Gender-dependent Association of Body Mass Index and Waist Circumference with Disability in the Chinese Oldest Old

OBJECTIVES: To explore associations of body mass index (BMI) and waist circumference (WC) with disability among the Chinese oldest old. DESIGN AND METHODS: 5495 oldest old in the sixth wave of Chinese Longitudinal Healthy Longevity Study conducted in 2011 were included in this study. Disability was assessed by Activities of Daily Living (ADL); height and weight for BMI and WC were measured; information including socio-demographics, lifestyles and health status was collected. RESULTS: Generalized additive models analysis showed that the association of BMI/WC with ADL disability was non-linear. Among the males, logistic regression results supported a ‘J‘ shape association between ADL disability with BMI/WC--the highest tertile group in BMI or WC was significantly associated with an increased risk of ADL disability: odds ratio 1.78 (95% confidence interval (CI): 1.26-2.52) for BMI and 2.01 (95% CI: 1.44-2.82) for WC. Among females, an inverse ‘J’ shape association was found, only the lowest tertile group before the cutoff point had an increased risk of ADL disability: odds ratio 1.42 (95%CI: 1.02-1.97) for BMI and 1.47 (95% CI:1.06-2.04) for WC. CONCLUSIONS: Associations of BMI and WC with ADL disability are significant even in the oldest old, but differ between the genders.