Association of 12-Year Trajectories of Sitting Time With Frailty in Middle-Aged Women

Prolonged sitting time is associated with several health outcomes; limited evidence indicates associations with frailty. Our aims in this study were to identify patterns of sitting time over 12 years in middle-aged (ages 50-55 years) women and examine associations of these patterns with frailty in older age. We examined 5,462 women born in 1946-1951 from the Australian Longitudinal Study on Women's Health who provided information on sociodemographic attributes, daily sitting time, and frailty in 2001 and then again every 3 years until 2013. Frailty was assessed using the FRAIL (fatigue, resistance, ambulation, illness, loss of weight) scale (0 = healthy; 1-2 = prefrail; 3-5 = frail), and group-based trajectory analyses identified trajectories of sitting time. We identified 5 sitting-time trajectories: low (26.9%), medium (43.1%; referent), increasing (6.9%), decreasing (18.1%), and high (4.8%). In adjusted models, the likelihoods of being frail were statistically higher for women in the increasing (odds ratio (OR) = 1.29, 95% confidence interval (CI): 1.03, 1.61) and high (OR = 1.42, 95% CI: 1.10, 1.84) trajectories. In contrast, women in the low trajectory group were less likely to be frail (OR = 0.86, 95% CI: 0.75, 0.98), and there was no difference in the likelihood of frailty in the decreasing trajectory group. Our study suggests that patterns of sitting time over 12 years in middle-aged women predict frailty in older age.