Background: Acute lower respiratory tract infection (ALRTI) is the leading cause of childhood deaths in most developing countries, including Nigeria. Vitamin D is associated with innate immunity and may play a role in the control of infections. Case-control studies, including a small study from Nigeria, show inconsistent results for the association between vitamin D status and risk of ALRTI.
Aims: To examine the relationship between vitamin D status and hospitalization for ALRTI in Nigerian children.
Methods: Fifty children aged 2-60 months hospitalised with ALRTI were studied prospectively. ALRTI was diagnosed on the basis of modified WHO criteria. Each patient was matched with controls for age and gender. The controls were enrolled either from children attending well-child clinics or general clinics without evidence of respiratory infection or admitted to the hospital for elective surgery. A structured questionnaire collected data on demography, health, diet, duration of exposure to sunlight and percentage of body surface exposed to sunlight (according to type of clothing) while outdoors, and potential risk factors for ALRTI. Serum 25-hydroxyvitamin D [25(OH)D] concentration was measured using a chemiluminescenceimmuno-assay. The differences between cases and controls in serum 25(OH)D concentrations, association between vitamin D status and ALRTI and risk factors for vitamin D deficiency were assessed.
Results: Mean (SD) 25(OH)D concentrations in patients and controls were similar [61·5 (25·8) vs 63·1 (22·9) nmol/L,P = 0·95].25% of all 100 subjects studied had serum 25(OH)D<50 nmol/L. In a multiple conditional logistic regression model, only lower percentage of body surface area exposed to sunlight was associated with increased risk of ALRTI. The percentage of body surface area exposed to sunlight while outdoors (P = 0·028) and vitamin D supplement use (P = 0·009) were independent determinants of vitamin D deficiency in the overall study population.
Conclusions: ALRTI was not associated with vitamin D status, but was associated with less exposure to sunlight. Exposure to sunlight and vitamin D supplementation contributed to vitamin D status in this population.
Keywords: Children; Lower respiratory infection,; Vitamin D,.