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American Journal of Epidemiology Advance Access originally published online on March 10, 2007
American Journal of Epidemiology 2007 165(10):1124-1133; doi:10.1093/aje/kwk119
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American Journal of Epidemiology Copyright © 2007 by the Johns Hopkins Bloomberg School of Public Health All rights reserved; printed in U.S.A.

PRACTICE OF EPIDEMIOLOGY

Reproducibility and Validity of the Shanghai Men's Health Study Physical Activity Questionnaire

Adriana L. Jurj1, Wanqing Wen1, Yong-Bing Xiang2, Charles E. Matthews1, Dake Liu2, Wei Zheng1 and Xiao-Ou Shu1

1 Department of Medicine, Vanderbilt Epidemiology Center, Vanderbilt University Medical Center and Vanderbilt-Ingram Cancer Center, Nashville, TN
2 Department of Epidemiology, Shanghai Cancer Institute, Shanghai, People's Republic of China

Correspondence to Dr. Xiao-Ou Shu, Center for Health Services Research, Vanderbilt University Medical Center, 1215 21st Avenue South, Nashville, TN 37232-8300 (e-mail: xiao-ou.shu{at}vanderbilt.edu).

Received for publication July 5, 2006. Accepted for publication October 31, 2006.


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
Reproducibility and validity of the physical activity questionnaire (PAQ) used in the Shanghai Men's Health Study (2003–2006, People's Republic of China) was evaluated in a random sample of 196 participants aged 40–74 years. Participants completed a PAQ at baseline and again 1 year later, 12 monthly 7-day physical activity recalls, and four quarterly 1-week physical activity logs. Reproducibility was evaluated by using the two PAQs and validity by comparing the PAQs with 1-year averages of the two criterion measures: 7-day physical activity recall and physical activity log. The PAQ had moderate to high reproducibility for measuring adult exercise participation ({kappa} = 0.60) and energy expenditure (rs = 0.68), nonexercise activities (correlation coefficients = 0.42–0.68), and total daily energy expenditure (rs = 0.68, {kappa}quartiles = 0.47). Correlations between the PAQ and criterion measures of adult exercise were 0.45 (7-day physical activity recall) and 0.51 (physical activity log) for the first PAQ and 0.62 (7-day physical activity recall) and 0.71 (physical activity log) for the second PAQ. Correlations between PAQ nonexercise activities and the physical activity log and 7-day physical activity recall were 0.31–0.86. Correlations for total energy expenditure were high (0.62–0.77). Results indicate that the Shanghai Men's Health Study PAQ has reasonable reproducibility and validity for classifying men by their level of exercise and nonexercise activities in this cohort.

exercise; questionnaires; reproducibility of results; validation studies

Abbreviations: MET, metabolic equivalent task; PAQ, physical activity questionnaire; SMHS, Shanghai Men's Health Study


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
A large body of research indicates the health benefits of participation in physical activity (1). Reduced risk of several chronic diseases such as cardiovascular disease (2–6), type 2 diabetes mellitus (6–8), and certain cancers (9–14), as well as decreased risk of cardiovascular and overall mortality (15–20), have been associated with participation in physical activity, although the results have not been entirely consistent (21, 22). Therefore, accuracy of the measurement of physical activity, although it remains a challenging task, plays an essential role in evaluating the effects of physical activity. Likewise, studies showing that not only leisure-time activities but also other physical activities provide health benefits (5, 23) emphasize the importance of capturing the full range of activities occurring in various social domains, including leisure-time, transportation, household, and occupation.

Physical activity questionnaires (PAQs) are the most common method used to collect physical activity data in large observational studies. Because patterns of physical activity and accuracy of self-reports may differ across cultural/ethnic backgrounds (24) or gender (25), it is necessary to validate the instrument in each study population in which it is used. The purpose of the present study was to evaluate the reproducibility and validity of the PAQ implemented in the baseline survey of the Shanghai Men's Health Study (SMHS).


