Serum Vitamin D Levels in a Population of Adult Asthmatics in Kinshasa, Democratic Republic of Congo

Background: Vitamin D deficiency is common in general population and is thought to be involved in the natural history of several chronic lung diseases such as asthma. However, the magnitude of the association has not yet been reported in asthmatic adults in Sub-Saharan Africa. The aim of this study was to determine serum vitamin D levels in adult patients with asthma living in Kinshasa. Methods: A sample of 216 subjects reporting asthma were recruited from the University Clinics of Kinshasa and some parishes in Kinshasa. Socio-demographic data were recorded, nutritional status assessed via body mass index (BMI) calculation, FEV1 values obtained, and serum vitamin D levels measured. Serum vitamin D levels were analyzed according to the time spent outdoors in the sun and their correlation with BMI and FEV1. Results: Participants were on average 45.23 years old (SD 17.56) and predominately female (74%). Serum vitamin D levels ranged from 5 to 42 ng/ml, with an average of 20.8 ng/ml (SD 6.1). Vitamin D levels were normal (?30 ng/ml) in ten subjects (4.8%; 95% CI: 1.9-7.7) and abnormal (<30 ng/ml) in 197 subjects (95.2%; 95% CI: 92.0-98.0); of this latter group, 89% (95% CI: 84.6-93.2) were vitamin D insufficient (10-29 ng/ml) and 6% (95% CI: 3.0-9.6) vitamin D deficient (<10 ng/ml).Mean serum vitamin D levels did not differ based on the time spent outdoors in the sun (p = 0.714), and there was no correlation between serum vitamin D and FEV1 (r = 0.018) or BMI (r = 0.033). Conclusions: Vitamin D insufficiency is common in adult asthmatics in Kinshasa but does not appear to be correlated with FEV1 or BMI. Additional population-based surveys are needed to fully assess associations between asthma and vitamin D concentrations for targeted interventions