Effects of Leisure and Non-Leisure Physical Activity on Mortality in U.S. Adults over Two Decades

Purpose

To estimate the effects of the components of total physical activity, leisure-time and non-leisure activity, on all-cause mortality over two decades in a large, nationally representative sample of U.S. adults.

Methods

We used the first National Health and Nutrition Examination Survey (NHANES I, 1971–1975) and its Epidemiologic Followup Study (NHEFS), which tracked deaths of NHANES I participants through 1992. Using multivariable Cox regression, and multiple imputation for missing values of control variables, we related baseline leisure-time and non-leisure physical activity to all-cause mortality during follow-up, controlling for other risk factors. Adults 35 through 59 years of age (N = 5884) and 60 through 74 years of age (N = 4590) were analyzed separately.

Results

For persons aged 35–59, moderate non-leisure activity at baseline significantly reduced mortality risk over the next two decades by about 26%, high non-leisure activity by about 37%, compared with low non-leisure activity. For persons 60–74, risk reductions were 34% and 38%, respectively. Leisure-time activity was associated with lower mortality, but was not consistently significant when both types of activity were entered in the regressions.

Conclusions

Over two decades, non-leisure physical activity was associated with a substantial reduction in all-cause mortality. These results contribute to a growing number of studies that support the importance of measuring all physical activity.

Introduction

It is well established that leisure-time physical activity protects against mortality 1, 2. A review of 44 studies (3), most of which assessed only leisure-time activity, documented a dose-response relationship with all-cause mortality in men and women, and in younger and older people. In addition, however, many people get substantial physical activity from non-leisure activities, particularly walking, household chores, and job-related activity. In the National Physical Activity Survey of U.S. adults, Bates et al. (4) found that total walking was almost double leisure-time walking. Half of adults in the 1990 National Health Interview Survey who reported no leisure-time activity spent at least an hour a day on hard physical activity at work (5). In a 1999–2000 national survey, 22% of women and 29% of men said they did not engage in leisure-time activity because they got enough activity on the job (6). Non-leisure activity is an important component of total activity for certain occupational groups (7), elderly women caregivers (8), and some minority groups 9, 10 but not others (11).

The effects of non-leisure physical activity on health have not, however, been studied as extensively as those of leisure-time activity. Most studies have examined outcomes other than all-cause mortality, over brief periods of time or cross-sectionally, in samples limited by health or geography. Lee and Skerrett (3) reviewed seven studies that analyzed occupational activity separately: three found no association (Israel, Italy, Sweden) (Rosengren and Wilhelmsen [12]), three found decreased risk (Britain, Denmark, Sweden), and one found increased risk (California); three other studies included occupational activity in total physical activity, finding reduced risk. Studies have also found more non-leisure activity associated with reduced risk of cancer (13), acute myocardial infarction (14), diabetes (15), and obesity 16, 17. Higher levels of total physical activity are associated with fewer unhealthy days (18), reduced risk of type 2 diabetes (19), reduced risk of rectal cancer (20), and lower mortality in men 21, 22 and in women (22). Weller and Corey (23) attributed lower all-cause mortality in Canadian women primarily to non-leisure activity. Davis et al. (24) found that non-leisure activity predicted all-cause mortality over 10 years in U.S. adults, but leisure-time activity did not.

We analyze the first National Health and Nutrition Examination Survey (NHANES I, 1971–1975) and its Epidemiologic Followup Study (NHEFS). This survey asked about both types of physical activity at baseline. Davis et al. (24) analyzed mortality from baseline to the period 1982-1984. We analyzed mortality through 1992, an additional decade of follow-up. The outcome—all-cause mortality, the large and nationally representative sample, and the long follow-up make the analysis a unique addition to the literature on total physical activity.