Leisure time physical activity and mortality: a detailed pooled analysis of the dose-response relationship

Abstract

Importance: The 2008 Physical Activity Guidelines for Americans recommended a minimum of 75 vigorous-intensity or 150 moderate-intensity minutes per week (7.5 metabolic-equivalent hours per week) of aerobic activity for substantial health benefit and suggested additional benefits by doing more than double this amount. However, the upper limit of longevity benefit or possible harm with more physical activity is unclear.

Objective: To quantify the dose-response association between leisure time physical activity and mortality and define the upper limit of benefit or harm associated with increased levels of physical activity.

Design, setting, and participants: We pooled data from 6 studies in the National Cancer Institute Cohort Consortium (baseline 1992-2003). Population-based prospective cohorts in the United States and Europe with self-reported physical activity were analyzed in 2014. A total of 661,137 men and women (median age, 62 years; range, 21-98 years) and 116,686 deaths were included. We used Cox proportional hazards regression with cohort stratification to generate multivariable-adjusted hazard ratios (HRs) and 95% CIs. Median follow-up time was 14.2 years.

Exposures: Leisure time moderate- to vigorous-intensity physical activity.

Main outcomes and measures: The upper limit of mortality benefit from high levels of leisure time physical activity.

Results: Compared with individuals reporting no leisure time physical activity, we observed a 20% lower mortality risk among those performing less than the recommended minimum of 7.5 metabolic-equivalent hours per week (HR, 0.80 [95% CI, 0.78-0.82]), a 31% lower risk at 1 to 2 times the recommended minimum (HR, 0.69 [95% CI, 0.67-0.70]), and a 37% lower risk at 2 to 3 times the minimum (HR, 0.63 [95% CI, 0.62-0.65]). An upper threshold for mortality benefit occurred at 3 to 5 times the physical activity recommendation (HR, 0.61 [95% CI, 0.59-0.62]); however, compared with the recommended minimum, the additional benefit was modest (31% vs 39%). There was no evidence of harm at 10 or more times the recommended minimum (HR, 0.69 [95% CI, 0.59-0.78]). A similar dose-response relationship was observed for mortality due to cardiovascular disease and to cancer.

Conclusions and relevance: Meeting the 2008 Physical Activity Guidelines for Americans minimum by either moderate- or vigorous-intensity activities was associated with nearly the maximum longevity benefit. We observed a benefit threshold at approximately 3 to 5 times the recommended leisure time physical activity minimum and no excess risk at 10 or more times the minimum. In regard to mortality, health care professionals should encourage inactive adults to perform leisure time physical activity and do not need to discourage adults who already participate in high-activity levels.

Figure 1. Hazard ratios (HRs) and 95% confidence intervals (CIs) for leisure time moderate- to vigorous-intensity physical activity and mortality^a-c

The dose-response curve and category-specific hazard ratio estimates for leisure time moderate- to vigorous-intensity physical activity and mortality. Crude and adjusted risk estimates are presented in eTable3. Exercise levels compared to the federally recommended minimum of 7.5 MET h/wk ^aModels were stratified by cohort and use age as the underlying time scale. The model was adjusted for gender, smoking (never, former, current, missing), alcohol (none, <15 grams/day, 15–30 grams/day, 30+ grams/day), education (dropout, high school, post high school education, some college, college graduate, post-college, missing), marital status (married, divorced, widowed, single, missing), history of cancer, history of heart disease, and body mass index (<18.5, 18.5–25, 25-<30, 30-<35, 35+ kg/m²). ^bThe dotted line between categories illustrates an assumed dose-response rather than individual data points. ^cCrude and adjusted hazard ratios and 95% confidence intervals are presented in Supplemental Table 3.