Season-specific associations between electricity-based frailty risk and life-space mobility, health-related quality of life, and physical function in older adults

Background: Seasonal variations in physical and mental functioning among older adults have been widely reported; however, whether frailty risk exhibits season-specific patterns and associations with health-related outcomes remains unclear. This exploratory study aimed to examine season-specific associations between electricity-based frailty risk and health-related outcomes among community-dwelling older adults.

Methods: Older adults living alone in apartment complexes in Osaka City, Japan were recruited. Monthly frailty risk indices, based on patterns of daily living behaviors such as wake-up time, bedtime, and time spent outside the home, were derived from household electricity consumption data collected over a 12-month period from October 2023 to September 2024. Life-space mobility, health-related quality of life (HRQoL), and physical function were assessed once via a face-to-face survey conducted between October and November 2024 using the Life-Space Assessment (LSA), the EuroQol 5-Dimension 5-Level questionnaire (EQ-5D-5L), and the Timed Up and Go (TUG) test, respectively. Seasonal mean frailty risk indices were classified according to the seasonal definitions provided by the Japan Meteorological Agency. Bayesian correlation and linear regression analyses were conducted separately for each season, and exploratory linear mixed-effects models were performed using the monthly Frailty Risk Index values.

Results: Of the 18 individuals who participated, 14 [median age: 81.0 years, interquartile range (IQR), 10.3 years; 86% women] were included in the analysis. In winter, Bayesian analyses supported negative correlations between the Frailty Risk Index and the LSA [Bayes factor (BF₁₀) =6.285, 95% confidence interval (CI): −0.857 to −0.146] and EQ-5D-5L (BF₁₀ =13.95, 95% CI: −0.885 to −0.237), whereas no sufficient evidence supported an association with physical function assessed by the TUG test. In Bayesian regression analyses, the winter model including both the LSA and EQ-5D-5L showed the highest posterior support (BF_M =2.089, R²=0.603), although this finding should be interpreted cautiously owing to the small sample size. No sufficient evidence of an association was observed in spring, summer, or autumn.

Conclusions: In this exploratory pilot study of 14 older adults living alone, electricity-based frailty risk was associated with life-space mobility and HRQoL, with associations observed for winter Frailty Risk Index values. However, the small sample size, single-time assessment of health-related outcomes, and potential residual confounding preclude definitive conclusions regarding season-specific effects. Larger longitudinal studies with repeated health assessments are needed to validate these findings.