Examining the Independent and Interactive Association of Physical Activity and Sedentary Behaviour with Frailty in Chinese Community-Dwelling Older Adults

Background: While physical inactivity or prolonged sitting has been linked to an increased risk of frailty, the interaction between sitting time (ST), physical activity (PA) and frailty is largely unknown. The aim of this study was to examine the independent and interactive association between PA, ST and frailty in Chinese community-dwelling older adults. Methods A cross-sectional analysis was performed on 1458 participants (age ≥ 60) enrolled from a prospective cohort study of frailty in elderly people of Fujian Province. PA and ST levels were assessed using the International Physical Activity Questionnaire. A 40-item frailty index (FI) quantified frailty. Multivariable logistic regression and linear regression models were applied to examine the independent association between PA or ST and frailty level. Interaction plots were used to visualise the interaction effects of PA and ST on frailty. Results Compared with light PA, the odds ratios (ORs) for frailty were significantly lower for moderate PA (OR, 0.609 [95% CI, 0.419, 0.885], P  < .001) and vigorous PA (OR, 0.399 [95% CI, 0.236,0.673], P  < .001). Comparing subjects with ST < 4 h/day, those with ST ≥ 8 h/day were significantly more likely to be diagnosed with frailty (OR, 3.140 [95% CI, 1.932, 5.106], P  < .001), 6–8 h/day (OR, 1.289 [95% CI, 0.835, 1.989], P ༞0.05), and 4–6 h/day (OR, 1.400 [95% CI, 0.972, 2.018], P ༞0.05). Each one unit increase in metabolic equivalents (h/day) of PA was related to an average 0.928 (0.887, 0.971) decrease in prevalence of frailty, while each one unit increase in sitting time (h/day) was related to average 1.114 (1.046,1.185) increase in prevalence of frailty. Negative interactive effects of PA and ST on frailty were observed ( P  < 0.001). Conclusion PA can independently reduce the occurrence of frailty, while prolonged ST can significantly increase the occurrence of frailty. In addition, excess ST may counteract the beneficial effects of PA on frailty.