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 References
 
Study subjects and design
The SMHS is an ongoing, population-based, prospective cohort study of 61,582 men between the ages of 40 and 74 years that was designed to investigate the effects of various behavioral factors, including physical activity, on the risk of cancer and other chronic diseases. Recruitment for the SMHS was initiated in April 2002 and was completed in June 2006. Participants, residents of seven communities of urban Shanghai, People's Republic of China, were invited to take part in the study by trained interviewers through in-person contact. A total of 61,582 participants were enrolled in the study, with a response rate of 74.1 percent. Reasons for nonparticipation included refusal (21.1 percent); out of the area during enrollment (3.1 percent); and other miscellaneous reasons, including poor health or hearing problems (1.7 percent).

Potential participants in the current validation study were randomly selected from the SMHS rosters of participants living in two of the eight communities. These two study communities were chosen primarily for practical reasons, that is, based on proximity to the interviewers' residence. Fifteen study interviewers conducted the participant recruitment and subsequent face-to-face interviews. Approximately 17 primary and 68 alternate cohort members were identified for possible recruitment for each interviewer, who then followed the study subjects throughout the 1-year study period. Between April 2003 and May 2004, 214 participants were recruited into this validation study, and 69.3 percent were primary contacts. The study was approved by the institutional review boards of all participating institutions, and all participants signed a written consent.

At baseline, an in-person interview was conducted with participants to collect information on sociodemographic characteristics (education, occupation, income), personal habits (smoking, alcohol consumption), occupational history, disease history and medication use, dietary habits, and physical activity. Dietary data were collected by using a food frequency questionnaire that inquired about the frequency and amount of specific foods eaten. The amount in grams per day of food consumed was derived, and total dietary energy and nutrient intakes were calculated by using the Chinese Food Composition Tables (26). At the end of the interview, interviewers measured participants' weight and height by using a standard protocol.

Physical activity data were collected through the PAQ, administered as part of the baseline survey. Validation instruments were administered during the following 1-year period, including 12 (monthly) 7-day physical activity recalls and four (quarterly) 1-week physical activity logs initiated 3 months after the first 7-day physical activity recall (figure 1). The PAQ was readministered at the end of the validation study, approximately 1 year (median: 1.2, range: 0.9–2.1 years) after baseline administration. Of the 214 participants who completed the first PAQ, 196 (91.6 percent) completed the second PAQ and were included in the analyses. All of these subjects provided at least nine 7-day physical activity recalls, and 97.5 percent completed all 12 recall interviews. All participants but one (who completed only three physical activity logs) completed all four physical activity logs.


Figure 1
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  		FIGURE 1. Timing of physical activity measures in the Shanghai Men's Health Study (SMHS)–Validation Study, People's Republic of China, 2003–2005. Dates show when each instrument was initially administered. PAQ, physical activity questionnaire.

 
The SMHS PAQ
The questionnaire was based on the PAQ used in the Shanghai Women's Health Study, which has been validated previously (27). The PAQ is available from the authors upon request. Briefly, the SMHS PAQ evaluated regular exercise/sports participation (i.e., at least once a week for at least 3 months in a year) in adulthood (in the past 5 years) and adolescence (at ages 13–15 years). Information collected about adolescent exercise activities included length of participation (years), weekly duration (hours/week), and participation on athletic teams (yes/no). Adult exercise was assessed in terms of type, duration (hours/week), and years of participation for up to three types of exercise/sports activities. Information regarding nonoccupational, nonexercise activities such as stair climbing (flights of stairs/day), walking and cycling to/from work and related to other responsibilities (minutes/day), and housework (hours/day) during the past year was also assessed.

Seven-day physical activity recall
The 7-day physical activity recall instrument was structured and worded similarly to the one evaluating nonoccupational activities on the SMHS PAQ. Although the PAQ asked for information about activity patterns in the past 1–5 years, the 7-day physical activity recall asked for this information for the week before the interview. Information was collected regarding as many as three exercise activities (i.e., type and duration). The amount of time spent walking, cycling, and doing housework was assessed, as was the number of flights of stairs climbed each day. This questionnaire was administered monthly with in-person interviews.

