconsistency group was split into two subgroups for additional evaluation. Women who denied ever use of perimenopausal estrogens at baseline but contradicted that response at follow-up were labeled Type 1 (n = 14). Women who declared past use at baseline and denied ever use at follow-up were labeled Type 2 (n = 30). Three women were excluded from this analysis because they had reported they didn’t know whether they had taken estrogens, and thus could not be classified. As shown in Table V, women who gave a Type 2 (use at baseline/never use at followup) reply as compared to the converse Type 1 reply were more likely to be older (P = 0.0072). The relative odds of a Type 2 reply by women aged 70 to 75 were approximately 8 times (95% CI = 1.2, 53.2) that for women aged 60-69 at follow-up, and increased to 9.6 (95% CI = 1.8,49.9) for women aged 76 to 85. However, there was no observed difference in age at menopause (P = 0.1822), years since menopause (P = 0.3021) or frequency of type of menopause (P = 0.8960) between these two groups. Discussion Two previous studies [6,7] have evaluated the ability of women to report perimenopausal estrogen use. Beresford and Coker [6] compared spontaneous reporting of perimenopausal estrogen use with reporting aided by pictorial display of estrogen preparations in postmenopausal women (n = 14) who had taken hormone replacement therapy for at least 6 months, and found that pictorial aids could double the number of women who could report the name and dosage of their preparation. Goodman et al. [7] evaluated the consistency between medical records and patient report of lifetime perimenopausal estrogen use in 1032 women, aged 45-74 years, and showed that women can successfully replicate physician record data with self-report. This study extends that work by evaluating the ability of a geographically-defined population of women to recall perimenopausal estrogen use at two time points 5 years apart. A reasonably high agreement between baseline and follow-up reports of ever use was observed, overall and by community. However, there were some interesting variations in the responses with substantial implications for the survey researcher. There were few distinctions between consistent reporters and women who made errors. Compared to the characteristics of the ever use inconsistency group, there was no significant difference in mean age, age at menopause, years since menopause, or years of perimenopausal estrogen use. The only clear distinctions between the two groups were the consistent respondents’ significantly shorter time since last estrogen use and lack of current estrogen use in the ever use inconsistency group. Generally,
168
length of time since last estrogen use was significantly related to the likelihood that a woman would forget having ever used perimenopausal estrogens at all. Comparison of all four classification categories revealed that interesting distinctions lay between the duration misclassification and no or wrong dates categories. Originally, these two groups were conceived as a single category, but differences in age- and estrogen use-related characteristics made their combination inadvisable. The primary similarity between the women in these two categories is that 67% of them had experienced surgical menopause, in contrast to 30% in each of the remaining two groups. However, other characteristics of women in the duration misclassification and no or wrong dates tended to differ. Women who gave no or wrong dates were more likely to be older and to have been taking perimenopausal estrogen for a relatively long time. In contrast, women in the duration misclassification category tended to be among the youngest of all respondents and had a shorter mean duration of use than did either the consistent or no or wrong dates groups. These results suggest that, among women who can recall any use, the consistency with which start and stop dates are reported may be influenced by age, type of menopause, and duration of use. In contrast to other studies which show substantial decline in reporting consistency after 6 months, these women were able to report ever use of perimenopausal estrogen in the 5-year time frame of this evaluation. However, consistent with other evaluations of participant report [ 111, the age-adjusted odds of classifying a respondent into the ever use inconsistency group increased dramatically with years since last use, with the consistent group as referent. The relative odds of being placed in the ever use inconsistency group was slight for women who had stopped using estrogens no more than 10 years ago. However, the relative odds increased to almost 12.0, for women with 1l-20 years since last use, and then to approximately 22.0 for women with 21+ years since last use. Examination of subgroup characteristics within the ever use inconsistency category revealed that a woman was more likely to report estrogen use at baseline and forget ever-use at follow-up if she was older. Given that a woman had been placed in the ever use inconsistency category, the relative odds of forgetting past use at follow-up were negligible for women aged 60-69 at follow-up. However, the relative odds increased substantially at approximately age 70-85. Women aged 76 to 85 were somewhat more likely to forget past use at follow-up than were women aged 70-75. No other age- or estrogen use-related characteristic distinguished women who forgot ever-use at baseline from those who forgot ever-use at follow-up. Conclusions
This study shows that women in a geographically-defined population can successfully replicate self-reports of estrogen use at two points in time 5 years apart, However, it also suggests that accurate report of duration or dates of perimenopausal estrogen use may be compromised in women of more advanced age. Accurate report of ever use may decline in women whose use may have been more than 10 years prior to interview.
