Plasma 25-hydroxyvitamin D level and risk of frailty among Chinese community-based oldest-old: evidence from CLHLS study

Background: Vitamin D deficiency has been linked to risk of frailty. However, there are limited data for evaluating the potential association of Vitamin D with frailty in a longevous (80+) population. The aim of this study was to examine the association between plasma 25-hydroxyvitamin D [25(OH)D] level and risk of frailty among Chinese oldest-old in the communities. Methods: Secondary analysis of data compiled by the 2011 wave of the Chinese Longitudinal Healthy Longevity Survey (n=1324) was extracted. Frailty was assessed by the Study of Osteoporotic Fractures (SOF) index. Multivariate logistic regression and spine smoothing with threshold effect analysis were performed to investigate the association between 25(OH)D level and risk of frailty after adjusting for socio-demographic variables, health characteristics and confounding biomarkers. Results: The mean age was 92.89 ± 7.92 years, and 844(63.7%) of participants were women. In all, 426 (33.2%, 95% confidence interval, CI: 29.66-34.69) frail participants were recorded . After adjustment for confounding covariates, the level of 25(OH)D was significantly related to frailty. By the spline smoothing with threshold effect analysis, a monotonically negative association between 25(OH)D and frailty was identified. Subgroup analyses revealed that the association did not differ by gender and age. Conclusions : 25(OH)D level was inversely associated with the risk of frailty among the Chinese community-based oldest-old.