Physical activity log
The physical activity log was adapted for this study population from the physical activity log used to validate the PAQ used in the Shanghai Women's Health Study (27). For 7 consecutive days, at the end of each assessment day, participants were instructed to record the amount of time they spent engaged in specific categories of activity listed in their logs. The activity categories included sleeping; sitting; stair climbing; walking and cycling for transportation; engaging in several household activities; performing light, moderate, and vigorous occupational activities; and participating in up to four different sports or exercises.

Data collected through each of the physical activity instruments were summarized in a similar manner in terms of duration and energy expenditure (metabolic equivalent task (MET)-hours), by activity domain (e.g., exercise/sports, walking and cycling to/from work and for daily errands, housework) and overall. Energy expenditure was calculated by multiplying the time (in hours) spent in each activity by the corresponding MET value obtained from the Compendium of Physical Activities (28). Total daily nonoccupational energy expenditure was calculated as the sum of energy expenditure in exercise/sports and nonexercise activities. On the basis of the MET values assigned to each activity, intensity of exercise/sports was categorized as light (1.5–2.9 METs), moderate (3.0–6.0 METs), or vigorous (≥6.1 METs).

Statistical analyses
Prevalence (percentage reporting) and descriptive statistics for men reporting participation were calculated. Nonparametric statistical tests were used because of the skewed distributions of the physical activity summary variables.

Reproducibility was determined by test-retest analyses using data from the two administrations of the SMHS PAQ. Exercise energy expenditure and total energy expenditure were examined as continuous as well as categorical (quartile) variables. Spearman's rank-order correlations (rs) were calculated to evaluate the reproducibility of continuous physical activity summary variables. Categorical variables were examined by using cross-tabulation of activity reports to obtain the proportion of men reporting the same category consistently ("correct classification") as well as extreme reporting variation between administrations. Extreme variation in reporting reflects the largest possible change in reported participation between PAQ administrations. The kappa statistic ({kappa}) was used to evaluate the reproducibility of classification for categorical variables.

Validity of the SMHS PAQ was assessed by comparing PAQ data with the 1-year averages of the criterion measures (7-day physical activity recall and physical activity log). To assess the measurement properties of our criterion measures, we also evaluated correlations between the 1-year averages of the 7-day physical activity recalls and the physical activity logs. Spearman's rank-order correlations were calculated between the corresponding physical activity summary measures derived from both PAQ administrations and the two criterion measures. Medians of total nonoccupational activity and daily energy expenditure were compared by using the Wilcoxon signed rank test.

Statistical analyses were performed by using SAS version 9.1 for Windows software (SAS Institute, Inc., Cary, North Carolina). p values of less than 0.05 were considered statistically significant.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 References
 
The average age of the 196 participants was 55.2 years (standard deviation, 9.6), more than half had completed at least high school, and 61 percent were current smokers (table 1). In terms of occupation in the longest-held job, 27 percent were professionals, 19 percent had clerical jobs, and more than 50 percent were manual workers/farmers. Almost half of study participants reported a monthly per capita income of 1,000 yuan (US $121.90) or higher, 43 percent reported 500–999 yuan (US $61.00–121.80), and 10 percent reported less than 500 yuan (US $61.00). As presented in table 1, there were no statistically significant differences in the distribution of demographic and behavioral characteristics between the validation study participants and the "parent" SMHS cohort (p > 0.05).