169
References Bean JA, Leeper JD. Wallace RB. et al. Variations Epidemiol 1979; 109: 181-185.
in the reporting
of menstrual
histories.
Am J
Wilcox AJ. Horney LF. Accuracy of spontaneous abortion recall. Am J Epidemiol 1984; 120: 727-733. Tilley BC. Barnes AB. Bergstralh E. et al. A comparison of pregnancy history recall and medical records; implications for retrospective studies. Am J Epidemiol 1985; 121: 269-281. Damon A, Damon ST, Reed RB, et al. Age at menarche of mothers and daughters with a note on accuracy of recall. Hum Biol 41: 161-175. 1969. Paganini-Hill A, Ross RK. Reliability of recall of drug usage and other health-related information. Am J Epidemiol 1982; 116: 114-122. Beresford SA, Coker AL. Pictorially assisted recall of past hormone use in case-control studies, Am J Epidemiol 1989; 130: 202-205. Goodman MT, Nomura AM, Wilkens LR, Kolonel LN. Agreement between interview information and physician records on history of menopausal estrogen use. Am J Epidemiol 1990; 131: 815-825. Ernster VL, Bush TL, Huggins GR, Kelsey JL. Schottenfeld D. Benefits and risks of menopausal estrogen and/or progestin hormone use. Prev Med 1988 Mar; 17(2): 201-223. Sowers MF, Clark MK, Jannausch ML, Wallace RB. A prospective study of bone mineral content and fracture in communities with differential fluoride exposure. Am J Epidemiol 1991; 133 (7): 649-660. Schlesselman. J. Case-Control Studes. Oxford University Press, 1982; 235-239. Klein DN, Rubovits DR. The Reliability of Subjects’ Reports on Stressful Life Events Inventories: A Longitudinal Study. J Behav Med 1987; lO(5): 501-512. Kelsey JL, Thompson Press, 1986: 290-29
WD. Evans AS. Methods
I
in Observational
Epidemiology.
Oxford
University
Ltd.
MAT 00647
Consistency of perimenopausal estrogen use reporting by women in a population-based prospective study Mary L. Jannausch
and MaryFran
R. Sowers
Department II/ Epidemiology. University of Michigan. Ann Arbor. Michigan 48109 (Cf. S. A. i (Received
The authors
May 9, 1991; revision
assessed
the accuracy
received June 27, 1991; accepted
of perimenopausal
estrogen
use reporting
July 5, 1991)
by 430 women in a pro-
spective study of bone health risk factors. Data from two time points 5 years apart indicated that 383 (89%) women could consistently report having ever used perimenopausal estrogens or not. Of the 383. I38 reported some lifetime perimenopausal estrogen use; 97 (70%) of these consistently reported duration of use. The age-adjusted relative odds that women would misreport having ever used perimenopausal estrogens was II.7 (1.3, 100.6) for women with I I-20 years since last use, and 22.2 (1.8. 277.4) for ?I + years. Among women who inconsistently reported ever use of perimenopausal estrogen, the relative odds of reporting use at baseline and never use at follow-up as compared to reporting the converse by women aged 70-75 was 8.1 (1.2, 53.2) times that for women aged 60-69 at follow-up, and increased to 9.6 (I .8, 49.9) for women aged 76-85. This suggests that women can consistently report perimenopausal estrogen use, but accurate report of use declines in women whose last use precedes the interview by over IO years. Accurate report of duration or dates of perimenopausal estrogen use may be compromised in women of more advanced age.
