1. The recommended amount of physical activity provides most of the mortality benefit. The upper limit of mortality benefit appears to occur at 3 to 5 times the recommended physical activity minimum.
2. There does not appear to be an elevated mortality risk with physical activity levels as high as 10 times the recommended minimum.
Evidence Rating Level: 1 (Excellent)
Study Rundown: The 2008 Physical Activity Guidelines for Americans recommend a minimum of 75 vigorous-intensity or 150 moderate-intensity exercise minutes per week to help reduce one’s risk of mortality. However, the upper limit of safety has not been quantified. This pooled analysis aims to calculate the dose-response relationship between leisure time physical activity (LTPA) and mortality and also determine the upper limit of benefit or harm with increased levels of physical activity.
Achieving the minimum recommended exercise guidelines resulted in a 30% reduction in mortality risk. There was reduction in mortality risk even if one did less than the minimum recommended as compared to individuals that do not partake in physical activity. The upper limit of mortality benefit occurred at 3 to 5 times the physical activity recommendation. Strengths of this study include having an extended follow-up time to analyze a novel outcome, whereas limitations of this study include use of self-reported physical activity, which may be subjected to recall bias.
Relevant Reading: Body-Mass Index and mortality among 1.46 million white adults
In-Depth [pooled analysis]: This pooled analysis used 6 cohorts from the National Cancer Institute Cohort Consortium analyses. Studies included were of prospective design, at least 5-years of follow-up, and tracked many baseline characteristics including BMI, smoking status, and LTPA. The six studies resulted in a population of 661,137 men and women, with 116,686 deaths. The exposure of interest was leisure time moderate- to vigorous-intensity physical activity. Outcomes analyzed were the upper limit of mortality benefit from high levels of LTPA. Cox proportional hazards regression with cohort stratification was used for statistical analysis.
In individuals that performed less than the recommended minimum, there was 20% lower mortality risk (HR 0.80, 95% CI 0.78-0.82) as compared to individuals who reported no leisure time physical activity. Reductions in mortality risk continued with increasing LTPA: 31% lower risk at 1-2 times the recommended minimum (HR 0.69, 95% CI 0.67-0.70), and 37% lower mortality risk at 2-3 times the recommended minimum (HR 0.63, 95% CI 0.62-0.65). The upper threshold of mortality benefit occurred at 3-5 times the LTPA recommendations, with 39% mortality risk reduction.
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