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  		TABLE 1. Comparison of participants in the validation study with all cohort members, Shanghai Men's Health Study, People's Republic of China, 2003–2005

 
Descriptive statistics for the first and second administrations of the SMHS PAQ, as well as reproducibility results, are presented in table 2. At baseline, approximately 40 percent of men reported regular exercise participation in the past 5 years, and 94 percent reported exercising during adolescence. Among the exercisers, more than 70 percent reported participation in only one type of adulthood exercise/sports, and the vast majority reported participation in traditional Chinese exercises of moderate intensity (47 percent) or walking (40 percent) (data not shown in the tables). The prevalence of exercise/sports reported in the second PAQ was lower (36 percent), and median exercise duration and energy expenditure among participants reporting exercise were higher as compared with baseline, but these differences were not statistically significant. The {kappa} value of 0.60 indicates reasonable reporting consistency, and the Spearman's rank-order correlation coefficients for duration and energy expenditure were reasonably high (0.65 and 0.68, respectively) (table 2). Adolescent exercise participation (yes/no) was reported consistently over time ("correct classification" = 0.92) but with relatively low reproducibility of the duration of exercise (rs = 0.34). Number of flights of stairs climbed daily and time reported in daily cycling were significantly greater on the first PAQ administration (table 2). Reproducibility of daily walking was lowest among activities assessed (rs = 0.35), but the correlation coefficients for the other nonexercise activities were between 0.42 and 0.68 (table 2). The median energy expenditures calculated from all nonoccupational activities reported in the baseline and second PAQs were 8.7 MET-hours/day and 8.0 MET-hours/day, respectively, with a reasonable reproducibility (rs = 0.65, {kappa}quartiles = 0.47) (table 2).


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  		TABLE 2. Physical activity levels reported on the baseline (first) and retest (second) administrations of the Shanghai Men's Health Study PAQ{dagger} and reproducibility results, Shanghai Men's Health Study PAQ Validation Study, People's Republic of China, 2003–2005

 
Descriptive results for the 7-day physical activity recall and physical activity log are summarized in table 3. Nearly 65 percent and 59 percent of men reported participation in exercise/sports, predominantly of moderate intensity, on at least one 7-day physical activity recall and one physical activity log, respectively. When exercise reports on three of twelve 7-day physical activity recall administrations were used as an indicator of "regular exercise," only 46 percent of participants met this criterion (data not shown in the tables). Among other nonexercise lifestyle activities, walking for daily errands (>96 percent), housework (>95 percent), and stair climbing (>91 percent) were the most prevalent activities reported, and approximately 65 percent reported active transportation to work (table 3).


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  		TABLE 3. Physical activity levels (1-year averages) reported on the 7-day physical activity recall and physical activity log, Shanghai Men's Health Study PAQ* Validation Study, People's Republic of China, 2003–2005

 
Our evaluation of the measurement properties of the 7-day physical activity recall and physical activity log revealed moderate to strong rank-order correlations between these instruments for most activity domains: adult exercise (rs = 0.73), walking and cycling to/from work (rs = 0.54 and rs = 0.83, respectively), daily errands (rs = 0.40 and rs = 0.68, respectively), and housework (rs = 0.84) (table 3).

In terms of the validity of the SMHS PAQ relative to the criterion measures, moderate to strong rank-order correlations (rs: 0.44–0.71) were noted for adult exercise duration and energy expenditure, with the correlations being higher for the physical activity log comparisons and for the second administration of the PAQ (table 4). Correlations of moderate to high strength were also noted for most of the lifestyle activities (e.g., rs: 0.48–0.86), with the correlations being stronger for the 7-day physical activity recall and again for the second SMHS PAQ administration (table 4). High correlations were noted for total nonoccupational daily energy expenditure (7-day physical activity recall rs = 0.77, physical activity log rs = 0.73) and the second PAQ. Total daily nonoccupational energy expenditure was underestimated in the first and second PAQ in comparison to the physical activity log (median differences: –1 and –1.1 MET-hours/day, respectively), but the PAQ medians did not show a statistically significant difference from the 7-day physical activity recall (median differences: 0.1 and –0.1 MET-hours/day, respectively) (data not shown in the tables).


