Geriatrics & Gerontology International · Apr 2026

Low Body Mass Index Increases Frailty Risk in Old-Old Adults: Findings From a 3-Year Longitudinal Study

By Tabira K, Shiratsuchi D, Miyake Y et al.

OBJECTIVES: Frailty risk increases with age. It is important to understand how body mass index (BMI) relates to changes in frailty risk among adults aged 75 years and older (old-old adults). We examined the longitudinal association between baseline BMI and changes in frailty risk over 3 years. METHODS: This 3-year retrospective cohort study included 515 old-old adults (median age 79.3 years; 45.0% male) who participated in the Latter-Stage Older Persons Health Checkup in Amami City, Japan. Participants were categorized into three BMI groups: < 21.5, 21.5-24.9, and ≥ 25.0 kg/m². Frailty risk was assessed using the Old-Old Questionnaire for Medical Checkups, a validated tool for assessing multidimensional frailty. Thirteen items were analyzed, excluding smoking and social support domains, to better examine the association between BMI and frailty risk. Higher scores indicate a greater frailty risk. We used linear mixed-effects models to analyze the associations between BMI categories at baseline and changes in frailty risk. RESULTS: The BMI < 21.5 kg/m² group participants reported a greater annual increase in frailty risk compared with those in the BMI 21.5-24.9 kg/m² group (β = 0.17, Standard error = 0.07, p = 0.014). The BMI ≥ 25.0 kg/m² group participants reported no significant change in frailty risk compared with those in the BMI 21.5-24.9 kg/m² group (β = -0.01, Standard error = 0.06, p = 0.821). CONCLUSION: Old-old adults with a BMI of ≤ 21.5 kg/m² experienced a more pronounced increase in frailty risk over the 3-year follow-up period.

doi.org/10.1111/ggi.70474Open accessPubMed 41932860Populations