Prolonged, Uninterrupted Sitting Associated with Higher Mortality Risk

Longer total time spent sitting and periods of uninterrupted sitting are associated with a higher risk for all-cause mortality, according to the findings of a recent study.

In their prospective cohort study, the researchers used hip-mounted accelerometers to objectively measure sedentary behavior among 7985 black and white adults who were over 45 years of age and living in the United States.
__________________________________________________________________________________________________________
RELATED CONTENT
Sedentary Time Linked to Increased Mortality Risk in Frail Adults
Even Short-Term Sedentary Behavior Raises Risk of Chronic Disease
__________________________________________________________________________________________________________
The mean sedentary bout length was defined as prolonged, uninterrupted time spent sitting, and participants were categorized into 4 quartiles based on their sedentary time. Cut points for the total volume of sedentary time for quartiles 2, 3, and 4 were 689.7, 746.5, and 799.4 minutes per day, respectively. For sedentary bout duration, cut points were 7.7, 9.6, and 12.4 minutes per bout, respectively. Comparisons between quartiles 2 through 4 with quartile 1 were used to calculate hazard ratios, which included models that adjusted for moderate or vigorous physical activity.

During the median 4 years of follow-up, 340 participants died.

The researchers’ analysis showed that greater total volume of sedentary time and longer uninterrupted sedentary time were associated with higher risks for all-cause mortality across all quartiles. Hazard ratios for those with the greatest total sedentary time and longest uninterrupted sedentary time were 1.22 and 1.03 for quartile 2, 1.61 and 1.22 for quartile 3, and 2.63 and 1.96 for quartile 4.

In addition, analyses that evaluated the association between total sedentary time and bout duration showed that participants that had both the highest time spent sitting and longest bouts of sedentary time had the highest risk of death.

“Both the total volume of sedentary time and its accrual in prolonged, uninterrupted bouts are associated with all-cause mortality, suggestive that physical activity guidelines should target reducing and interrupting sedentary time to reduce risk for death,” the researchers concluded.

—Melissa Weiss

Reference:

Diaz KM, Howard VJ, Hutto B, et al. Patterns of sedentary behavior and mortality in U.S. middle-aged and older adults: a national cohort study [published online before print September 12, 2017]. Ann Intern Med. doi:10.7326/M17-0212.