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  		TABLE 4. Spearman's correlations between the Shanghai Men's Health Study PAQ* and the 7-day physical activity recall and physical activity log for all activities, Shanghai Men's Health Study PAQ Validation Study, People's Republic of China, 2003–2005

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
References
 
In this validation study, we found that the SMHS PAQ provided reproducible and valid results. Therefore, it will enable the reasonable classification of men in the cohort into high and low activity categories for both exercise and sports participation and highly prevalent nonexercise activities, such as stair climbing, active transportation, and housework.

A similar questionnaire was validated by using a similar design over a 2-year period in a sample of women from the Shanghai Women's Health Study and was found to have reasonable reproducibility and validity, especially for exercise/sports (test-retest: {kappa} = 0.64, intraclass correlation coefficients = 0.70, comparison to 7-day physical activity recall and physical activity log: rs = 0.50–0.80) (27). However, for nonexercise lifestyle activities, the reproducibility and validity values for women were slightly lower than those reported here for men. This finding is consistent with previous reports that have shown better overall performance of similar physical activity instruments for men (25, 29). However, the finding may also be explained by gender differences in the prevalence and patterns of physical activity and the longer duration of time (2 years) during which the validation study was conducted among women (27).

Previous validation studies comparing PAQs with physical activity records have revealed correlation coefficients ranging from 0.24 to 0.73 for exercise (30–34), whereas validity coefficients for household and transportation/daily walking, when specifically evaluated, tended to be lower (34). Validity coefficients reported in this study are similar to, if not higher than, those reported from validation studies of other PAQs previously demonstrated to have utility in prospective epidemiologic research (35–38). For example, Friedenreich et al. (29) recently reported validity coefficients of 0.42 for men and women combined and 0.46 for men using criterion measures similar to those used in this study. The reasons for this difference are not immediately clear, particularly given the similarities of the criterion measures used in both studies. We speculate that there may be greater heterogeneity in the activity levels among adults in our study population as a consequence of their living in a dense, urban environment that demands participation in active transportation to get to and from work and to complete household and personal errands. Greater variability in activity levels in our study population may have contributed to the magnitude of the validity coefficients we observed relative to those in other studies.

The validity coefficients for the activity logs were higher than those for the 7-day questionnaire for adult exercise. However, for the nonexercise activities, the coefficients were higher for the 7-day physical activity recall compared with the physical activity log, perhaps because of the greater similarities in question structure and content between the 7-day and cohort questionnaires. Furthermore, the correlations in analyses of the second SMHS PAQ were stronger compared with the first PAQ administration, likely in relation to better temporal sequencing with the criterion measures and/or enhanced reporting accuracy following completion of the intensive measurement protocol during the study period. Nevertheless, even if no important changes in the prevalence of activities were noted between the first and second PAQ administrations, a slightly reduced prevalence of stair climbing and daily cycling, associated with a reduced number of flights of stairs climbed and time spent in daily cycling, was noted. These changes may reflect an enhanced understanding of the types of activities being evaluated by the investigators (i.e., learning effect). Therefore, probably the best estimate of the validity of the SMHS PAQ lies between the estimates provided in our evaluation of the first and second administrations of the PAQs (table 4).

Most previous reproducibility studies have been conducted over shorter periods of time (24, 25, 34, 39, 40). Eight- to 12-month reproducibility values for adult exercise behaviors from the College Alumnus (30) and the Minnesota Leisure Time (31) physical activity questionnaires have been in the range of 0.31–0.71, very close to results reported here (rs = 0.68). There are fewer comparative data in the literature for reproducibility of nonexercise activity domains as evaluated in our study (e.g., stair climbing, active transportation, housework). For various groupings of nonexercise activities, the correlation coefficients for 3- to 12-month retest analyses were between 0.30 and 0.71 in previous reports (29, 31, 39, 41). Except for transportation for daily errands, the reproducibility of the SMHS PAQ in assessing nonexercise activities in our study is in the higher end of this range.