Key words: epidemiologic
methods;
estrogens:
evaluation
studies:
interviews:
memory;
menopause
Introduction Although women’s reporting of menstrual patterns and reproductive events [l-4] and of medication use [5-71 have been studied for inconsistencies, longitudinal evaluation for reporting of perimenopausal estrogen use has not been described. Reporting of perimenopausal estrogen use is important because of estrogen’s controversial and multifactorial roles in bone density, heart disease and cancer in women [8]. The objective of this report is to describe the observed consistency of self-reports of past perimenopausal estrogen use gathered across time periods and estimate frequency of consistent estrogen use report. Correspondence to; MaryFran R. Sowers, The University of Michigan. Department School of Public Health, 109 S. Observatory St., Ann Arbor, Ml 48109. U.S.A. 037%5122/92/%05.00 Printed
and Published
0
1992 Elsevier Scientific in Ireland
Publishers
Ireland
Ltd
of Epidemiology.
162
Materials and Methods The study population has been previously described [9]. It consists of women from 3 rural communities in northwestern Iowa who participated in a longitudinal study of bone health risk factors with baseline observation in 1983-84 and follow-up 5 years later. According to Census data from 1970 and 1980, the communities were similar with respect to population size (approx. 1500 persons), age distribution, proportion foreign-born (16% Anglo-Saxon), mean income (approx. $8500 annually) and occupational categories. Women were eligible for the baseline study if they had lived in their respective communities for at least 5 years and if they consumed municipal water. All participants were ambulatory and able to give informed consent. All eligible women were of northern European heritage, most were either married (50.5%) or widowed (43.50/o), and most (87.0%) had experienced at least one live birth. There were no marital, parous, or ethnic differences between the communities. More than 80% of women eligible for the study of bone health participated in that study and constitute the study population for this report. Of the 827 women studied, 397 were excluded from this analysis because they were premenopausal (n = 169), had no second data point because of death (n = 34), migration (n = 63), or refusal to participate (n = 40), or were less than 55 years of age at baseline (n = 91). This report reflects the responses of the remaining 430 women. Each woman was asked about her menopausal status and perimenopausal estrogen use by a trained interviewer at two points in time 5 years apart. At each point in time, the woman was asked to respond categorically whether she was currently taking perimenopausal estrogens and whether she had ever used perimenopausal estrogens previously. All women were asked to report dates of use, including multiple intervals of use, for the period preceeding baseline and for the period between baseline and follow-up. Based on their replies, the women were grouped into 4 categories: consistent report at baseline and followup interviews; duration misclassification; no or wrong dates; and ever use inconsistency. These categories are described in the following paragraphs. Consistent respondents (n = 342) gave non-conflicting reports at two points in time as to whether or not they had ever used perimenopausal estrogens. They were consistent as to whether or not they had used estrogens for 2 years or more, and they could provide the years they began and stopped taking estrogens. Women categorized as having duration misclassification (n = 28) reported at both interviews that they had used or continued to use perimenopausal estrogen products. They were inconsistent as to whether duration of use was more than 2 years, but the inconsistency was limited to a reasonable error of f 2 years. Women with no or wrong dates of use (n = 13) consistently reported current and/or past use of perimenopausal estrogens. They either could not report the years corresponding to the start or end of estrogen therapy, or they reported years of use which substantially conflicted with other related information about baselinereported age of menopause or duration of use. Women in the ever use inconsistency category (n = 47) made one of two types of error. First, they may have reported using perimenopausal estrogens at baseline, and then denied any past use at follow-up. Alternately, they may have claimed no past
163
