Bacteriuria and vitamin D deficiency: a cross sectional study of 385 nursing home residents

Background: Up to half of elderly people at nursing homes have asymptomatic bacteriuria, and concentrations of 25-hydroxyvitamin D (25OHD) are generally low. Vitamin D is a modulator of the immune system and involved in protection of the epithelium in the urinary tract as well. The objective was to determine a possible association between bacteriuria and vitamin D deficiency among elderly people at nursing homes. Methods: Cross-sectional study: Voided urine specimens and blood samples for cultivation and analysis of 25OHD were collected from elderly people at nursing homes in Sweden. Exclusion criteria were: urinary catheter, ongoing antibiotic treatment, incontinence or dementia too severe to provide a voided urine specimen or leave a blood sample, unwillingness to participate or terminal illness. Urine cultures and serum 25OHD concentrations were outcome measures and the association of bacteriuria with vitamin D deficiency was determined by logistic regression. Results: Twenty-two nursing homes participated and 385 of 901elderly people provided voided urine specimens and blood samples. The mean age was 87 (SD 6.7), 69% women, 19% received vitamin D supplement, 13% had diabetes mellitus, and 54% were diagnosed with dementia. There was significant growth of potentially pathogenic bacteria in 32% (123/385) of voided urine specimens. Escherichia coli were present in 83% of positive urine cultures. The mean concentration of 25OHD in serum was 35 nmol/L (SD 21). Thirty-seven per cent (143/385) had 25OHD < 25 nmol/L, and 3.1% (12/385) 25OHD < 12.5 nmol/L. No association between bacteriuria and 25OHD < 25 nmol/L, OR 1.4 (0.86-2.3; p = 0.18) adjusted for age, gender, diabetes mellitus and dementia was found. However, if using 25OHD < 12.5 nmol/L as a cut-off for vitamin D deficiency the adjusted odds-ratio was 4.4 (1.1-17; p = 0.031). Conclusions: Bacteriuria and vitamin D deficiency was common. No association between bacteriuria and 25OHD < 25 nmol/L was found. If using 25OHD < 12.5 nmol/L as cut-off for vitamin D deficiency there was an association. However, this has to be interpreted with caution as causality cannot be evaluated as well as only few residents had 25OHD < 12.5 nmol/L.