Determinants of severe exercise-induced bronchoconstriction in Nigerian children with asthma.

Abstract

Asthmatics with severe exercise-induced bronchoconstriction (EIB) are at high risk of exacerbations. The purpose of this study was to determine the prevalence, phenotypic, and laboratory determinants of severe EIB in Nigerian children with asthma. Children with controlled asthma (n = 101) underwent characterization and free-running exercise bronchoprovocation at a center in Nigeria. Lung function was measured before, then 5, 10, 15, and 30 minutes after 6 to 8 minutes exercise. Severe EIB was defined as ≥50% decrease in forced expired volume in 1 second (FEV1 ) from preexercise. Serum vitamin D and total antioxidant capacity were measured chromatographically. Factors predicting severe EIB were tested by logistic regression. The sample was enriched in children with corticosteroid-naïve, mild intermittent asthma (71%). Thirteen percent had no EIB, 22% had severe and 65% nonsevere EIB. Children with severe EIB had higher preexercise FVC (105% vs 96%; P = .03) and FEV1 (98% vs 90%; P = .07), greater obesity (13.6% vs 1.3%; P = .02), more allergic rhinitis (AR) (63.6% vs 35.4%; P = .03), but less exposure to household pets (31.8% vs 72.2%; P = .003) compared to children with nonsevere EIB. Significant determinants (odds ratios/confidence intervals) for severe EIB were obesity = 12.3 (1.2-125.1), AR = 3.18 (1.19-8.52), blood eosinophilia = 1.005 (1.001-1.009), and hypovitaminosis D = 0.87 (0.81-0.93). In Nigerian children with asthma, severe EIB is common and associated with remediable comorbidities including type 2 pattern inflammation and vitamin D deficiency.