Vitamin D and Physical Function in Older Adults

Projections from NHANES III indicate that approximately 12,000,000 U.S. adults ≥ 60 years of age have vitamin D insufficiency (serum 25(OH)D < 50 nmol/L). A growing body of evidence suggests that vitamin D status may be important in biologic processes involved in the maintenance of physical function. To test the hypothesis that vitamin D insufficiency is associated with poorer muscle strength and physical performance, we propose to evaluate the role of vitamin D status (serum 25(OH)D) on physical function and falls in the CHS All Stars cohort, a population of advanced age. The specific aims are as follows:

Specific Aim 1. To describe the prevalence and correlates of vitamin D insufficiency in adults of advanced age.

Specific Aim 2. To examine the cross-sectional association between vitamin D status and muscle strength (leg and grip strength), physical performance (3 m/15 ft walk time, repeated chair stands, and standing balance), self-reported physical function (mobility, ADL and IADL disability), and falls.

Specific Aim 3. To examine the longitudinal association between vitamin D status at baseline and incident disability (mobility, ADL and IADL disability) over 3 years of follow-up.

Research Hypotheses: Low vitamin D status (25(OH)D < 50 nmol/L) will be associated with (a) lower levels of muscle strength and physical performance; (b) higher levels of self-reported limitations in physical function and falls; and (c) greater odds of incident disability.