use at baseline, but at follow-up reported past use that substantially predated the baseline survey. Statistical methods General linear models were fit to test the relationships between report category and each of these variables: age at follow-up; age at menopause; years since menopause; duration of perimenopausal estrogen use in years; and, years since last perimenopausal estrogen use. Women who reported never using perimenopausal estrogens at follow-up were excluded from all models that assess duration of use or years since last use. The model for duration of use was adjusted for age. A x*-test was applied to evaluate the relationship between type of menopause and report categories. Logistic regression was performed to assess the probability of perimenopausal estrogen use misrecall or to assess the probability of use misclassification type, and to characterize those probabilities as an odds ratio [lo]. A K statistic was calculated to measure the level of agreement between baseline and follow-up ever use of perimenopausal estrogen overall and for each community [ 121. Rt?SUltS
The study subjects (n = 430) ranged in age from 60 to 85 years at follow-up, with a mean of 7 1.8 f 7.1 years. All women were reportedly postmenopausal. The mean age at menopause was 47.4 f 6.0 years at follow-up, with a mean of 24.3 f 9.0 years elapsed since menopause. Menopause was natural in 68% of the participants, and surgical in the other 32%. The overall mean perimenopausal estrogen use was 5.4 f 7.0 years at followup, with a mean of 14.6 f 11.5 years elapsed since last estrogen use. Kappa statistics were calculated to examine the possibility for misclassification on ever-use of perimenopausal estrogens, as assessed at follow-up. Since the chance for ever use inconsistency tends to increase with the prevalence of use in a population, a K statistic was calculated for each community. The results indicate a reasonably high level of agreement (75%) between reported ever use at baseline and reported
TABLE
I
FREQUENCIES OF ERRORS IN LONGITUDINAL REPORTING OF ESTROGEN USE, OVER ALL WOMEN (n = 430) AND BY COMMUNITY Community
Response
PERIMENOPAUSAL GROUP
classification No/wrong dates
Ever use inconsistency
3 9
3 2
10 19
119
16
8
18
342
28
13
41
Number eligible
Consistent
1 2
121 148
105 118
3
161
Totals
430
Duration misclassification
‘
164
TABLE II SELECTED CHARACTERISTICS Variable
OF WOMEN WITH NATURAL OR SURGICAL MENOPAUSE
Type of menopause
Variable P value
Number Age at follow-up Age of menopause Years since menopause Years of estrogen use* Years since last estrogen use
Surgical Mean f S.E.**
Natural Mean f SE.**
134
289
71.2 f 0.6
71.9 f 0.4
0.3898
43.3
49.3
0.3
0.0001
28.0 f 0.7
22.6 f 0.5
0.0001
7.3 zt 0.8
3.6 f 0.8
0.0012
16.0 f 1.3
0.1263
13.1
?? 0.5
??
1.3
??
*Adjusted for baseline age. **Least squares mean ?? standard error (mean).
ever use at follow-up. In addition, there was 80% agreement in community 1, where the ever-use prevalence was 421121 (3%) at follow-up; 72% in community 2, based on a prevalence of 611148 (40%) and 73% in community 3, with ever-use prevalence of 48/161 (30”/0). Reporting
error frequencies
As shown in Table I, we found that 89.1% ((342 + 28 + 13)/430) of the women were able to consistently report whether or not they had ever used perimenopausal estrogens; in contrast, 10.9% (47/430) could not classify themselves consistently as to ever-use. Of these 383 women who were consistent in their self-classification of their estrogen use, 138 women reported any past or present perimenopausal estrogen use. Of these users, 70 percent (971138) were consistent with regard to start/stop dates and duration of use. However, 28 women had duration misclussijkation and 13 women had no or wrong dutes. Furthermore, 245 (64%) of the 383 women consistently reported having never used perimenopausal estrogens. Because type of menopause, natural or surgical, might be a confounding factor in consistency of response, we examined characteristics associated with menopause type. As shown in Table II, no significant relationship was found between type of menopause and age at follow-up (P = 0.3898). However, women who had surgical menopause were younger at menopause (P = O.OOOl),had a longer mean time since menopause (P = O.OOOl),and had taken perimenopausal estrogens for a longer mean period of time (P = 0.0050) after age-adjustment, than did women who reported having a natural menopause. While women who had surgical menopause also had a slightly shorter mean time since last use, the difference was not significant (p = 0.1263).
III
***Adjusted
for baseline
OF
USE AND
14.0 *
age.
error
1.2
6.0 zt 0.7
24.0 zt 0.3 1.3 2.2
16.4 f
??
