Case-control study of the role of nutritional rickets in the risk of developing pneumonia in Ethiopian children

Background Pneumonia is the most important cause of morbidity and mortality in children aged under 5 years worldwide. Studies in developing countries have suggested an association between nutritional rickets and pneumonia. Since both nutritional rickets and pneumonia are common in Ethiopia, we did a case-control study to determine the role of nutritional rickets in the development of pneumonia. Methods Cases were children younger than 5 years admitted to the Ethio-Swedish Children's Hospital during a 5-year period with a diagnosis of pnuemonia (n=521), but data were incomplete for 21 of these and they were not included. Controls (n=500) were matched for admission within 3 months of cases and age within 3 months and had no evidence of pneumonia. Nutritional, demographic, and clinical and radiographic data for rickets and pneumonia were collected. Matched odd ratios and logistic regression were used to test the significance of the association of richets and pneumonia. Findings Rickets was present in 210 of 500 cases compared with 20 of 500 controls (odds ratio 22.11). There were significant differences between cases and controls for family size, birth order, crowding, and months of exclusive breastfeeding (p<0.05). After correction for these confounding factors by logistic regression, there was still a 13-fold higher incidence of rickets among children with pneumonia than among controls (13.37 [95% CI 8.08-24.22], p<0.001). Interpretation Vitamin D or calcium deficiency may be important predisposing factors for pneumonia in children aged under 5 years in developing countries. Efforts to prevent vitamin D deficiency or calcium supplementation may result in significant reductions in morbidity and mortality from pneumonia in these children.