Basal Metabolic Rate and 5-Year Risk of Disability in Older Adults: Evidence From a Cohort With Counterfactual Analysis.

OBJECTIVES: Basal metabolic rate (BMR) declines with age and reflects reduced physiological reserve. Estimated BMR, derived from anthropometric variables, may reflect vulnerability related to age, sex, and body size rather than directly measured intrinsic metabolic function. This study examined the association between estimated BMR and 5-year incident disability in community-dwelling older adults and evaluated the impact of small changes in BMR on disability risk. DESIGN: Five-year prospective cohort study. SETTING AND PARTICIPANTS: The study included 13,343 community-dwelling adults aged 65 years or older who were free of disability at baseline. METHODS: BMR was estimated using the revised Harris-Benedict equation and categorized into quartiles. Incident disability was defined as new eligibility for Japan's Long-Term Care Insurance system. Cox proportional hazards models and restricted cubic splines were used to evaluate associations between estimated BMR and disability risk. Counterfactual analysis estimated the hypothetical effect of a 50 kcal/d lower estimated BMR. Multiple imputation was performed, and robustness was examined using multicollinearity assessment, competing risk analysis, proportional hazards testing, and sensitivity analyses excluding participants with stroke or Parkinson's disease. RESULTS: Participants in the lowest estimated BMR quartile had a higher risk of incident disability than those in the highest quartile (hazard ratio, 2.8; 95% CI, 2.4-3.1). Lower estimated BMR was consistently associated with higher disability risk, and robustness analyses showed materially unchanged findings. Counterfactual estimates suggested that a hypothetical 50 kcal/d lower estimated BMR was associated with increased disability risk. CONCLUSIONS AND IMPLICATIONS: Lower estimated BMR was associated with incident disability and may serve as an integrated anthropometric risk marker rather than a direct measure of intrinsic metabolic function. This simple, noninvasive indicator may help identify older adults at elevated risk of functional decline.