2.2
8.5 + 3.6
9.7
30.1 + 1.7
25.6 zt I.1 3.0 f
41.8 + 1.6
0.9
1.9 19.8 zt 3.2
2.8 f
24.2 * 0.9
47.6 f
0.3
47.7 f
zt 1.1
72.2 zt 1.0
75.2 + 1.9
61.4 f
0.4
71.9 f 46.0
34 (72%) 13 (28%)
Ever use inconsistency
VARIABLES**
4 (31%) 9 (69%)
No/wrong dates
MENOPAUSE-RELATED
17 (63%) 1.3
Duration misclassification
DURATION
11 (37%)
(mean).
AGE,
240 (72%) 95 (28%)
Consistent
*Least squares mean, f standard **Estimated at follow-up.
estrogen use*** Years since last estrogen use
menopause Years since menopause Duration of
Type of menopause Natural Surgery Age at follow-up Age of
Variable
COMPARISON OF MEAN + S.E.* RESPONSE CATEGORY (n = 430)
TABLE BETWEEN
0.0942
0.0324
0.0029
0.0031
0.0024
0.0001
Variable P value
WOMEN
IN EACH
166 TABLE IV ODDS OF CLASSIFYING A RESPONDENT INTO THE LISE MISCLASSIFICATION CATEGORY ADJUSTED FOR BASELINE AGE WITH THE CONSISTENT GROUP AS REFERENT (n = 1ll)f Odds ratio (95% CI)
Years since last use
I.0
< II
11-20 > 20
11.66 (1.3, 100.6) 22.22 (1.8, 277.4)
*Log odds are based upon 97 women in the consistent category, and 14 women in the use misclassification category, who reported current or past perimenopausal estrogen use at followup.
Women in the no or wrong dates and duration misclassification response categories were found to have a higher rate of surgical menopause (P = O.OOOl),as shown in Table III. There was a significant difference in follow-up age (P = 0.0024), mean age at menopause (P = 0.0031) and mean years since menopause (P = 0.0029) by the response categories. A weak relationship was found between the response categories and age-adjusted duration of estrogen use (P = 0.0324); however, there was a significant difference in years since last use (P = 0.0004). These differences were primarily attributable to women in the no or wrong dates category. These women tended to be older, to experience menopause earlier, have a longer mean time since menopause, and take perimenopausal estrogen(s) for greater lengths of time when compared to all other report categories.
TABLE V SELECTED CHARACTERISTICS OF WOMEN WITH TYPE 1 (n = 14) OR TYPE 2 (n = 30) GROUP RESPONSES, WITHIN THE EVER USE INCONSISTENCY Variable
Age at follow-up Age of menopause Years since menopause* Type of menopause Natural Surgery
Variable P value
Response type Type 1 (No/Yes) Mean ?? S.E.**
Type 2 (Yes/No) Mean f SE.**
67.6 f
73.9
1.3
0.0072
45.2 f 1.9
48.3 zt 1.3
0.1822
26.2 f 2.0
23.7 zt 1.3
0.3021
10 (71%) 4 (29%)
22 (73%) 8 (27%)
0.8960***
1.8
*Model is age-adjusted. **Least squares mean f standard error (S.E.). ***Mantel-Haenszel x2 P value.
??
