Contribution of Occupational Physical Activity Toward Meeting Recommended Physical Activity Guidelines --- United States, 2007

Regular physical activity helps maintain healthy weight and reduces the likelihood of developing chronic diseases. The 2008 Physical Activity Guidelines for Americans (1) are derived from the most recent scientific review of physical activity health benefits and do not differentiate among physical activity for leisure, transportation, work, or other purposes. To examine the potential influence of occupational physical activity on meeting minimum weekly aerobic physical activity guidelines, the Washington State Department of Health (WADOH) analyzed demographic patterns in physical activity levels with and without consideration of occupational physical activity using 2007 Behavioral Risk Factor Surveillance System (BRFSS) data. This report describes the results of that analysis, which indicated that, approximately two thirds (64.3%) of U.S. adults met minimum physical activity guidelines through nonoccupational physical activity. When occupational physical activity (defined as reported work activity of mostly walking or heavy labor) was considered, an additional 6.5% of adults likely met the guidelines. The increase was greatest for Hispanic men (14.4%) and men with less than a high school education (15.9%). Public health agencies conducting surveillance of population physical activity levels also should consider including occupational physical activity, which will help to identify demographic groups for targeted programs that increase physical activity.

BRFSS is a state-based, random-digit--dialed telephone survey of the noninstitutionalized, U.S. civilian adult population. The Council of American Survey Research Organizations (CASRO) median response rate for the 2007 BRFSS survey was 50.6%. Among 430,912 respondents, complete occupational and nonoccupational physical activity data were available for 386,397 respondents from 50 states and the District of Columbia.

BRFSS collects data on frequency and duration of nonoccupational physical activity, which includes leisure, transportation (e.g., walking), and maintaining a home. WADOH computed the products of activity frequency (days per week) and duration (minutes per day) for moderate-intensity and vigorous-intensity activities. Consistent with the guidelines, WADOH classified respondents as having met guidelines if they reported weekly nonoccupational physical activity of ≥150 minutes of moderate-intensity activity (e.g., brisk walking or gardening), ≥75 minutes of vigorous-intensity activity (e.g., running or heavy yard work), or a combination of moderate-intensity and vigorous-intensity activity (with vigorous-intensity activity minutes multiplied by two) totaling ≥150 minutes.

BRFSS does not collect data on occupational physical activity frequency and duration; instead, respondents who indicate employment are asked whether their activity at work is mostly standing or sitting, mostly walking, or mostly heavy labor or physically demanding work.* For this analysis, respondents who did not meet guidelines through nonoccupational physical activity were coded as meeting the guidelines if they reported mostly walking or mostly heavy labor or physically demanding work (Figure).

WADOH computed age-adjusted prevalence of meeting physical activity guidelines by selected demographic characteristics and calculated age-adjusted prevalence ratios (PRs) for meeting guidelines by fitting two sets of Poisson regressions in which the outcome measures were meeting recommendations (in the first set through nonoccupational activity and in the second set through either nonoccupational or occupational activity). Each Poisson regression contained age and, except for the analysis in which age was the only predictor, an additional predictor variable: race/ethnicity, annual household income, or education. All analyses were stratified by sex and conducted using statistical software that accounted for the complex sampling design.

Approximately two thirds (68.5%) of men met guidelines through nonoccupational physical activity. When occupational physical activity levels also were considered, the proportion meeting guidelines increased from 68.5% to 76.3% (Table 1); 14.8% (95% confidence interval [CI] = 14.4%--15.3%) of men reported "mostly walking," and 14.3% (CI = 13.9%--14.7%) reported "mostly heavy labor" at work. For women, the proportion increased from 60.4% to 65.7% (Table 2); 12.7% (CI = 12.4%--13.0%) of women reported "mostly walking," and 3.4% (CI = 3.3%--3.6%) of women reported "mostly heavy labor" at work. Hispanic men and men with less than a high school education exhibited the greatest absolute gains in the proportion meeting guidelines when occupational physical activity was included (from 60.6% to 75.0% and from 55.7% to 71.6%, respectively). Among Hispanic men, 24.3% (CI = 22.6%--26.2%) reported "mostly walking," and 15.0% (CI = 13.5%--16.5%) reported "mostly heavy labor" at work; among men with less than a high school education 21.2% (CI = 19.4%--23.2%) reported "mostly walking," and 18.4% (CI = 16.8% -- 20.0%) reported "mostly heavy labor."

