Rural-urban differences in the association between disability and body mass index among the oldest-old in China

Introduction: The issue of disability prevention is considered as a priority for research in geriatrics in modern society, especially for the oldest-old. There are many evidences certificated that obesity is associated with disability in developed countries. However, few studies pay attention to relationship between them in developing countries. Furthermore, it is also unknown whether the association is similar among the oldest-old in rural and urban areas. The purpose of this study is to explore rural-urban differences in the association between disability and BMI among the oldest-old in China. Methods: 4076 seniors (80+) were included from the 2014 wave of Chinese Longitudinal Healthy Study. Disability, body mass index and other information including socio-demographic variables, health behavior conditions and health status were collected. Logistic regression analysis was employed to examine the association. Results: Of 4076 respondents, 1817 (44.6%) were urban elderly. Overall, 26.6% of the participants had disability, and 31.8% for urban, 22.4% for rural. After controlling for other variables, the significant association between BMI and disability was found for urban oldest seniors, but not for rural ones. Age, living arrangement, Non-communicable disease and annual physical examination were important determinants related to disability. Conclusions: The association between BMI and disability differed according to residence. Both overweight and underweight were red flags of disability among Chines seniors (80+) in urban areas. Therefore, proper weight management is important for preventing disability among urban oldest-old. Additionally, annual physical examination, prevention and control of chronic diseases should be recommended to all of the oldest-old.