Vol. 109, No. 2
AMIEJCAN JOURNAL or EPIDEMIOLOGY
Copyright © 1979 by The Johns Hopkins University School of Hygiene and Public Health All rights reserved
Printed in USA.
VARIATIONS IN THE REPORTING OF MENSTRUAL HISTORIES JUDY A. BEAN,' JAMES D. LEEPER,' ROBERT B. WALLACE,1 BARRY M. SHERMAN3 AND HELEN JAGGER4 Bean, J. A. (Oept. of Preventive Medicine and Environmental Health, U. of Iowa, Iowa City, Iowa 52242), J. D. Leeper, R. B. Wallace, B. M. Sherman and H. Jagger. Variations In the reporting of menstrual histories. 4m J Epidemiol 109:181-185, 1979. This investigation examined the accuracy of recall of females to questions concerning ages at menarche, natural and surgical menopause, first use of oral contraceptives and mean menstrual cycle length and variance. A sample of 160 women who had recorded their menstrual and reproductive events as they occurred were administered a questionnaire concerning these events, with responses compared to the original data. For the variables age at menarche, age at natural menopause, age at surgical menopause and age at first use of oral contraceptives, the percentage of women who correctly recalled within a year ranged from 75% to 90%. Recollection of menstrual cycle length and variability by Interview was considered unreliable. These findings are encouraging regarding the ability to recall the age when certain menstrual and reproductive events occur, but not for menstrual cycle intervals or patterns. Because these women were well-educated and had once recorded study variables, these results might be considered optimal. menopause; menstruation; questionnaires; recall
Information regarding menarche, menstrual cycle patterns, menopause, oral contraceptive use and other menstrual and reproductive events collected by interview are of special interest in the study of fertility, population biology, family planning and breast cancer risk. Extensive evidence indicates that inaccuracies may occur in the recall of information, related to the nature of the question, length of recall, interview setting and other interview variables (1). In the present investigation, which was deReceived for publication March 6, 1978, and in final form July 25, 1978. 1 Department of Preventive Medicine and Environmental Health, University of Iowa, Iowa City, IA 52242 (address for reprint requests). 1 College of Community Health Sciences, University of Alabama, Tuscaloosa, AL. 1 Department of Internal Medicine, University of Iowa, Iowa City, IA. 4 Minnesota Health Department, Minneapolis, MN. This study was supported by grant #CA15104-02 from the National Cancer Institute.
signed to validate a questionnaire used in a case-control study of menstrual and reproductive antecedents of breast cancer, the accuracy of recall response of such variables was tested by comparing responses to a prospectively collected data set. METHODS
In 1934, Dr. Alan Treloar began the Menstrual and Reproductive History study (the MRH) by enrolling coeds at the University of Minnesota who agreed to record the dates of onset and cessation of menstrual flow, pregnancies, lactation, contraceptive use and related events (2). Over 500 persons reported their menstrual histories the first year, and 2000 more were added before the original panel was closed in 1938. From then until the present, data on menses of this original panel have been gathered continuously. In the 1940's a new panel was ini-
181
182
BEAN, LEEPER, WALLACE, SHERMAN AND JAGGER
tiated, and another one was started in the early 1960's, so that by 1970, 3780 women had participated in this study. In the protocol, a woman remains in the study as long as she wishes, or until she is lost through failure of mail contact or until menses ceases. Women living in the Minneapolis-St. Paul metropolitan area who had participated in the MRH study for at least five years were identified. The 425 women meeting these criteria were classified by age into three groups: 25-34, 35-44, and 45-64 years. Forty women were randomly selected in each of the first two age groups and 80 in the last. No woman refused the interview. The interview consisted of a structured questionnaire administered by a trained interviewer who collected information on demographic variables, year of menarche, year of menopause (when applicable), menstrual cycle length and variability, number of cycles over 42 days and less than 21 days, age at hysterectomy, age at onset of oral contraceptive use, number of pregnancies and other