Daily sitting time and past-year falls in Japanese adults: an exploratory cross-sectional analysis

Sedentary behavior is a potentially modifiable risk factor for falls, yet the sitting time threshold linked to elevated fall risk remains unclear, particularly in Asian populations.

This study aimed (1) to examine the association between dichotomized daily sitting time and falls in the past year, and (2) to determine an optimal threshold above which the odds of falls significantly increase.

A cross-sectional survey was conducted in 2022 in two aging Japanese communities. Data were collected from 1,331 adults (mean age 68.3 ± 15.2 years; 52.1% women) via self-administered questionnaires. The exposure was self-reported daily sitting time from the Global Physical Activity Questionnaire, and the outcome was at least one fall in the past year. Receiver operating characteristic (ROC) analysis identified the optimal threshold, and logistic regression estimated odds ratios (ORs).

Among 1,331 adults, 20.2% reported ≥1 fall in the past year. ROC analysis identified 4.08 h/day as the optimal cutoff (AUC = 0.52). In adjusted models, sitting ≥4.08 h/day was associated with higher odds of falls (crude OR = 1.44, 95% CI: 1.09-1.91; adjusted OR = 1.35, 95% CI: 1.01-1.81). Continuous sitting time was also positively associated with falls.

Daily sitting time of about 4 h or more was linked to increased odds of past-year falls, but its discriminatory ability was minimal (AUC ≈ 0.5). Adding measures such as muscle strength and balance may improve prediction, and this cutoff could serve as a population-level marker when combined with other risk indicators.