1 Department of Biostatistics and Epidemiology, School of Public Health and Health Sciences, University of Massachusetts, Amherst, MA.
2 Boston Biostatistics, Inc., Framingham, MA.
3 Department of Exercise Science, School of Public Health and Health Sciences, University of Massachusetts, Amherst, MA.
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ABSTRACT |
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epidemiologic methods; exercise; questionnaires; recall; reproducibility of results; women
Abbreviations: HLAQ, Historical Leisure Activity Questionnaire; MET, metabolic equivalent
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INTRODUCTION |
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To our knowledge, only two questionnaires have been developed to assess the duration, intensity, and frequency of lifetime physical activity (9, 10
). One fails to include information on household activity (10
). The omission of household activity, for women in particular, may underestimate activity and result in women being misclassified as sedentary when the opposite is true (11
). In addition, both questionnaires were designed to be interviewer administered, a technique often not practical for epidemiologic studies conducted among large numbers of participants.
The purpose of this study was to determine the reproducibility of the first self-administered lifetime physical activity questionnaire of which we are aware that was designed to assess the duration, frequency, and intensity of physical activity. This lifetime physical activity questionnaire, designed to measure household and recreational activity, was intended for use in a large prospective study of breast cancer among female college alumnae.
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MATERIALS AND METHODS |
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Subjects were recruited via a mailing from their respective alumnae association. To reach the intended sample size, the initial mailing was sent to 200 alumnae per college, stratified by geographic region of current residence, for a total of 400 letters. A total of 215 women (53.8 percent) met all of the eligibility requirements and completed a physical activity questionnaire (first measurement), which included an assessment of lifetime as well as current physical activity.
The 185 women who did not respond to the mail questionnaire did not differ significantly from respondents according to class (19551959, 19601964, 19651969, 19701974, or 19751980); however, more respondents (38.1 percent) than nonrespondents (26.9 percent) currently resided in non-Eastern regions (South, Midwest/Northwest, and Mountain/Pacific). Information on age, race, and parity was available from the alumnae association of one of the two colleges surveyed (51 percent of the sample), and for these subjects, respondents did not differ from nonrespondents.
For assessment of the reproducibility of the questionnaire, the physical activity questionnaire was repeated (second measurement) at the end of the subsequent year. For assessment of the validity of current physical activity, participants completed four 1-week activity logs corresponding to each season during the 1-year interval between questionnaire administrations (results presented elsewhere) (12). A total of 134 participants (62.3 percent) completed both questionnaires. The remaining 81 nonfinishers did not differ significantly from those who did complete the study with regard to physical activity measures.
Assessment of physical activity
We used a modified version of the Historical Leisure Activity Questionnaire (HLAQ) designed by Kriska et al. (13) to assess lifetime physical activity. The original version of the HLAQ was an interviewer-administered questionnaire designed to assess lifetime leisure activity among postmenopausal White women in relation to adult bone parameters. The HLAQ partitioned the life span into four prior age periods: ages 1421, 2234, 3550, and 50 or more years and inquired about leisure-time physical activities for each prior age period. We selected the HLAQ because the design was conducive to a self-administered format and it was originally developed for a population similar to our study.
We modified the HLAQ to be self-administered and also added household (housework and childcare) activities of moderate intensity and above (appendix figure 1). The earliest prior age period was modified to begin at "onset of menstruation." We also added two additional age periods: "ages 5165 years," to accommodate the age distribution of our study population and "past year" to assess current physical activity. Questions regarding occupational activities were added to the assessment of current physical activity.
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We calculated the average number of hours per week spent in each activity and multiplied it by its intensity, defined in multiples of the metabolic equivalent of sitting quietly (one metabolic equivalent (MET)), to arrive at a measure of average weekly energy expenditure attributable to each activity for that prior age period. One MET, for an adult of average weight, is approximately equal to an oxygen uptake of 3.5 ml/kg/min. The Compendium of Physical Activities (14) was used to assign METs for each activity. The average weekly expenditure attributable to each activity was summed to derive a total MET-hours/week approximation for each prior age period. Women who were less than age 51 years were not included in the total MET-hours/week for the age period 5165 years. A summary lifetime physical activity estimate was calculated as a weighted average of the four prior age periods, in which the weights were the number of years in each prior age period divided by the total number of lifetime years spanned by the questionnaire.
