Association between vitamin D deficiency, low high density lipoprote in cholesterol and higher risk of activities of daily living disability and dementia in Chinese adults aged over 65 years

BACKGROUND: Activities of daily living (ADL) disability and dementia are major contributors to the growing burden of ageing-related public health challenges in China. OBJECTIVE: To evaluate the independent and combined associations of vitamin D deficiency and dyslipidemia, particularly low high-density lipoprotein cholesterol (HDL-C), with ADL disability, dementia, and their composite outcome among Chinese older adults. METHODS: We analyzed data from 2107 community-dwelling Chinese adults aged ≥65 years participating in the 2014 wave of the Chinese Longitudinal Healthy Longevity Survey (CLHLS). Multivariable logistic regression models were used to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: Vitamin D deficiency (<20 ng/mL) was independently associated with higher odds of the composite outcome, ADL disability, and dementia. Low HDL-C (<1.0 mmol/L) was significantly associated with the composite outcome and ADL disability, but inversely associated with dementia. Notably, participants with both vitamin D deficiency and low HDL-C had dramatically elevated risks: OR = 8.27 (95% CI: 3.98-17.20) for the composite outcome and OR = 7.78 (95% CI: 3.74-16.17) for ADL disability. A significant multiplicative interaction between vitamin D and HDL-C was observed for the composite outcome and ADL disability (both P-interaction < 0.001), but not for dementia (P-interaction = 0.591). CONCLUSIONS: Vitamin D deficiency and low HDL-C levels are independently and synergistically associated with increased risk of functional and cognitive impairment in Chinese older adults.