Excessive sedentary time, whether accumulated throughout the day or accrued in prolonged, uninterrupted bouts, is a significant risk factor for all-cause mortality, regardless of exercise habits. Taking movement breaks every 30 minutes throughout the day could help to mitigate the negative health effects of too much sitting. These findings suggest that physical activity guidelines should target reducing and interrupting sedentary time in addition to setting daily goals for moderate- to vigorous-intensity physical activity. The study is published in Annals of Internal Medicine.
Adults are sedentary for an alarming 9 to 10 hours per day. Previous studies showing a link between sedentary behavior and death have relied on self-reporting to evaluate the total volume of sedentary time and did not examine whether the manner in which sedentary time is accrued (in short or long bouts) carries prognostic relevance.
Researchers at Columbia University Medical Center, NewYork-Presbyterian/Weill Cornell Medical Center and other institutions studied a national cohort of 7,985 black and white adults aged 45 years or older to examine the association between sedentary behavior (its total volume and accrual in prolonged, uninterrupted bouts) and all-cause mortality. Sedentary time was objectively measured using a hip-mounted accelerometer. All-cause mortality was the primary outcome, defined as any death after completion of the accelerometer protocol, regardless of cause.
The data showed that sedentary behavior accounted for about 12.3 hours per day over a 16-hour waking day. Mean sedentary bout length was 11.4 minutes. Over a median follow-up of 4 years, 340 participants died. Greater total sedentary time and longer mean sedentary bout duration each had a dose-dependent association with higher risk for all-cause mortality that did not vary by age, sex, race, BMI, or participant exercise habits. Participants who kept their sitting bouts to less than 30 minutes had the lowest risk for death. According to the authors, these findings suggest that taking a break from sitting every half hour could help to mitigate the negative effects of sedentary time.