We developed several summary weekly activity scores to quantify the different levels of activity. Each activity was classified as moderate (3.05.9 METs) or vigorous (6.0 METs) intensity. Light-intensity activities were not included in summary measures because our ultimate goal was to assess the association between physical activity and breast cancer, which has been linked to activities of moderate intensity and above (6
). Activities were also classified by type: household and recreational. With this information, the average number of MET-hours/week for each level of intensity and type was calculated for each prior age period and for overall lifetime activity.
Analysis
Because the activity scores were skewed, we log-transformed the data for all correlation analyses. To evaluate the reproducibility of the questionnaire, we calculated intraclass correlation coefficients between the first and second measurements for overall lifetime activity as well as within each level of activity (intensity and type). The intraclass correlation coefficients were calculated based on a two-way mixed effect analysis of variance (15). This was repeated within each prior age period (menarche to 21 years and 2234, 3550, and 5165 years). A priori, we chose to examine the data both with and without walking because of the potential for exaggeration of self-reported estimations of walking (13
).
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RESULTS |
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We then stratified women according to age at entry into the study (<50 and 50 years) because women from different age cohorts may have different patterns of activity and abilities to recall activity (table 2). Younger women reported lower median values for total lifetime activity compared with older women (70.9 vs. 79.1 MET-hours/week, respectively, on the first measurement) as well as lower values for moderate-intensity activity and household activity. However, younger women reported higher median values for vigorous-intensity activity (15.5 vs. 10.9 MET-hours/week) compared with older women and similar values for recreational activity. As with the overall sample, both younger and older women reported slightly higher MET-hours/week on the first compared with the second measurement.
The reproducibility of total lifetime activity was assessed by calculating the correlation between the two questionnaire measurements of total lifetime activity and activity within each level of intensity (moderate and vigorous) and type (recreational and household) (table 3). Total lifetime activity was highly correlated overall (0.82) and ranged from 0.78 for household activity to a high of 0.87 for recreational activity. Because of the potential for exaggeration with estimations of walking, we recalculated the correlation coefficients after excluding self-reported walking from the summary measures of total, moderate-intensity, and recreational activity. Results were not substantively changed.
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We calculated summary estimates of activity for each prior age period (table 4). As reported on the first measurement, median total activity increased from 20.9 MET-hours/week in the earliest prior age period (age at menarche to 21 years) to a high of 71.5 and 81.2 MET-hours/week in the middle two prior age periods (2234 and 3550 years, respectively). This was followed by a decline to a median value of 50.1 MET-hours/week in the most recent prior age period (5165 years). Similar trends over time were observed for moderate-intensity activity as well as household activity. However, vigorous-intensity activity appeared to remain more stable over the prior age periods, fluctuating between a low of 6.4 MET-hours/week and a high of 9.3 MET-hours/week. Recreational activity increased slightly over time (16.0 MET-hours/week in the earliest prior age period to 24.0 MET-hours/week in the latest prior age period).
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The reproducibility of activity for each of the four prior periods was assessed by calculating the correlation between the two questionnaire measurements (table 5). Overall, correlations were higher for the more recent prior age periods. Total lifetime activity was highly correlated within each prior age period, ranging from a low of 0.70 for ages 2234 years to a high of 0.83 for ages 5165 years. Moderate-intensity activity was reasonably correlated for all prior age periods, with correlations ranging from a low of 0.62 in the earliest prior age period (age at menarche to 21 years) to 0.81 in the most recent prior age period (5165 years). Reproducibility scores for vigorous-intensity activity tended to be the highest values for each prior age period, followed closely by correlations for recreational activity, which were of similar magnitude. Correlations for household activity were lower, ranging from 0.54 for age at menarche to 21 years to a high of 0.72 in the age period 3550 years.
