Washington: For those who get the least amount of physical activity, replacing half an hour of sitting time with physical activity was associated with up to nearly 50 per cent reduction in mortality.
The study appeared in the American Journal of Preventive Medicine, suggested that replacing the modest amount of sitting time with even light physical activity may have the potential to reduce the risk of premature death among less active adults.
Light or moderate to vigorous physical activity (MVPA) is associated with a lower risk of cardiovascular disease; certain cancers; and premature death.
In addition, the amount of time spent sedentary is associated with a higher risk of death and disease. This may be resulting, at least in part, from the displacement of physical activity with sedentary behaviours.
Most of the previous studies have explored the potential effect of sedentary time without considering the physical activity it displaces, leaving a gap in the understanding of the issue.
To explore further, investigators led by Erika Rees-Punia, PhD, analysed self-reported sitting time, light physical activity, and moderate/vigorous physical activity among 92,541 participants in the ACS's Cancer Prevention Study II Nutrition Cohort.
The analysis reviewed sedentary time and activity levels over 14 years. It found, among the least active participants (≤17minutes/day MVPA), replacing 30 minutes/day of sitting with light physical activity was associated with a 14 per cent reduced risk of death, while replacement with moderate to vigorous physical activity was associated with a 45 per cent reduced risk of death.
The investigators found similar but smaller associations among moderately active participants: replacing a half hour of sedentary time with light physical activity was associated with a 6 per cent reduction in mortality among those who were moderately active; replacing 30 minutes of sitting time with moderate to vigorous physical activity was associated with a 17 per cent mortality reduction in this group.
However, for the most active (>38 minutes/day of MVPA), substitution of sitting time with light physical activity or MVPA was not associated with a reduction in mortality risk.
Participants reporting more moderate/vigorous physical activity were leaner, had higher educational attainment, and were less likely to be current smokers. For all the participants, sitting time largely included watching TV (39 per cent) and reading (20 per cent).
The study did have some limitations: it relied on self-reported physical activity and sitting time; it lacked information on certain activities of daily living (e.g., cleaning, self-care, cooking) that are particularly common for older adults. And participants were predominately white and educated, so may not represent the general US population.
"These findings suggest that the replacement of modest amounts of sitting time even with light physical activity may have the potential to reduce the risk of premature death among less active adults," concluded the authors.
