Moderate-to-Vigorous Physical Activity and All-Cause Mortality: Do Bouts Matter?

Abstract

Background: The 2008 Physical Activity Guidelines for Americans recommends that adults accumulate moderate-to-vigorous physical activity (MVPA) in bouts of ≥10 minutes for substantial health benefits. To what extent the same amount of MVPA accumulated in bouts versus sporadically reduces mortality risk remains unclear.

Methods and results: We analyzed data from the National Health and Nutrition Examination Survey 2003-2006 and death records available through 2011 (follow-up period of ≈6.6 years; 700 deaths) to examine the associations between objectively measured physical activity accumulated with and without a bout criteria and all-cause mortality in a representative sample of US adults 40 years and older (n=4840). Physical activity data were processed to generate minutes per day of total and bouted MVPA. Bouted MVPA was defined as MVPA accumulated in bouts of a minimum duration of either 5 or 10 minutes allowing for 1- to 2-minute interruptions. Hazard ratios for all-cause mortality associated with total and bouted MVPA were similar and ranged from 0.24 for the third quartile of total to 0.44 for the second quartile of 10-minute bouts. The examination of jointly classified quartiles of total MVPA and tertiles of proportion of bouted activity revealed that greater amounts of bouted MVPA did not result in additional risk reductions for mortality.

Conclusions: These results provide evidence that mortality risk reductions associated with MVPA are independent of how activity is accumulated and can impact the development of physical activity guidelines and inform clinical practice.

Keywords: National Health and Nutrition Examination Survey; accelerometer; activity bouts; adults; epidemiology; exercise.

Figure 1

Main effects for quartile‐specific distributions of total minutes per day of moderate‐to‐vigorous physical activity (MVPA), and both ≥5‐ and ≥10‐minute bouts of accumulated minutes per day of MVPA. Quartiles: total MVPA (≤40.2, 40.2–79.5, 79.5–123.4, and >123.4 min/d); 5‐minute bouts MVPA (≤10.7, 10.7–34.3, 34.3–70.7, and >70.7 min/d); 10‐minute bouts MVPA (0.0, 0.0–5.1, 5.1–20.5, >20.5 min/d). Hazard ratios are adjusted for age, sex, race‐ethnicity, education, alcohol consumption, smoking status, body mass index, and self‐reported diagnosis of diabetes mellitus, coronary artery disease, stroke, cancer, and mobility limitation.

Figure 2

Distribution of hazard ratios provided in the Table by total duration of moderate‐to‐vigorous physical activity (MVPA) for jointly classified quartiles of total minutes and tertiles of relative contribution of bouted minutes. For example, 4,1 is equivalent to combined quartile 4 of total MVPA and tertile 1 (Table) of the relative contribution of bouted to total minutes. The relative contribution (%) of bouted MVPA minutes ranged from 3% (bright yellow) to 81% (dark red). The joint group 4,1 represents 150 minutes in total MVPA and ≈50% of the total duration was accumulated in bouts of ≥5 minutes. The remaining 50% was accumulated in sporadic activity. The grey error bars indicate the upper and lower 95% confidence intervals for respective hazard ratios. Hazard ratios are adjusted for age, sex, race‐ethnicity, education, alcohol consumption, smoking status, body mass index, and self‐reported diagnosis of diabetes mellitus, coronary artery disease, stroke, cancer, and mobility limitation.