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DISCUSSION |
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This study has several limitations. The physical activity questionnaire asked women to average their activity over prior age periods ranging from 10 to 15 years in length. Therefore, we did not have information on variation in physical activity from year to year. Physical activity level in the earliest prior age period (age at menarche to 21 years) may be particularly variable, since this period includes both high school and college years (16). In general, however, values for reproducibility for this prior age period were similar to those for later, perhaps more homogenous, prior age periods.
The study sample was restricted to women who were of the same target age group (3965 years) as women in our ultimate study of physical activity and breast cancer. Hence, the results of this study may not be generalizable to men or to women who are not in the same age group. In addition, the participants in this study are college educated and may report levels of physical activity more accurately or be more active than the general population. However, this tool was intended for use in a college-educated population of women, and therefore, our findings for reproducibility would be relevant for epidemiologic studies among this population.
While other lifetime physical activity surveys have been published (9), we chose to use a modified version of the HLAQ (13
) because we felt that it was most readily adaptable to a self-administered format. Other tools have relied more heavily on interviewer administration. In particular, Friedenreich et al. (9
) have recently developed an interview-administered questionnaire designed to assess lifetime patterns of occupational, household, and exercise/sports activities. This tool requires subjects to specify their activities in an open-ended manner; particular activities are not delineated. In addition, unlike the HLAQ, the past is not divided into prior age periods. Instead, the interviewers use recall calendars and other memory cues to aid the participants in recalling their activities from their childhood to the current day.
While our modifications to the HLAQ included adding questions on occupational physical activity to the assessment of current physical activity, we did not add these questions to our assessment of lifetime physical activity. The original HLAQ was developed to characterize a lifetime of leisure physical activity in postmenopausal White women and did not include an assessment of lifetime occupational activity. Since our questionnaire was a modification of the original and was to be administered to a population of similar socioeconomic status, we chose not to add this dimension. Similarly, more recent surveys have not included occupational activity because of the decline in physical activity in most occupations (10). Few occupational tasks require energy output above the moderate level (17
), and because our ultimate goal was to assess the association between physical activity and breast cancer, we were interested only in activities of moderate intensity and above.
The use of cognitive methods such as memory aids is known to significantly improve recall accuracy (18). In modifying the HLAQ, we incorporated an extensive list of activities into the format of the questionnaire as a memory cue to help participants remember the activities that they performed in the past. However, the self-administered nature of our questionnaire precluded the use of other cognitive methods such as recall calendars. Durante and Ainsworth (18
), in a review of the cognitive model for the recall of physical activity, observed that using a calendar with landmark events makes a questionnaire much more difficult to administer and is less effective with a self-administered format. In particular, the absence of an interviewer to control the progression of the interview is an important impediment to focusing on the calendar and eliciting personal landmark events (18
).
The HLAQ used absolute intensities (MET levels) to score the activities reported on the questionnaire as opposed to relative intensities (e.g., relative to reported average maximal oxygen consumption or self-report of perceived exertion). For several reasons, we chose not to modify the questionnaire to utilize relative intensity measures. The questionnaire was to be self-administered, and we wished to avoid undue burden on the participants. In addition, the expert panel on "Measuring Physical Activity in Midlife, Older, and Minority Women," convened by the Women's Health InitiativeNational Institutes of Health/Centers for Disease Control and Prevention (19), has cautioned that the physical intensity of a task is often confused with the emotional demand of an activity. An interviewer, therefore, would be required to clarify this point effectively to participants. The expert panel concluded by recommending that future surveys use absolute measurements to make meaningful intersubject comparisons, while relative intensity measurements should be reserved to evaluate a person's functional capacity. Additionally, use of reported age-specific, maximal oxygen consumption adds an additional source of error, resulting in individual under- or overestimation of relative intensity.
While prior studies have not assessed the reproducibility of lifetime physical activity questionnaires that used a self-administered format, the reproducibility of two comparable, interviewer-administered lifetime questionnaires has been measured (9, 10
, 13
). Kriska et al. (13
) repeated the interviewer-administered HLAQ twice, 23 months apart, with 23 postmenopausal women and reported correlations ranging from 0.69 to 0.85 for kilocalories/week spent in recreational activity during four prior age periods. In a subsequent study among Pima Indians, lifetime occupational activity was added to the HLAQ in recognition of the fact that Native Americans still engage in physically demanding occupations such as farming. When administered 13 weeks apart to 18 participants aged 2136 years, the HLAQ had reproducibility coefficients of 0.94 for historical leisure and occupational activity combined (10
).