events. The data collected in the MRH study over the period 1934 to 1974 were considered to be accurate; there is, however, the possibility of coding, keypunching and reporting errors. Since many of the women interviewed had been enrolled in the MRH study during only part of their entire reproductive life, accuracy in recall could only be checked for the time when a woman was participating. In the MRH protocol a woman who failed to record any event when it occurred was instructed not to make the entry from memory. For each year she menstruated, a woman was asked in the interview to recall her typical menstrual cycle length in days and the number of menstrual cycles shorter and longer than usual. For this investigation an "extremely short" cycle was defined as less than 21 days; a cycle greater than 42 days was considered "extremely long." To estimate cycle variabil-
ity, each woman was asked to categorize her menstrual cycle patterns for each year in one of three ways: 1) regular, give or take two days; 2) somewhat irregular but rarely more than one week, and 3) totally variable and unpredictable. The mean menstrual cycle lengths for the age periods less than 20, 20-29, 30-39, 40-49 and 50-59 years were calculated from the data collected on the questionnaire and contrasted with the MRH data. If the difference of the two means for a particular age period was within specified limits, it was considered to be a match. The measure used in analysis was the per cent agreement, which is the number of matches over the number of possible matches times 100. A precise estimate of standard deviation of menstrual cycle variability was computed from the MRH data and then classified into one of the groupings used on the questionnaire. Summary values for the interview data and for the MRH data were determined for each age group so the per cent agreement could be studied. For the variables extremely long or extremely short cycles, the percentage of women having such cycles who failed to report them in the interview was used. RESULTS
Age of menarche. Table 1 presents the difference in years between the TABLE 1
Accuracy of recalled age for menarche Difference* in years
No.
-4 -3 -2 -1 0 1 2 3
1 0 6 27 94 24 7 1
1 0 4 16 59 15 4 1
160
100
Total
%
' The difference is recalled age minus actual age.
VARIATIONS IN THE REPORTING OF MENSTRUAL HISTORIES
menarcheal age reported in the interview and that recorded in the MRH. The length of recall (i.e., time between occurrence of event and recall of the event on interview) ranged from 17 years to 53 years with a mean of 33.9 years. Fifty-nine per cent of the women accurately reported age at menarche; 90 per cent were within one year. The mean age at menarche as recalled was 12.67 ± 0.11 while the mean age at menarche on enrollment was 12.68 ± 0.09. Age at natural or surgical menopause. Sixty-eight of the women had reached menopause by 1974 including 18 who had had a hysterectomy. The average length of recall was 7.6 years for women who had natural menopause and 10.6 years for TABLE 2
Accuracy of recalled age for menopause Difference* in years
No.
%
-5 -4 -3 -2 -1 0 1 2 3 4 5 6
1 1 0 1 2 22 13 4 2 0 2 1
2.0 2.0 0.0 2.0 4.1
44.9 26.5
Total
49
100.0
8.2 41 0.0 41 20
* The difference is recalled age minus actual age. TABLE 3
Accuracy of recalled age for hysterectomy Difference* in years
No.
%
-1 0 1 2
2 10 3 3
11.1 55.6 16.7 16.7
Total
18
100.0
* The difference is the recalled age minus the actual age.
183
those who had surgical menopause. Tables 2 and 3 display the distributions of the differences between the two ages. Twenty-two of the 49 women accurately recalled their menopausal age; an additional 15 were correct within one year. Ten of 18 correctly gave their age at the time of their hysterectomy and an additional five were correct within a year. The mean recalled age for menopause was 0.6 years older than the mean actual age; for hysterectomy 0.4 years older. Menstrual cycle length. Of interest was the relationship between accuracy of recall and length of recall. The sample was divided into two cohorts, age 44 or younger at time of interview and age 45 and older. The length of recall was examined by determining the accuracy of recall for various age groupings of a woman's reproductive life. The groupings used were: 1) age 42 days; a short cycle is
AMIEJCAN JOURNAL or EPIDEMIOLOGY
Copyright © 1979 by The Johns Hopkins University School of Hygiene and Public Health All rights reserved
Printed in USA.
