Background: The relationship between body mass index (BMI) and disability-free survival (DFS) remains unclear. Methods: We conducted a 10-year prospective cohort study of 12,666 Japanese individuals aged ≥ 65 y. Information on BMI and lifestyle factors was collected via a questionnaire in 2006. Functional disability data were retrieved from the public Long-term Care Insurance database. Subjects were divided into seven groups according to BMI (<19, 19−21, 21−23, 23−25, 25−27, 27−29 and ≥29). Fiftieth percentile differences (PDs) and 95% confidence intervals (CIs) in the DFS period (differences of period until the first 50% of the composite outcome (disability or death) occurred in each of the BMI groups) were calculated using the Laplace regression model. Results: There was a U-shaped relationship between BMI and the risk of incident composite outcome, with a BMI nadir of 25−27. Based on BMI 25−27 as a reference, the 50th PDs (95% CIs) (in months) in age at disability or death (median DFS) were −20.8 (−26.4, −15.2) (P < 0.001) months for BMI <19, −13.5 (−18.2, −8.7) (P < 0.001) months for BMI 19−21, −9.8 (−14.2, −5.4) (P < 0.001) months for BMI 21−23, −2.9 (−7.5, 1.7) (P = 0.21) months for BMI 23−25, −2.7 (−8.4, 2.9) (P = 0.34) months for BMI 27−29, and −11.5 (−19.6, −3.5) (P = 0.005) months for BMI ≥ 29. These relationships did not differ by sex. Conclusion: Older individuals with a BMI of <23 or ≥29 have a significantly shorter DFS period than those with a BMI of 25−27. It is suggested that the optimal BMI range for maximization of disability-free life expectancy in the elderly population is 23−29.
ASJC Scopus subject areas
- Medicine (miscellaneous)
- Endocrinology, Diabetes and Metabolism
- Nutrition and Dietetics