Accelerometer-Measured Sedentary Patterns Are Associated with Incident Falls in Older Women.

Background/Objective Falls cause significant problems for older adults. Sedentary time is associated with lower physical function and could increase the risk for falls. Design Prospective study. Setting Sites across the United States. Participants Older women (N = 5,545, mean age 79 years) from the Women' Health Initiative Objective Physical Activity and Cardiovascular Health study. Measurements Accelerometers worn at the hip for up to 1 week collected measures of daily sedentary time and the mean sedentary bout duration, a commonly used metric for sedentary accumulation patterns. For up to 13 months after accelerometer wear, women reported daily whether they had fallen on monthly calendars. Results In fully adjusted models, the incident rate ratios (95% confidence interval) for quartiles 1 (lowest), 2, 3, and 4 of sedentary time respectively were 1.0 (ref.), 1.07 (0.93-1.24), 1.07 (0.91-1.25), and 1.14 (0.96-1.35; P-trend = .65) and for mean sedentary bout duration was 1.0 (ref.), 1.05 (0.92-1.21), 1.02 (0.88-1.17), and 1.17 (1.01-1.37; P-trend = .01), respectively. Women with a history of two or more falls had stronger associations between sedentary time and falls incidence compared with women with a history of no or one fall (P for interaction = .046). Conclusions Older women in the highest quartile of mean sedentary bout duration had a significantly increased risk of falling. Women with a history of frequent falling may be at higher risk for falling if they have high sedentary time. Interventions testing whether shortening total sedentary time and/or sedentary bouts lowers fall risk are needed to confirm these observational findings.