Serum 25-hydroxyvitamin D3 and the risk of pneumonia in an ageing general population.

Vitamin D has been suggested to have a role in infection defence and on the immune system. We therefore investigated the effect of serum 25-hydroxyvitamin D₃ (25(OH)D₃) on the risk of incident hospitalised pneumonia in an ageing general population in eastern Finland. The study population included 723 men and 698 women aged 53-73 years from the prospective population-based Kuopio Ischemic Heart Disease Risk Factor study who were free of pneumonia, other pulmonary diseases and cancer at baseline in 1998-2001. Incident pneumonia episodes leading to hospitalisation were collected by record linkage to the hospital discharge register. The serum vitamin D status was assayed as 25(OH)D₃ concentration. Cox proportional hazards regression models were used to analyse the effect of serum 25(OH)D₃ on the risk of incident pneumonia. The mean (SD) serum 25(OH)D₃ concentration of the study population was 43.5 (17.8) nmol/l. 73 subjects had at least one hospitalisation episode due to pneumonia during an average follow-up of 9.8 years. After multivariable adjustments, the subjects in the lowest serum 25(OH)D₃ tertile had a 2.6-fold (95% CI 1.4 to 5.0, p trend across tertiles=0.005) higher risk of developing pneumonia compared with the subjects in the highest tertile. This significant result remained even after adjustment for the determinants of serum 25-hydroxyvitamin D₃. These data suggest an inverse effect of serum 25(OH)D₃ concentration on the risk of incident pneumonia in the general ageing population.