Take a movement break every 30 minutes, say experts. No matter how much you exercise, sitting for excessively long periods of time is a risk factor for early death, a new study published Monday in Annals of Internal Medicine found.
There's a direct relationship between time spent sitting and your risk of early mortality of any cause, researchers said, based on a study of nearly 8,000 adults. As your total sitting time increases, so does your risk of an early death.
The positive news: People who sat for less than 30 minutes at a time had the lowest risk of early death.
"Sit less, move more" is what the American Heart Association encourages all of us to do. But this simplistic guideline doesn't quite cut it, said Keith Diaz, lead author of the new study and an associate research scientist in the Columbia University Department of Medicine.
"This would be like telling someone to just 'exercise' without telling them how," Diaz wrote in an email.
Exercise guidelines are precise, he explained. For example, the US Centers for Disease Control and Prevention recommends adults do moderate-intensity aerobic exercise for two hours and 30 minutes every week, plus muscle strengthening activities on two or more days a week.
"We need similar guidelines for sitting," said Diaz.
"We think a more specific guideline could read something like, 'For every 30 consecutive minutes of sitting, stand up and move/walk for five minutes at brisk pace to reduce the health risks from sitting,' " he said, adding the study "puts us a step closer to such guidelines," but more research is needed to verify the findings.
Aging means more sitting
To understand the relationship between sedentary behavior and early death, Diaz and his colleagues at Columbia, NewYork-Presbyterian/Weill Cornell Medical Center and other institutions turned to the REasons for Geographic and Racial Differences in Stroke (REGARDS) project, a study sponsored by the National Institutes of Health.
"The REGARDS study was originally designed to examine why blacks (and particularly blacks in the Southern US) have a greater risk for stroke than whites," said Diaz. He and his co-researchers tracked for an average of four years 7,985 black and white adult participants, age 45 or older, who had signed on to participate in the REGARDS project.
To measure sedentary time for these adults, the research team used hip-mounted accelerometers. During the study period, the team recorded 340 total deaths considered "all-cause mortality" -- any death, regardless of cause.
Analyzing the data, the team found that sedentary behavior, on average, accounted for about 12.3 hours of an average 16-hour waking day.
"As we age, and our physical and mental function declines, we become more and more sedentary," wrote Diaz.
Previous studies of adults have found daily sitting time to average just nine to 10 hours per day. The higher average in his own study is likely "due to the fact we studied a middle- and older-aged population," Diaz wrote. "It could also be partly due to the fact that we used an activity monitor to track sedentary time rather than using self-report."