Longitudinal association of objectively measured physical activity and bioimpedance phase angle in older adults

The benefits of physical activity, including exercise and daily and household chores, on the bioimpedance phase angle remain unclear. We aimed to examine the longitudinal association between objectively measured physical activity and bioimpedance phase angle among community-dwelling older adults.

This community-based cohort study enrolled individuals aged 65 years or older without any disability in the basic activities of daily living. The exposure was physical activity level measured objectively using a tri-axial accelerometer at baseline. The outcome was a whole body phase angle at 50 kHz obtained from a bioelectrical impedance analyzer at a one-year follow-up. The linear regression model was fitted to estimate the continuous associations of physical activity level and phase angle with adjustment of confounders, including age, sex, body mass index, physical performance, and phase angle at baseline.

The primary analysis included 229 individuals (mean age = 72.6 years [standard deviation = 4.9], 62.9% females). In the multivariable linear regression model, physical activity level at baseline is associated with a greater phase angle at follow-up (mean difference per 1 increase, 0.53° [95%CI, 0.23-0.83]). Subgroup analysis by sex showed similar trends. Restricted cubic spline analysis indicated a linear association between phase angle at follow-up and physical activity level at baseline (p = 0.66 for non-linearity).

Higher physical activity level was associated with greater phase angle at one-year follow-up in a linear dose-response manner, independent of demographics, physical performance, and phase angle at baseline, in community-dwelling older adults.