Urban-rural differences in questionnaire-derived markers of asthma in Kenyan school children.

Grade 4 Kenyan children attending 10 randomly selected public primary schools in Nairobi (urban) and the Muranga District (rural) were surveyed to establish the prevalence of symptom markers of asthma and to assess the impact of urbanization. A respiratory health and home environment questionnaire was administered at school to parents or guardians. The questionnaire response rates were 94.2% (568/ 603) for Nairobi and 89.6% (604/674) for Muranga. The prevalence rates for asthma, defined as "attacks of shortness of breath with wheeze", were 9.5% for urban and 3.0% for rural children (odds ratio (OR) urban versus rural: 3.42; 95% confidence interval (CI): -1.96-5.91). This urban-rural gradient persisted after adjusting for urban-rural differences in host factors (including duration of breastfeeding and family history of asthma and/or allergy), but was largely explained by urban-rural differences in environmental factors, including indoor animals, sharing a bedroom with a smoker, parental education, house ventilation and exposure to motor vehicle fumes en route to school (adjusted OR: 1.59; 95% CI: 0.70-3.55). Similar results were obtained for all other symptoms. These findings confirm the clinical impression that asthma is an important illness in Kenya and underline the need for the further study of environmental factors amenable to intervention, particularly in urban areas.

Prevalence of exercise induced bronchospasm in Kenyan school children: an urban-rural comparison.

BACKGROUND: Higher rates of exercise induced bronchospasm (EIB) have been reported for urban than for rural African schoolchildren. The change from a traditional to a westernized lifestyle has been implicated. This study was undertaken to examine the impact of various features of urban living on the prevalence of EIB in Kenyan school children. METHODS: A total of 1226 children aged 8-17 years attending grade 4 at five randomly selected schools in Nairobi (urban) and five in Muranga district (rural) underwent an exercise challenge test. A respiratory health and home environment questionnaire was also administered to parents/guardians. This report is limited to 1071 children aged < or = 12 years. Prevalence rates of EIB for the two areas were compared and the differences analysed to model the respective contributions of personal characteristics, host and environmental factors implicated in childhood asthma. RESULTS: A fall in forced expiratory volume in one second (FEV1) after exercise of > or = 10% occurred in 22.9% of urban children and 13.2% of rural children (OR 1.96, 95% CI 1.41 to 2.71). The OR decreased to 1.65 (95% CI 1.10 to 2.47) after accounting for age, sex, and host factors (a family history of asthma and breast feeding for less than six months), and to 1.21 (95% CI 0.69 to 2.11) after further adjustment for environmental factors (parental education, use of biomass fuel and kerosene for cooking, and exposure to motor vehicle fumes). CONCLUSIONS: The EIB rates in this study are higher than any other reported for African children, even using more rigorous criteria for EIB. The study findings support a view which is gaining increasing credence that the increase in prevalence of childhood asthma associated with urbanisation is the consequence of various harmful environmental exposures acting on increasingly susceptible populations.

Exercise-induced bronchospasm: a pilot survey in Nairobi school children.

Exercise-induced bronchospasm (EIB), a common feature of asthma in children, has been used as the outcome measure in community-based surveys of childhood asthma to circumvent difficulties arising from relative lack of objectivity in the use of questionnaires in communities with different cultural and language orientations. We report here the results of the first community-based study of childhood asthma in Kenya using EIB as the outcome measurement. The data was collected in a pilot study to develop methodology for a larger subsequent study. The survey targeted grade four children in five Nairobi City Council school each representing a neighbourhood social economic status (SES). