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Updated: Sep 28, 2026
Visualization of Intensity Levels to Reduce the Gap Between Self-Reported and Directly Measured Physical Activity
Published on: March 7, 2019
Red Light, Green Light: Activity Fragmentation and All-Cause Mortality in United States Adults
1School of Business, Maynooth University, Maynooth, Co. Kildare, W23 F2H6, Ireland; Universidade Católica Portuguesa, Católica Porto SBE, Research Center in Management and Economics, Rua de Diogo Botelho 1327, 4169-005 Porto, Portugal.
Purpose:
Physical-activity epidemiology treats how much people move as the health-relevant exposure. We asked whether activity fragmentation, the probability that movement gives way to rest, predicts all-cause mortality independently of activity volume, and how the two compare as predictors.
Methods:
In a prospective cohort analysis, we pooled the 2003-2004 and 2005-2006 cycles of the National Health and Nutrition Examination Survey, which used the same hip-worn accelerometer and protocol, and linked them to mortality through 2019. Adults aged 20 years or older with at least four valid wear days were eligible (N = 5,973). Fragmentation was the active-to-sedentary transition probability. Survey-weighted Cox models adjusted for volume, demographic and socioeconomic characteristics, smoking, alcohol, hypertension, diabetes and cardiovascular history.
Results:
Over a median 14.4 years, 1,429 participants died. Each standard-deviation increase in fragmentation carried a 19% higher hazard of death (hazard ratio 1.19, 95% confidence interval 1.09-1.30). Volume remained protective in the same model (0.83, 0.75-0.92). Fragmentation added more to a model containing volume than volume added to one containing fragmentation. Higher education predicted more fragmented movement; income did not.
Conclusions:
Activity fragmentation carries mortality information that activity volume does not, and is the stronger of the two predictors.
