Physical activity and/or sedentary behaviour and the development of functional disability in community-dwelling older adults in Tsuru, Japan: a prospective cohort study (the Tsuru Longitudinal Study)

OBJECTIVES: To clarify the association between moderate-to-vigorous physical activity (MVPA) and/or sedentary behaviour (SB) and the incidence of functional disability (FD) in older adults. DESIGN: Prospective cohort study. SETTING: Local municipality of Tsuru, Yamanashi, Japan. We conducted a baseline survey in January 2016. Follow-up was commenced on 1 February 2016 and completed on 31 October 2018. PARTICIPANTS: All individuals (6661 people) aged >65 years who were independently living in the community were eligible. METHODS AND OUTCOME MEASURES: MVPA (min/week) and SB (min/day) were measured using self-administered questionnaires in 5311 independently living older adults who participated in this study. The follow-up period was 33 months, and the incidence of FD was objectively determined by experts. The participants were divided into three groups based on MVPA distribution (non-MVPA, 0 min; short-MVPA, 1–299 min and long-MVPA, ≥300 min/week) and into two groups based on the median value of SB (short-SB,<190 min; and long-SB, ≥190 min/day). The participants were also classified into six categories based on different combinations of MVPA and SB. Cox proportional hazards model was used to calculate the HR and 95% CI for FD development with MVPA, SB and a combination of these behaviours. RESULTS: Among the included participants, 2415 were male and 2896 were female. The mean ages (SD) of the male and female participants were 74.5 (6.8) and 74.9 (6.9) years, respectively. The total number of participants with chronic conditions was 3489 (65.7%). Using the non-MVPA group as the reference, the multivariable-adjusted HR (95% CI) was 0.68 (0.54 to 0.84) in the short-MVPA group and 0.53 (0.41 to 0.69) in the long-MVPA group. Regarding SB, the short-SB group had an HR of 0.86 (0.71 to 1.03) compared with the long-SB group. The combined behaviour showed the lowest HR in the long-MVPA and short-SB group 0.49 (0.34 to 0.72) and the long-MVPA and long-SB group 0.49 (0.34 to 0.68), respectively. CONCLUSIONS: Long-MVPA had a robust association with FD development, whereas short-SB had a modest association. Moreover, a combination of these behaviours had a stronger association than individual behaviours. If the identified associations are assumed to be causal in nature, these findings suggest that encouraging older adults to engage in MVPA and reduce SB in their daily lives could be effective to prevent or delay FD development.