Background: Residents of nursing homes may have low 25-hydroxyvitamin D (25OHD) concentrations. Associations between vitamin D and cognitive performance, dementia and susceptibility to infections are not clearly established. The aim of this study was to investigate the prevalence of vitamin D deficiency and to identify associated factors among residents of nursing homes for elderly.
Methods: In this cross-sectional study blood samples for analysis of 25OHD were collected from all participating residents of Swedish nursing homes for the elderly from January to March 2012.
Exclusion criteria: dementia too severe to collect a blood test, terminally ill or refusing participation.
Outcome measures: Serum 25OHD concentrations. Logistic regression to evaluate factors associated with vitamin D deficiency (25OHD < 25 nmol/L).
Results: Blood samples were obtained from 545 of 901 residents of 22 nursing homes. Mean age 86 years (SD 6.9), 68% were women. Prevalence of vitamin D supplementation 17%, dementia 55%, lack of appetite ≥3 months 45% and any antibiotic treatment during the last 6 months 30%. Serum 25OHD concentrations: mean 34 nmol/L (SD 21, median 27, range 4-125), 82% (448/545) had 25OHD < 50 nmol/L and 41% (224/545) had 25OHD < 25 nmol/L. Adjusted OR (95% CI; p-value) for possible predictors of vitamin D deficiency (25OHD < 25 nmol/L): vitamin D supplementation 0.075 (0.031-0.18; p < 0.001), lack of appetite ≥3 months 0.75 (0.50-1.1; p = 0.15), hours outdoors/week 0.99 (0.96-1.0; p = 0.62), Fitzpatrick skin phototype (4-6) 0.69 (0.44-1.1; p = 0.12); dementia 2.3 (1.5-3.4; p < 0.001) and antibiotics last 6 months 1.6 (1.1-2.6; p < 0.029), adjusted for age and gender.
Conclusions: Vitamin D deficiency was common among nursing home residents and strongly associated with dementia. Regardless of causality or not, it is important to be alert for vitamin D deficiency in nursing homes residents with dementia. As expected vitamin D supplementation was associated with less vitamin D deficiency, however lack of appetite, staying outdoors and skin phototype were not significant predictors. Antibiotic treatments during the last 6 months were associated with vitamin D deficiency, potentially supporting the hypothesis that vitamin D deficiency is associated with infections.
Keywords: Antibiotics; Dementia; Frail elderly; Homes for the aged; Infectious disease; Nursing homes; Vitamin D.