A new study finds that it isn’t just the amount of time spent sitting, but also the way in which sitting time is accumulated during the day, that can affect risk of early death.
The study, published online today in Annals of Internal Medicine, found that adults who sit for one to two hours at a time without moving have a higher mortality rate than 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 Keith Diaz, PhD, 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 of time–may have an impact on health.”
The researchers used hip-mounted activity monitors to objectively measure inactivity during waking time over a period of seven days in 7,985 black and white adults over age 45. (The participants were taking part in the REGARDS study, a national investigation of racial and regional disparities in stroke.)
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 participants died. Mortality risk was calculated for those with varying amounts of total sedentary time and various sedentary patterns. Those with the greatest amount of sedentary time–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 with those who had the least total sedentary time and the shortest sedentary bouts.
The researchers also found that participants 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 yet know precisely how much activity is optimal,” Dr. Diaz said.
The study was the largest to link objectively measured sedentary time and sedentary patterns with mortality risk.
“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 Monika Safford, MD, chief of the Division of General Internal Medicine and the John J. Kuiper Professor at Weill Cornell Medicine, and an internist at NewYork-Presbyterian/Weill Cornell Medical Center. “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.” Dr. Safford is the PI on one of the REGARDS ancillary studies and provided the cardiac events data for this paper.
The study is titled, “Patterns of sedentary behavior and mortality in U.S. middle-aged and older adults: A national cohort study.”
The other authors are: Virginia J. Howard (University of Alabama at Birmingham, Birmingham, AB), Brent Hutto (UAB), Natalie Colabianchi (University of Michigan, Ann Arbor, MI), John E. Vena (Medical University of South Carolina, Charleston, SC), Steven N. Blair (University of South Carolina, Columbia, SC), and Steven P. Hooker (Arizona State University, Phoenix, AZ).
The study was supported by the National Institutes of Health (UO1-NS041588 and R01-NS061846) and the Coca-Cola Company.
The authors report no financial or other conflicts of interest.
Columbia University Medical Center provides international leadership in basic, preclinical, and clinical research; medical and health sciences education; and patient care. The medical center trains future leaders and includes the dedicated work of many physicians, scientists, public health professionals, dentists, and nurses at the College of Physicians and Surgeons, the Mailman School of Public Health, the College of Dental Medicine, the School of Nursing, the biomedical departments of the Graduate School of Arts and Sciences, and allied research centers and institutions. Columbia University Medical Center is home to the largest medical research enterprise in New York City and State and one of the largest faculty medical practices in the Northeast. The campus that Columbia University Medical Center shares with its hospital partner, NewYork-Presbyterian, is now called the Columbia University Irving Medical Center. For more information, visit cumc.columbia.edu or columbiadoctors.org.
Weill Cornell Medicine
Weill Cornell Medicine is committed to excellence in patient care, scientific discovery and the education of future physicians in New York City and around the world. The doctors and scientists of Weill Cornell Medicine — faculty from Weill Cornell Medical College, Weill Cornell Graduate School of Medical Sciences, and Weill Cornell Physician Organization — are engaged in world-class clinical care and cutting-edge research that connect patients to the latest treatment innovations and prevention strategies. Located in the heart of the Upper East Side’s scientific corridor, Weill Cornell Medicine’s powerful network of collaborators extends to its parent university Cornell University; to Qatar, where an international campus offers a U.S. medical degree; and to programs in Tanzania, Haiti, Brazil, Austria and Turkey.
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