Washington: For those who get the least amount of physical activity, replacing half an hour of sitting time with physical activity was associated with a nearly 50 percent reduction in mortality.
The study in the American Journal of Preventive Medicine suggested that replacing a modest amount of sitting time with even light physical activity may potentially 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 result, at least in part, from the displacement of physical activity with sedentary behaviors.
Most previous studies have explored the potential effect of sedentary time without considering the physical activity it displaces, leaving a gap in our understanding of the issue.
To explore further, investigators led by Erika Rees-Punia, PhD, analyzed 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 that among the least active participants (≤ 17 minutes/day MVPA), replacing 30 minutes/day of sitting with light physical activity was associated with a 14 percent reduced risk of death. In contrast, replacement with moderate to vigorous physical activity was associated with a 45 percent 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 percent reduction in mortality among those who were moderately active, and replacing 30 minutes of sitting time with moderate to vigorous physical activity was associated with a 17 percent mortality reduction in this group.
However, for the most active (>38 minutes/day of MVPA), substituting sitting time with light physical activity or MVPA was not associated with reducing 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 percent) and reading (20 percent).
The study did have some limitations: It relied on self-reported physical activity and sitting time, and it lacked information on certain activities of daily living (e.g., cleaning, self-care, cooking) that are particularly common for older adults. Participants were predominantly white and educated, so they 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.