In the most recent study, Friedenriech et al. (9) repeated an interviewer-administered survey 68 weeks apart among 115 women aged 5075 years. Subjects were free of breast cancer, were predominantly Caucasian, and more than one third (34.8 percent) were college graduates. The questionnaire assessed lifetime patterns of occupational, household, and exercise/sports activities. Respondents were asked to self-report the intensity of each activity; moderate-intensity activities were defined as those that were not exhausting, that raised the heart rate slightly, and that caused some light perspiration; vigorous activities were those that increased the heart rate substantially and caused sweating. Correlations were 0.74 for total lifetime activity, 0.87 for occupational activity, 0.77 for household activity, and 0.72 for recreational activity. Similar to our findings, the authors observed higher correlations for lifetime vigorous-intensity activity (0.85) than for moderate-intensity activity (0.65).
We observed scores for reproducibility that were of similar magnitude to these prior questionnaires in spite of the fact that our questionnaire was self-administered and subjects had to recall further in the past. We did not find substantive differences in the reproducibility of recall by earlier versus more recent prior age period, although others have found accuracy of recall to decrease with increasing time since an event (20). Furthermore, prior studies used shorter intervals between administration of their lifetime physical activity questionnaires (3 months or less) (9
, 10
, 13
). Despite our longer interval (1 year), women were able to report lifetime physical activity reliably.
As in prior studies (9, 10
, 13
), we also observed that vigorous-intensity activity was more accurately recalled than moderate-intensity activity. These findings are in agreement with research that indicates that lower intensity activities are the most difficult to report (21
23
). We also observed higher correlations for recreational as opposed to household activities. Recreational activities may be more memorable since they may require planning or an effort that household activities do not. Recall of household activity appeared to be the least reproducible for household activity performed during the youngest age period. However, this type of activity may be more difficult to remember consistently because little time may have been spent in household activity during this prior age period.
We did not assess the validity of self-reported lifetime physical activity. This would have required a cohort of subjects who had self-reported their physical activity measures while they were of the ages corresponding to each prior age period. Even if available, it is unlikely that the physical activity assessment would have included the detailed activity levels reported in our questionnaire (i.e., type, intensity, frequency, and duration of activity) for each prior age period. Several studies, which have compared recalled activity with activity that was self-reported during a prior age period, have observed reasonable reliability among women, however. Falkner et al. (24) assessed recall of occupational and leisure-time activity reported 30 years previously among 71 female participants of the Buffalo Health Study. In addition to sports, leisure-time activity included several select lawn and garden activities. The authors observed correlations of 0.44 for occupational activity and 0.40 for leisure-time activity. Correlations ranged from 0.47 for moderate (35 METs) to 0.36 for vigorous (>5 METs) occupational activity and from 0.32 to 0.38 for moderate to vigorous leisure-time activity. Blair et al. (21
) examined recall of physical activity reported 10 years previously among 322 middle-aged women and found that reproducibility was higher for vigorous-intensity activities (0.41) than for moderate-intensity activities (0.25). Length of interval and age did not contribute significantly to variation in recalled activity. Finally, Lee et al. (25
) observed correlations of 0.33 between leisure-time physical activities reported 10 years earlier and recalled activities among 495 women aged 3559 years; however, the intensity of activity was not assessed.
In summary, we found this self-administered lifetime physical activity questionnaire to be highly reproducible. The questionnaire combines information on intensity, duration, and frequency of household and recreational activity into one measure and, unlike other questionnaires, need not be interviewer administered. Thus, this instrument can be considered reproducible and a potential tool for assessing lifetime physical activity patterns in etiologic studies of chronic diseases.
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ACKNOWLEDGMENTS |
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The authors thank Dr. Elaine Puleo for advice on statistical analysis, Maureen Vickers-Lahti for study coordination and statistical programming, and Tracy LaPorte and Jijun Lui for data management.
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NOTES |
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REFERENCES |
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