Prenatal risk factors of wheezing at the age of four years in Tanzania

Background-A study was undertaken to assess the interactions between prenat al exposures, early life infections, atopic predisposition, and allergen ex posures in the development of wheezing up to the age of 4 years in a tropic al region of Africa. Methods-The study subjects comprised children born at the district hospital in Ifakara, Tanzania during a 1 year period who were participating in a tr ial of iron supplementation and malaria chemoprophylaxis during the first y ear of life and followed for up to 4 years. From this group of subjects, 65 8 (79%) participated in the interview at 18 months and 528 (64%) in a secon d interview at 4 years. Wheezing was measured with the ISAAC questionnaire. A hospital based inpatient and outpatient surveillance system was set up t o document all attendance by study children for any cause, including episod es of clinical malaria and lower respiratory tract infections. Total IgE le vels and malaria parasites were measured in maternal and cord blood. Total IgE was also measured at 18 months of age. Indoor environmental levels of D er p I and Fel d I were determined using an enzyme linked immunosorbent ass ay at the same time as the interview at the age of 18 months. Results-The prevalence of wheezing at 4 years is common in Ifakara (14%, ra nge 13-15%). The presence of malaria parasites in cord blood (odds ratio, O R = 6.84, 95% CI 1.84 to 24.0) and maternal asthma (OR = 8.47, 95% CI 2.72 to 26.2) were positively associated with wheezing at the age of 4 years, an d cord blood total IgE was negatively associated (OR = 0.24, 95% CI 0.07 to 0.85) tall p<0.05). Parasitaemia at birth was not related to total IgE lev els in cord blood (p=0.6). Clinical episodes of malaria during infancy were not associated with wheezing, and nor were levels of indoor aeroallergens. Conclusion-These findings suggest that events occurring during pregnancy ma y play a role in the future appearance of wheezing, although the results mu st be interpreted with caution because of the small numbers studied.