Replacing Sitting With Physical Activity May Lower Risk of Death

Roxanne Nelson, RN, BSN

April 01, 2019

Cutting back on "sitting time" and replacing it with even light physical activity could potentially reduce the risk of premature death, according to new findings.

Replacing 30 minutes per day of sitting time with either light physical activity (LPA) or moderate-to-vigorous physical activity (MVPA) was associated with a lower risk of mortality, although this varied according to activity level.

Among adults who were low to moderately active, replacing sitting with LPA was associated with a reduction in cancer, cardiovascular disease (CVD), and all-cause mortality. Greater mortality benefits were observed when sitting time was replaced with MVPA.

The study was published March 21 in the American Journal of Preventive Medicine.

"The take-home message is that replacing some sitting time with even light intensity physical activities, such as gardening or taking a leisurely walk, may be beneficial for those who are currently inactive, and replacing sitting time with more intense physical activities is associated with even greater health benefits," said lead author Erika Rees-Punia, PhD, MPH, a postdoctoral fellow at the American Cancer Society.

Replacing 30 minutes a day of sitting with light physical activity was associated with a 14% reduced risk of death while MVPA was associated with a 45% reduced risk of death among those who were inactive, she explained. "In our study, this included participants who exercise 17 minutes per day or less."

The benefit was less pronounced among adults who were less sedentary. "For those who are a little more active, replacing 30 minutes a day of sitting with light intensity physical activity was associated with a 6% reduced risk of death, while replacement with moderate-to-vigorous physical activity was associated with a 17% reduced risk of death," Rees-Punia told Medscape Medical News.

More Activity, Better Results

Physical activity has been associated with a lower risk of certain cancers as well as CVD and premature death. A large and ever growing body of evidence has demonstrated the benefits of exercise in not only helping to mitigate cancer risk, but also in improving outcomes in cancer patients, both during and after active treatment.

The authors note that most previous studies have explored the potential effect of sedentary time without taking into account the physical activity it displaces, and thus leaving a gap in the understanding of the issue. In this study, Rees-Punia and colleagues looked at the estimated mortality risks associated with replacing 30 minutes/day of sitting time with either LPA or MVPA.

The cohort included 92,541 individuals who participated in the American Cancer Society's Cancer Prevention Study-II Nutrition Cohort, and the analysis reviewed sedentary time and activity levels over a period of 15 years (1999–2014). A total of 14,415 men and 13,358 women died during the follow-up period.

Participants who reported higher levels of activity tended to be more highly educated and were less likely to be current smokers. Sedentary time primarily included watching TV (39%) and reading (20%).

Overall, switching 30 minutes/day of sitting to LPA (hazard ratio [HR], 0.94) or MVPA (HR, 0.92) was associated with significant reductions in the risk of mortality.

But replacing sitting with LPA was associated with a reduced mortality risk only for adults who were only low (HR, 0.86) and moderately (HR, 0.94) active, but not for those who were highly active.

Greater benefits were observed when sitting time was replaced with MVPA (low active, HR = 0.55; moderately active, HR = 0.83).

Similar results were seen for cancer mortality with LPA (low active, HR = 0.90; high active, HR = 1.01) and for MVPA (low active, HR = 0.53; high active, HR = 1.00).

The findings were similar when stratified by gender and body mass index, but there were significant interactions by age that showed there were larger mortality benefits for older adults who replaced sitting with LPA.

"We did explore the role of age on the replacement of sitting time and found that older adults, 75 years and above, may benefit from replacing sitting time with light-intensity physical activity more than younger adults," said Rees-Punia.

The American Cancer Society funded the Cancer Prevention Study-II. Rees-Punia and study coauthors have disclosed no relevant financial relationships.

American Journal of Preventive Medicine. Published online March 21, 2019.
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