Vitamin D status and physical function in nursing home residents: a 1-year observational study

Low vitamin D blood levels are highly prevalent in elderly people, particularly in nursing home residents (NHR). A relation between vitamin D levels and physical function (PF) is described in several studies in older adults; however, data on NHR are scarce and there is presently no information on the time course of vitamin D levels and PF in this population. The aim of the present study was to describe the 25-hydroxyvitamin D [25(OH)D] status of NHR at baseline (t1) and after 1 year (t2) to examine whether 25(OH)D blood levels are related to PF at t1 and at t2, and whether changes in 25(OH)D levels over 1 year are related to changes in PF.

All NHR (≥ 65 years) without tube-feeding and severe acute or end-stage disease were asked to participate. At t1 and t2 fasting blood samples were taken for the analysis of 25(OH)D serum levels and PF was estimated by activities of daily living (Barthel ADL) and measured by handgrip strength (HGS) and timed 'up and go' test (TUG).

In total, 115 residents, aged 87 (82-93) years (all data in median and 1st-3rd quartile), showed the following values for PF: ADL 50 (20-65) points, HGS 40 (30-50) kPa and TUG 26 (18-31) s. Vitamin D deficiency (< 50 nmol/l) was present in 93.9 % (70.4 % < 25 nmol/l) at t1 and in 71.2 % (57.3 % < 25 nmol/l) at t2. At t1 and at t2 a weak correlation between vitamin D level and PF (Spearman's correlation coefficient t1: ADL r = 0.367, HGS r = 0.313; t2: ADL: r = 0.247; all p < 0.01) was observed. There was no correlation between changes in vitamin D levels over 1 year and changes in PF.

Almost all NHR included in the study showed vitamin D deficiency. 25(OH)D levels were weakly correlated to PF at baseline and at follow-up, and an increase in vitamin D levels was not associated with positive effects on PF in this study.