Serum 25-hydroxyvitamin D in relation to disability in activities of daily living, mobility, and objective physical functioning among Chinese older adults

Objectives: Vitamin D deficiency is common among older adults, but its association with physical function is not fully understood. The aim of this study was to investigate the associations between serum 25-hydroxyvitamin D and disability in activities of daily living (ADL), mobility, and objective physical functioning among Chinese older adults. Methods: We used cross-sectional data of 2225 older adults (>= 65 years) who participated in the 2011/2012 main survey of the Chinese Longitudinal Healthy Longevity Survey (CLHLS) and the 2012 biomarker sub-study. Serum levels of 25-hydroxyvitamin D were measured by enzyme immunoassay. Outcomes included ADL disability, mobility disability, and disability in three objective physical examinations (standing-up from a chair, picking-up a book from the floor, and turning-around 360 degrees). Results: The multiple regression models suggested that participants in the serum 25-hydroxyvitamin D deficiency group had higher odds of ADL disability (OR: 4.08; 95% confidence interval (CI): 2.81, 5.92), mobility disability (OR: 1.59; 95% CI: 1.05, 2.41), and disability in standing-up from a chair (OR: 2.43; 95% CI: 1.60, 3.69), picking up a book from the floor (OR: 3.09; 95% CI: 2.07, 4.60), and turning-around 360 degrees (OR: 3.09; 95% CI: 2.07, 4.60). Subgroup analyses revealed that some of the above associations (particularly those with mobility disability and disability in turning-around 360 degrees) were only statistically significant among the oldest-old. Conclusions: Among the oldest-old in China, serum 25-hydroxyvitamin D deficiency was associated with disability in ADL, mobility, and objective physical functioning, highlighting the importance of managing the serum 25-hydroxyvitamin D level to promote healthy aging.