Activity fragmentation predicts mortality risk in adults
In US adults, each standard-deviation rise in activity fragmentation was linked to a 19% higher hazard of death after adjusting for activity volume.
Annals of Epidemiology
In a prospective cohort of 5,973 United States adults aged 20 or older, researchers examined whether activity fragmentation predicted all-cause mortality independently of total movement volume. They pooled data from two NHANES cycles using hip-worn accelerometers and tracked participants over a median of 14.4 years, recording 1,429 deaths. Fragmentation was defined as the probability of transitioning from an active state to a sedentary one. Each standard-deviation increase in fragmentation carried a 19% higher hazard of death (hazard ratio 1.19, 95% confidence interval 1.09-1.30) after adjusting for volume and health factors. Activity volume remained protective (hazard ratio 0.83, 95% confidence interval 0.75-0.92). Fragmentation added more to a model containing volume than volume added to one containing fragmentation.
Why it matters
The findings indicate that the inability to sustain continuous bouts of movement may signal physiological decline. How movement is accumulated over time could be a more sensitive indicator of biological aging and resilience than total daily activity.
Caveats
The observational design cannot establish that activity fragmentation directly causes earlier mortality. Physical activity was also measured using hip accelerometers during a single baseline period of at least four wear days.
The paper
Red light, green light: Activity fragmentation and all-cause mortality in United States adults
Universidade Católica Portuguesa
Annals of Epidemiology · 26 Sep 2026