VARIATIONS IN THE REPORTING OF MENSTRUAL HISTORIES JUDY A. BEAN,' JAMES D. LEEPER,' ROBERT B. WALLACE,1 BARRY M. SHERMAN3 AND HELEN JAGGER4 Bean, J. A. (Oept. of Preventive Medicine and Environmental Health, U. of Iowa, Iowa City, Iowa 52242), J. D. Leeper, R. B. Wallace, B. M. Sherman and H. Jagger. Variations In the reporting of menstrual histories. 4m J Epidemiol 109:181-185, 1979. This investigation examined the accuracy of recall of females to questions concerning ages at menarche, natural and surgical menopause, first use of oral contraceptives and mean menstrual cycle length and variance. A sample of 160 women who had recorded their menstrual and reproductive events as they occurred were administered a questionnaire concerning these events, with responses compared to the original data. For the variables age at menarche, age at natural menopause, age at surgical menopause and age at first use of oral contraceptives, the percentage of women who correctly recalled within a year ranged from 75% to 90%. Recollection of menstrual cycle length and variability by Interview was considered unreliable. These findings are encouraging regarding the ability to recall the age when certain menstrual and reproductive events occur, but not for menstrual cycle intervals or patterns. Because these women were well-educated and had once recorded study variables, these results might be considered optimal. menopause; menstruation; questionnaires; recall
Information regarding menarche, menstrual cycle patterns, menopause, oral contraceptive use and other menstrual and reproductive events collected by interview are of special interest in the study of fertility, population biology, family planning and breast cancer risk. Extensive evidence indicates that inaccuracies may occur in the recall of information, related to the nature of the question, length of recall, interview setting and other interview variables (1). In the present investigation, which was deReceived for publication March 6, 1978, and in final form July 25, 1978. 1 Department of Preventive Medicine and Environmental Health, University of Iowa, Iowa City, IA 52242 (address for reprint requests). 1 College of Community Health Sciences, University of Alabama, Tuscaloosa, AL. 1 Department of Internal Medicine, University of Iowa, Iowa City, IA. 4 Minnesota Health Department, Minneapolis, MN. This study was supported by grant #CA15104-02 from the National Cancer Institute.
signed to validate a questionnaire used in a case-control study of menstrual and reproductive antecedents of breast cancer, the accuracy of recall response of such variables was tested by comparing responses to a prospectively collected data set. METHODS
In 1934, Dr. Alan Treloar began the Menstrual and Reproductive History study (the MRH) by enrolling coeds at the University of Minnesota who agreed to record the dates of onset and cessation of menstrual flow, pregnancies, lactation, contraceptive use and related events (2). Over 500 persons reported their menstrual histories the first year, and 2000 more were added before the original panel was closed in 1938. From then until the present, data on menses of this original panel have been gathered continuously. In the 1940's a new panel was ini-
181
182
BEAN, LEEPER, WALLACE, SHERMAN AND JAGGER
tiated, and another one was started in the early 1960's, so that by 1970, 3780 women had participated in this study. In the protocol, a woman remains in the study as long as she wishes, or until she is lost through failure of mail contact or until menses ceases. Women living in the Minneapolis-St. Paul metropolitan area who had participated in the MRH study for at least five years were identified. The 425 women meeting these criteria were classified by age into three groups: 25-34, 35-44, and 45-64 years. Forty women were randomly selected in each of the first two age groups and 80 in the last. No woman refused the interview. The interview consisted of a structured questionnaire administered by a trained interviewer who collected information on demographic variables, year of menarche, year of menopause (when applicable), menstrual cycle length and variability, number of cycles over 42 days and less than 21 days, age at hysterectomy, age at onset of oral contraceptive use, number of pregnancies and other events. The