Vitamin D and walking speed in older adults: Systematic review and meta-analysis

Vitamin D is involved in musculoskeletal health. There is no consensus on a possible association between circulating 25-hydroxyvitamin D (25OHD) concentrations and walking speed, a 'vital sign' in older adults. Our objective was to systematically review and quantitatively assess the association of 25OHD concentration with walking speed. A Medline search was conducted on June 2017, with no limit of date, using the MeSH terms "Vitamin D" OR "Vitamin D Deficiency" combined with "Gait" OR "Gait disorders, Neurologic" OR "Walking speed" OR "Gait velocity". Fixed-effect meta-analyses were performed to compute: i) mean differences in usual and fast walking speeds and Timed Up and Go test (TUG) between participants with severe vitamin D deficiency (<= 25nmol/L) (SVDD), vitamin D deficiency (<= 50nmol/L) (VDD), vitamin D insufficiency (<= 75nmol/L) (VDI) and normal vitamin D (> 75nmol/L) (NVD); ii) risk of slow walking speed according to vitamin D status. Of the 243 retrieved studies, 22 observational studies (17 cross-sectional, 5 longitudinal) met the selection criteria. The number of participants ranged between 54 and 4100 (0-100% female). Usual walking speed was slower among participants with hypovitaminosis D, with a clinically relevant difference compared with NVD of -0.18 m/s for SVDD, -0.08 m/s for VDD and -0.12 m/s for VDI. We found similar results regarding the fast walking speed (mean differences -0.04 m/s for VDD and VDI compared with NVD) and TUG (mean difference 0.48 m/s for SVDD compared with NVD). A slow usual walking speed was positively associated with SVDD (summary OR = 2.17[95%CI:1.52-3.10]), VDD (OR = 1.38[95%CI:1.01-1.89]) and VDI (OR = 1.38[95%C1:1.04-1.83]), using NVD as the reference. In conclusion, this meta-analysis provides robust evidence that 25OHD concentrations are positively associated with walking speed among adults.