When researchers talk about “sedentary time,” they usually mean waking time spent sitting, reclining, or lying down with very low energy use (think desk work, TV, long car rides).
Across large population studies and reviews, a common pattern shows up: as daily sedentary time climbs into the ~8–10 hours/day range, average risk for outcomes like cardiovascular disease and earlier mortality tends to increase.
A key nuance is that this is not a clean threshold where “8 hours is safe and 10 is unsafe.” It’s more like a risk curve: more sedentary time is generally worse, and risk also depends on what surrounds the sitting—overall physical activity level, fitness, and whether sitting is broken up or sustained in long bouts.
Sources
- https://pmc.ncbi.nlm.nih.gov/articles/PMC6532816/
- https://www.psychiatrist.com/jcp/physical-exercise-and-health-5-sedentary-time-and-risk-of-adverse-outcomes/
- https://www.massgeneralbrigham.org/en/about/newsroom/articles/sedentary-time-cardiovascular-health
- https://www.sbm.org/healthy-living/move-more-and-sit-less-how-to-reduce-sedentary-time
- https://en.wikipedia.org/wiki/Sedentary_lifestyle
