Risk of childhood asthma in a tropical African urban setting: a case - control study at The Aga Khan Hospital, Dar-es-Salaam, Tanzania

Objective: To determine the modifiable and non-modifiable risk factors for childhood asthma in children aged between two and 15years in a tropical urban East-African setting. Methods: Hospital based case-control study matched for age + two months and sex. Data were obtained from parents of cases and controls using a structured interviewer-administered questionnaire. The study sample consisted of 226 cases of two to 15years old, with physician-confirmed asthma, who met a set of defined clinical criteria and 226 controls with no previous diagnosis or symptoms of asthma matched by sex and age (+two months). The Risk Factors included in this study are broadly classified under family history of asthma, race, socio-economic factors, pre and perinatal factors, comorbid history of eczema or worm infestation and indoor environmental pollution. Setting: The outpatient paediatric clinic at Aga Khan Hospital, a secondary care hospital in Dar Es Salaam, Tanzania between July 2012 and January 2013. Results: Of the modifiable risk factors for asthma in this study, maternal smoking during pregnancy yielded an infinite Crude Odds Ratio P = 0.0207. Maternal diet rich in fish and other seafood during pregnancy showed a protective association with asthma (Adjusted Odds Ratio- 0.60; 95% confidence intervals 0.37 – 0.99, P =0.044). A diet rich in milk and dairy products during pregnancy was protective in children older than five years. (Adjusted Odds Ratio - 0.63, 95% confidence intervals 0.38- 1.06, P = 0.024). Family history of asthma is an important non-modifiable asthma risk factor; Paternal Asthma - Adjusted Odds Ratio of 3.14; Confidence Interval 1.49 -6.63, P=0.03), Maternal Asthma - Adjusted Odds Ratio 2.63; 95%Confidence Interval 1.34 – 5.15, P = 0.005and sibling asthma -Adjusted Odds Ratio 2.57; 95%Confidence Interval 1.60 – 4.14, P \u3c 0.0001. Conclusion: Family history of asthma is strongly associated with asthma. Maternal diet during pregnancy is an important modifiable asthma risk factor in the tropical African setting with fish and sea-foods being protective. Further research in a more powered study is required to determine the role of maternal diet rich in milk and dairy products