Researchers have found that adults who sit for one or two hours at a time without moving have a much higher mortality rate than those who sat for just as long but over shorter periods of time. Their study is the largest to date that links objectively measured sedentary time, sedentary patterns, and mortality risk.
"We tend to think of sedentary behavior as just the sheer volume of how much we sit around each day," said lead investigator Dr. Keith Diaz. "But previous studies have suggested that sedentary patterns -- whether an individual accrues sedentary time through several short stretches or fewer long stretches of time -- may have an impact on health."
Sitting time and greater mortality risk
To gather data, the researchers asked nearly 8,000 participants to wear hip-mounted activity monitors during their waking hours over a week-long period. The devices showed that, on average, sedentary behaviors accounted for 77% of a participant’s day, the equivalent of around 12 hours.
During a prevailing four-year follow-up period, 340 of the participants died. After comparing the data, the researchers found that mortality risk was highest in individuals who had more than 13 hours of sedentary time per day. Worse yet, they found that those who had sedentary periods lasting from 60-90 minutes were twice as likely to die than those who had shorter periods of sedentary time.
The researchers say that out of all sedentary participants, those who kept their sitting time limited to 30 minutes had the lowest risk of death. The finding adds credence to many workplace recommendations for employees to get up and move around periodically.
"If you have a job or lifestyle where you have to sit for prolonged periods of time, we suggest taking a movement break every half hour," said Diaz. "This one behavior change could reduce your risk of death, although we don't yet know precisely how much activity is optimal."
Sitting is the new smoking
Dr. Monnika Safford says that the study findings also reinforce current efforts by doctors and clinicians to discourage sedentary behaviors.
"This study adds to the growing literature on how dangerous long periods of sitting are for our health, and underscores a growing awareness among clinicians and researchers that sitting really is the new smoking," she said.
"We need creative ways to ensure that we not only cut back on the total amount we sit, but also increase regular interruptions to sitting with bursts of activity.”
Two papers [1,2] connected to the study have been published in the Annals of Internal Medicine.