Life-course of atopy and allergy-related disease events in tropical sub-Saharan Africa: a birth cohort study
In high-income countries, allergy related-diseases (ARDs) follow a typical sequence, the “Atopic March”. Little is known about the life-course of ARDs in the markedly different, low-income, tropical environment. We describe ARDs in a tropical, African birth cohort.
Ugandan children were followed from birth to nine years. ISAAC questionnaires were completed at intervals; doctor-diagnosed ARDs were recorded throughout follow-up. Skin prick tests (SPTs) were done at three and nine years. Atopy was defined as ≥1 positive SPT.
Of 2345 live-born children, 1214 (52%) were seen at nine years. Wheeze and eczema were common in infancy but by nine years only 4% reported recent wheeze, 5% eczema and 5% rhinitis. Between three and nine years, atopy prevalence increased from 19% to 25%. Atopy at three or nine years was associated with reported ARD events at nine years, for example OR=5.2 (95% CI 2.9-10.7) for atopy and recent wheeze at nine years. Reported or doctor-diagnosed ARD events in early childhood were associated with the same events in later childhood, for example OR=4.4 (2.3-8.4) for the association between reported wheeze before three years with reported recent wheeze at nine years, but progression from early eczema to later rhinitis or asthma was not observed.
Allergen sensitisation started early in childhood and increased with age. Eczema and wheeze were common in infancy and declined with age. Atopy was strongly associated with ARD among the few affected children. The typical Atopic March did not occur. Environmental exposures during childhood may dissociate atopy and ARD.