“Sitting is the new smoking” has now got the backing of hard data. Doing a little more physical activity each day and reducing time spent sitting may go a long way in preventing premature deaths, according
to a large international study.
Health warnings about too much sitting are not new. What is new is the scale of evidence. The study, published in the medical journal The Lancet, pooled individual-level data from nine prospective cohort studies from more than 135,000 adults across the UK, the US, and Scandinavia. By analysing physical activity and sedentary time as continuous exposures rather than broad categories, researchers sought to estimate the health impact of realistic, incremental behaviour changes rather than idealised targets.
“Small and realistic increases in moderate-to-vigorous intensity physical activity (MVPA) of 5 minutes per day might prevent up to 6% of all deaths in a high-risk approach and 10% of all deaths in population-based approach. Reducing sedentary time by 30 minutes per day might prevent a smaller, but still meaningful, proportion of deaths in the two risk scenarios,” said the report.
The study has been authored by a group of 20 researchers representing several educational organisations, including the Norwegian School of Sports Science, the Norwegian Institute of Public Health, the Sydney School of Public Health, the University of Vigo in Spain, the University of Sydney, the University of Alabama at Birmingham, and the Department of Epidemiology, Harvard TH Chan School of Public Health, USA.
What did the study find?
The analysis found that increases in moderate-to-vigorous physical activity (MVPA) were strongly associated with lower all-cause mortality, particularly among individuals who were least active at baseline. Among participants accumulating around one minute of MVPA per day, increasing activity to six minutes per day was associated with approximately a 30% reduction in mortality risk. Increasing MVPA from one minute to about 11 minutes per day was linked to an estimated 42% lower risk of death.
However, the benefits were not linear across the activity spectrum. While mortality risk continued to decline with higher levels of MVPA, the magnitude of benefit diminished beyond roughly 20 to 25 minutes per day, suggesting diminishing returns at higher activity levels.
Using population impact modelling, the researchers estimated that if all participants increased their MVPA by five minutes per day, approximately 6% of deaths could potentially be prevented. A ten-minute increase in daily MVPA was associated with an estimated 10% reduction in deaths at the population level. These estimates were driven largely by gains among the least active participants, reinforcing the importance of targeting those at the lower end of the activity distribution.
Cutting sitting time matters, especially for the most sedentary
The study also examined sedentary time independently of physical activity and found that reducing daily sitting time was associated with lower mortality risk, though the relationship varied by baseline levels of sedentariness.
Among individuals spending more than eight hours per day sedentary, reducing sitting time by 30 minutes per day was associated with meaningful reductions in mortality risk. A 60-minute reduction in daily sedentary time was linked to even larger benefits, particularly among those sitting for more than ten hours a day. In this group, a 60-minute reduction in sedentary time was associated with an estimated 25% lower risk of death.
“Reducing sedentary time by 30 minutes per day might prevent 3 per cent of all deaths in the high-risk approach and 7.3% in the population-based approach. Results from the UK Biobank were of a smaller magnitude but still substantial—e.g., reducing sedentary time by 30 minutes per day in all except the most active participants was associated with preventing 4.5% of total deaths,” the study noted.
By contrast, reductions in sedentary time were not consistently associated with lower mortality risk among participants who already spent relatively little time sitting, highlighting that interventions may need to be tailored to baseline behaviour.
Realistic targets over idealised guidelines
A key contribution of the study is its focus on realistic, achievable changes rather than theoretical scenarios such as eliminating sedentary behaviour altogether, an approach commonly used in earlier research.
Instead, the findings suggest that even small shifts—adding a few minutes of brisk walking or reducing prolonged sitting—can deliver substantial population-level health gains when adopted broadly.
The analysis used harmonised accelerometer data and adjusted for multiple confounders, including age, sex, smoking, body mass index, pre-existing cardiovascular disease, cancer, and diabetes. Sensitivity analyses excluding early deaths and participants with mobility limitations yielded similar results.
“Our approach has several strengths. Analyses are based on small and realistic changes in device-measured physical activity and sedentary time and take into account the non-linear shape of the association between activity levels and mortality,” the authors of the study noted while concluding that public health strategies should prioritise helping the most inactive and most sedentary individuals. These individuals should be encouraged to make small, sustainable changes, rather than focusing solely on achieving recommended activity thresholds that may be unrealistic for large sections of the population.
