A new study finds that it’s not just the amount of time you spend sitting, but also the way in which sitting time is accumulated during the entire day that can affect the risk of early death.
According to the study published this month in Annals of Internal Medicine, adults who sit for one to two hours at a time without moving have higher mortality rates when compared to adults who accrue the same amount of sedentary time in shorter bouts.
“We tend to think of sedentary behaviour as just the sheer volume of how much we sit around each day,” said Dr. Keith Diaz, associate research scientist in the Department of Medicine at Columbia University Medical Center (CUMC) and lead investigator of the study. “But previous studies have suggested that sedentary patterns – whether an individual accrues sedentary time through several short stretches or fewer long stretches or fewer long stretches of time – may have an impact on health.”
A hip-mounted activity monitor was used to measure inactivity during waking time over a period of seven days in 7,985 black and white adults over 45 years old.
On average, sedentary behaviour accounted for 77 percent of the participants’ waking hours, equivalent to more than 12 hours per day. Over a median follow-up period of four years, 340 of the subjects died. Mortality risk was calculated for those with various amounts of total sedentary time and various sedentary patterns. Those with sedentary times of more than 13 hours per day, and who frequently had sedentary bouts of at least 60 to 90 consecutive minutes had a nearly two-fold increase in death risk compared to those who had least total sedentary time and the shortest sedentary bouts.
Researchers also found that those who kept most of their sitting bouts to less than 30 minutes had the lowest risk of death.
“So 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. This one behaviour change could reduce your risk of death, although we don’t know precisely how much activity is optimal,” said Dr. Diaz.
“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,” said study co-author Dr. Monika Safford. “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.”
The participants were taking part in the REGARDS study, which is a national investigation of racial and regional disparities in stroke. Dr. Safford is the PI on one of the REGARDS ancillary studies and provided the cardiac events data for this paper.