167
Comparisons of the mean values between women in the consistent and ever use inconsistency groups were not significant with the exception of years since last use. In that model, women in the ever use inconsistency group reported a substantially longer mean period since last perimenopausal estrogen use. The probability of classification into the ever use inconsistency group was evaluated by age-adjusted logistic regression, with the consistent group as referent (P = 0.0048). The odds of ever use inconsistency increased linearly and significantly with time since last use (Table IV). The ever use inconsistency group was split into two subgroups for additional evaluation. Women who denied ever use of perimenopausal estrogens at baseline but contradicted that response at follow-up were labeled Type 1 (n = 14). Women who declared past use at baseline and denied ever use at follow-up were labeled Type 2 (n = 30). Three women were excluded from this analysis because they had reported they didn’t know whether they had taken estrogens, and thus could not be classified. As shown in Table V, women who gave a Type 2 (use at baseline/never use at followup) reply as compared to the converse Type 1 reply were more likely to be older (P = 0.0072). The relative odds of a Type 2 reply by women aged 70 to 75 were approximately 8 times (95% CI = 1.2, 53.2) that for women aged 60-69 at follow-up, and increased to 9.6 (95% CI = 1.8,49.9) for women aged 76 to 85. However, there was no observed difference in age at menopause (P = 0.1822), years since menopause (P = 0.3021) or frequency of type of menopause (P = 0.8960) between these two groups. Discussion Two previous studies [6,7] have evaluated the ability of women to report perimenopausal estrogen use. Beresford and Coker [6] compared spontaneous reporting of perimenopausal estrogen use with reporting aided by pictorial display of estrogen preparations in postmenopausal women (n = 14) who had taken hormone replacement therapy for at least 6 months, and found that pictorial aids could double the number of women who could report the name and dosage of their preparation. Goodman et al. [7] evaluated the consistency between medical records and patient report of lifetime perimenopausal estrogen use in 1032 women, aged 45-74 years, and showed that women can successfully replicate physician record data with self-report. This study extends that work by evaluating the ability of a geographically-defined population of women to recall perimenopausal estrogen use at two time points 5 years apart. A reasonably high agreement between baseline and follow-up reports of ever use was observed, overall and by community. However, there were some interesting variations in the responses with substantial implications for the survey researcher. There were few distinctions between consistent reporters and women who made errors. Compared to the characteristics of the ever use inconsistency group, there was no significant difference in mean age, age at menopause, years since menopause, or years of perimenopausal estrogen use. The only clear distinctions between the two groups were the consistent respondents’ significantly shorter time since last estrogen use and lack of current estrogen use in the ever use inconsistency group. Generally,
168
length of time since last estrogen use was significantly related to the likelihood that a woman would forget having ever used perimenopausal estrogens at all. Comparison of all four classification categories revealed that interesting distinctions lay between the duration misclassification and no or wrong dates categories. Originally, these two groups were conceived as a single category, but differences in age- and estrogen use-related characteristics made their combination inadvisable. The primary similarity between the women in these two categories is that 67% of them had experienced surgical menopause, in contrast to 30% in each of the remaining two groups. However, other characteristics of women in the duration misclassification and no or wrong dates tended to differ. Women who gave no or wrong dates were more likely to be older and to have been taking perimenopausal estrogen for a relatively long time. In contrast, women in the duration misclassification category tended to be among the youngest of all respondents and had a shorter mean duration of use than did either the consistent or no or wrong dates groups. These results suggest that, among women who can recall any use, the consistency with which start and stop dates are reported may be influenced by age, type of menopause, and duration of use. In contrast to other studies which show substantial decline in reporting consistency after 6 months, these women were able to report ever use of perimenopausal estrogen in the 5-year time frame of this evaluation. However, consistent with other evaluations of participant report [ 111, the age-adjusted odds of classifying a respondent into the ever use inconsistency group increased dramatically with years since last use, with the consistent group as referent. The relative odds of being placed in the ever use inconsistency group was slight for women who had stopped using estrogens no more than 10 years ago. However, the relative odds increased to almost 12.0, for women with 1l-20 years since last use, and then to approximately 22.0 for women with 21+ years since last use. Examination of subgroup characteristics within the ever use inconsistency category revealed that a woman was more likely to report estrogen use at baseline and forget ever-use at follow-up if she was older. Given that a woman had been placed in the ever use inconsistency category, the relative odds of forgetting past use at follow-up were negligible for women aged 60-69 at follow-up. However, the relative odds increased substantially at approximately age 70-85. Women aged 76 to 85 were somewhat more likely to forget past use at follow-up than were women aged 70-75. No other age- or estrogen use-related characteristic distinguished women who forgot ever-use at baseline from those who forgot ever-use at follow-up. Conclusions
This study shows that women in a geographically-defined population can successfully replicate self-reports of estrogen use at two points in time 5 years apart, However, it also suggests that accurate report of duration or dates of perimenopausal estrogen use may be compromised in women of more advanced age. Accurate report of ever use may decline in women whose use may have been more than 10 years prior to interview.
169
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