Hispanic men had a lower prevalence of meeting guidelines through nonoccupational physical activity compared with non-Hispanic white men (PR = 0.85) (Table 1). However, when occupational physical activity was included, the PR was attenuated (i.e., it approached 1.0; PR = 0.97). Similarly, men with less than a high school education had lower prevalence of meeting physical activity guidelines through nonoccupational physical activity compared with men with a college degree (PR = 0.75). When occupational physical activity was included, the PR was attenuated (PR = 0.93). Similar patterns in attenuation of PRs were noted when comparing men with reported annual household incomes of ≤$35,000 with those with reported annual household incomes of ≥$75,000. Among women, inclusion of occupational physical activity minimally changed the age-adjusted PRs for meeting physical activity guidelines by education, race/ethnicity, or annual household income categories (Table 2).

Reported by

Lillian Bensley, PhD, Juliet VanEenwyk, PhD, Office of Epidemiology, Washington State Dept of Health. Myduc Ta, PhD, EIS Officer, CDC. Corresponding contributor: Lillian Bensley, Washington State Dept of Health, 360-236-4248, lillian.bensley@doh.wa.gov.

Editorial Note

As expected, findings from this report provide evidence for a modest contribution of occupational physical activity toward successfully meeting minimum physical activity guidelines among U.S. adults, with a larger impact for some subpopulations than others. National Health Interview Survey (NHIS) data from 1990 and earlier revealed that approximately half of respondents classified as sedentary in leisure time reported ≥1 hour of strenuous occupational activity daily; that report indicated that assessing only leisure activity might underestimate physical activity (2). Recent analyses from NHIS are not available because questions regarding the amount of job-related physical activity have not been asked since 1990. The findings presented in this report are consistent with reports of Hispanic persons expending more energy at work than persons of other racial/ethnic groups (3). In addition, education and income are strong predictors of leisure-time physical activity, and they remain important predictors of total activity, even though including occupational activity attenuates the association between education and physical activity for men.

Although the BRFSS occupational physical activity question has been reported as valid and reliable for classifying physical activities at work (4--6), the question does not quantify the intensity or duration of continuous occupational physical activity. For this report, the analysis assumed that "mostly walking" included moderate-intensity activity in ≥10-minute intervals for ≥150 minutes per week and "mostly heavy labor" included vigorous-intensity activity in ≥10-minute intervals for ≥75 minutes per week. If the actual time spent in activity of sufficient intensity is less than this, then the effect of occupational physical activity on meeting the minimum aerobic activity guidelines will be overestimated. Relative to a standard work week of 40 hours, these assumptions seem reasonable. Also, a variety of occupational walking activities are in the "moderate" range, and a variety of heavy labor activities are in the "vigorous" range, based on comparisons of energy need while performing a task to energy need at rest (5,7). However, a more detailed assessment of occupational physical activities would be needed to confirm these assumptions.

The findings in this report are subject to at least three limitations. First, because the duration of "mostly" walking or heavy physical labor is unavailable, it was not possible to assess whether respondents who did not meet guidelines through nonoccupational activity alone might meet guidelines through the combination of occupational and nonoccupational physical activity. As such, the proportions of persons meeting guidelines might have been underestimated. Second, BRFSS excludes persons in households without landline telephones. Finally, the 2007 BRFSS survey had a low CASRO response rate. These latter two factors can lead to bias, especially if physical activity patterns differ between those with and without landline telephones and between respondents and nonrespondents. The directions of these potential biases are unknown.

As one of the 10 leading health indicators in the United States (8), physical activity is monitored at state and national levels to provide information for public health program planning, implementation, and evaluation. The state of Washington has used combined occupational and nonoccupational physical activity data as part of its assessment to target communities for policy and environmental changes. Debate about the health benefits of physical activity at work is ongoing, but the current guidelines do not distinguish between occupational and nonoccupational physical activity. Thus, public health surveillance that includes both occupational and nonoccupational physical activity more accurately describes whether persons meet guidelines than surveillance that includes only nonoccupational physical activity. Because demographic groups vary in amounts of physical activity at work (9), surveillance that includes both occupational and nonoccupational physical activity can be used to target groups that could derive health benefits by being more physically active.

Acknowledgments

State BRFSS coordinators. Eric M. Ossiander, PhD, Office of Epidemiology, Washington State Dept of Health. Fleetwood Loustalot, PhD, Div for Heart Disease and Stroke Prevention, National Center for Chronic Disease Prevention and Health Promotion, Sheryl B. Lyss, MD, Betsy L. Cadwell, MSPH, Div of Applied Sciences, Scientific Education and Professional Development Program Office, CDC.

References

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