data collected in the MRH study over the period 1934 to 1974 were considered to be accurate; there is, however, the possibility of coding, keypunching and reporting errors. Since many of the women interviewed had been enrolled in the MRH study during only part of their entire reproductive life, accuracy in recall could only be checked for the time when a woman was participating. In the MRH protocol a woman who failed to record any event when it occurred was instructed not to make the entry from memory. For each year she menstruated, a woman was asked in the interview to recall her typical menstrual cycle length in days and the number of menstrual cycles shorter and longer than usual. For this investigation an "extremely short" cycle was defined as less than 21 days; a cycle greater than 42 days was considered "extremely long." To estimate cycle variabil-
ity, each woman was asked to categorize her menstrual cycle patterns for each year in one of three ways: 1) regular, give or take two days; 2) somewhat irregular but rarely more than one week, and 3) totally variable and unpredictable. The mean menstrual cycle lengths for the age periods less than 20, 20-29, 30-39, 40-49 and 50-59 years were calculated from the data collected on the questionnaire and contrasted with the MRH data. If the difference of the two means for a particular age period was within specified limits, it was considered to be a match. The measure used in analysis was the per cent agreement, which is the number of matches over the number of possible matches times 100. A precise estimate of standard deviation of menstrual cycle variability was computed from the MRH data and then classified into one of the groupings used on the questionnaire. Summary values for the interview data and for the MRH data were determined for each age group so the per cent agreement could be studied. For the variables extremely long or extremely short cycles, the percentage of women having such cycles who failed to report them in the interview was used. RESULTS
Age of menarche. Table 1 presents the difference in years between the TABLE 1
Accuracy of recalled age for menarche Difference* in years
No.
-4 -3 -2 -1 0 1 2 3
1 0 6 27 94 24 7 1
1 0 4 16 59 15 4 1
160
100
Total
%
' The difference is recalled age minus actual age.
VARIATIONS IN THE REPORTING OF MENSTRUAL HISTORIES
menarcheal age reported in the interview and that recorded in the MRH. The length of recall (i.e., time between occurrence of event and recall of the event on interview) ranged from 17 years to 53 years with a mean of 33.9 years. Fifty-nine per cent of the women accurately reported age at menarche; 90 per cent were within one year. The mean age at menarche as recalled was 12.67 ± 0.11 while the mean age at menarche on enrollment was 12.68 ± 0.09. Age at natural or surgical menopause. Sixty-eight of the women had reached menopause by 1974 including 18 who had had a hysterectomy. The average length of recall was 7.6 years for women who had natural menopause and 10.6 years for TABLE 2
Accuracy of recalled age for menopause Difference* in years
No.
%
-5 -4 -3 -2 -1 0 1 2 3 4 5 6
1 1 0 1 2 22 13 4 2 0 2 1
2.0 2.0 0.0 2.0 4.1
44.9 26.5
Total
49
100.0
8.2 41 0.0 41 20
* The difference is recalled age minus actual age. TABLE 3
Accuracy of recalled age for hysterectomy Difference* in years
No.
%
-1 0 1 2
2 10 3 3
11.1 55.6 16.7 16.7
Total
18
100.0
* The difference is the recalled age minus the actual age.
183
those who had surgical menopause. Tables 2 and 3 display the distributions of the differences between the two ages. Twenty-two of the 49 women accurately recalled their menopausal age; an additional 15 were correct within one year. Ten of 18 correctly gave their age at the time of their hysterectomy and an additional five were correct within a year. The mean recalled age for menopause was 0.6 years older than the mean actual age; for hysterectomy 0.4 years older. Menstrual cycle length. Of interest was the relationship between accuracy of recall and length of recall. The sample was divided into two cohorts, age 44 or younger at time of interview and age 45 and older. The length of recall was examined by determining the accuracy of recall for various age groupings of a woman's reproductive life. The groupings used were: 1) age 42 days; a short cycle is
