Moderate-to-Vigorous Physical Activity and All-Cause Mortality: Do Bouts Matter?
Level 3 - non-randomized controlled study
Prospective observational cohort study linking objective baseline survey data to mortality registry records.
PubMed 29567764 · doi:10.1161/JAHA.117.007678
What was done
Analyzed data from the National Health and Nutrition Examination Survey (NHANES) 2003–2006 linked to National Death Index records through 2011 (mean follow-up ≈6.6 years; 700 deaths) in 4,840 US adults aged 40 years and older. Accelerometer-measured physical activity was processed to determine total daily minutes of moderate-to-vigorous physical activity (MVPA) and bouted MVPA (defined as bouts lasting ≥5 or ≥10 minutes, permitting 1- to 2-minute interruptions). Hazard ratios for all-cause mortality were estimated across activity quartiles and joint classifications of total MVPA and proportion of bouted activity.
What was found
Hazard ratios for all-cause mortality were comparable between total and bouted activity, ranging from 0.24 for the third quartile of total MVPA to 0.44 for the second quartile of 10-minute bouts. Joint classification analyses of total MVPA quartiles and tertiles of bouted activity proportion demonstrated that accumulating MVPA in bouts did not confer additional mortality risk reduction beyond total volume.
Why it matters
These findings indicate that mortality reductions from physical activity depend on total accumulated duration rather than session length, supporting guideline revisions that remove the requirement for minimum 10-minute bouts.
Limits
Observational design prevents causal inference and leaves room for residual confounding or reverse causality. Physical activity was measured at a single baseline snapshot and may not reflect habit changes across the 6.6-year follow-up. The study was limited to adults aged 40 and older and did not report cause-specific mortality in the abstract.
Cited by
- supports Physical activity guidelines previously required moderate or vigorous exercise to be accumulated in bouts of at least 10 minutes, but that minimum bout duration was removed from the guidelines.