The association of vitamin D supplementation and serum vitamin D levels with physical activity in older adults: Results from a randomized trial

Abstract

AbstractBackgroundTo assess whether vitamin D3 supplementation attenuates the decline in daily physical activity in low‐functioning adults at risk for falls.MethodsSecondary data analyses of STURDY (Study to Understand Fall Reduction and Vitamin D in You), a response‐adaptive randomized clinical trial. Participants included 571 adults aged 70 years and older with baseline serum 25(OH)D levels of 10–29 ng/mL and elevated fall risk, who wore a wrist accelerometer at baseline and at least one follow‐up visit and were randomized to receive: 200 IU/day (control), 1000, 2000, or 4000 IU/day of vitamin D3. Objective physical activity quantities and patterns (total daily activity counts, active minutes/day, and activity fragmentation) were measured for 7‐days, 24‐h/day, in the free‐living environment using the Actigraph GT9x over up to 24‐months of follow‐up.ResultsIn adjusted models, physical activity quantities declined (p < 0.001) and became more fragmented, or “broken up”, (p = 0.017) over time. Supplementation with vitamin D3 did not attenuate this decline. Changes in physical activity were more rapid among those with baseline serum 25(OH)D <20 ng/mL compared to those with baseline 25(OH)D levels of 20–29 ng/mL (time*baseline 25(OH)D, p < 0.05).ConclusionIn low‐functioning older adults with serum 25(OH)D levels 10–29 ng/mL, vitamin D3 supplementation of 1000 IU/day or higher did not attenuate declines in physical activity compared with 200 IU/day. Those with baseline 25(OH)D <20 ng/mL showed accelerated declines in physical activity. Alternative interventions to supplementation are needed to curb declines in physical activity in older adults with low serum 25(OH)D.