Reproducibility coefficients have been noted to decrease in studies with test-retest intervals longer than 1 month (30, 31, 39). For example, Roeykens et al. (39) reported short-term (146 (standard deviation, 11 days)) reliability values for transportation, housework, and exercise energy expenditure of 0.57–0.92, whereas intraclass correlation coefficients for long-term (240 (standard deviation, 12 days)) reliability were 0.45–0.74 (World Health Organization Monitoring of Trends and Determinants in Cardiovascular Disease (WHO-MONICA) Optional Study of Physical Activity questionnaire). This reduction may reflect a combination of real changes in one's activity behavior over time (true intraindividual variation) and questionnaire reliability (reporting variation) that are probably becoming more obvious with longer gaps between test-retest questionnaire administrations. Therefore, the 1-year retest interval in this investigation likely resulted in a lower, thus more conservative, estimate of the reproducibility of the SMHS PAQ.

Adolescent exercise was reported by more than 93 percent of men in each PAQ, and 92 percent of the study sample reported participation in adolescent exercise at both PAQ administrations. Although no direct data were available to evaluate the validity of the adolescent exercise items on the SMHS PAQ, our previous finding for women, using similar questions about adolescent exercise, suggests that exercise early in life reduces breast cancer risk (11), which supports the potential utility of the adolescent exercise items.

The SMHS PAQ was designed to capture the full range of daily activities that are important contributors to the overall physical activity energy expenditure of Chinese adults living in a large urban area. For example, more than 50 percent of men reported walking or cycling to/from work, and more than 85 percent reported being involved in some form of housework, including food preparation and house cleaning. Likewise, the SMHS PAQ collected detailed information (i.e., type, frequency, duration) about each physical activity domain. In a study of women, Weller and Corey (42) demonstrated that failing to account for the full range of activities resulted in an underestimate of risk of all-cause and cardiovascular mortality by 20–40 percent.

Several limitations should be considered when interpreting the results of this study. First, as with all studies seeking to determine the validity of self-reported physical activity levels, few easily administered "gold standard" measures are available that can assess overall activity as well as the individual activity domains (e.g., exercise, household, transportation) that would enable a true validation of the instrument (43). The SMHS PAQ evaluated habitual physical activity patterns over relatively long time periods (5 years for exercise/sports and 1 year for nonexercise domains) and is subject to errors of recall attributable to memory (e.g., omission, intrusion) and long-term averaging (43–45). In contrast, our criterion measures minimized the potential for these types of recall errors because of their short recall periods and therefore may be considered to have conceptually different sources of error than the cohort questionnaire. Likewise, 7-day recalls and 1-week logs were completed during the 1-year time period recalled in the second PAQ for the nonexercise activities. We specifically selected these criterion measures for this reason and because they were also able to capture detailed information about specific types of activity assessed on the SMHS PAQ. Nevertheless, we recognize the limitations inherent in using self-reported criterion measures to evaluate the validity of the PAQ self-report, and this limitation of our study design should be considered when interpreting results from our study.

Several strengths of this study should also be considered. First, the study included cohort members randomly selected from the larger SMHS, and they were similar to the overall cohort in terms of demographic and behavioral characteristics. Second, the high rate of retention over the intensive 12-month measurement period and the high rate of completion of the 7-day physical activity recall and physical activity log by participants highlight the commitment of our participants to comply with study demands.

In conclusion, the present investigation suggests that the SMHS PAQ is a useful instrument for measuring exercise behaviors and other highly prevalent nonexercise activities in this cohort (e.g., transportation, housework). The instrument appears to be a good tool for stratifying SMHS participants into high and low activity levels for overall physical activity and by level of activity in specific activity domains.


   ACKNOWLEDGMENTS
 
This research was supported by grant RO1 CA82729 from the National Institutes of Health, Bethesda, Maryland.

The authors thank the research staff of the SMHS for their contribution to the study and Bethanie Hull for her technical assistance in preparing this manuscript.

Conflict of interest: none declared.


   References
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 

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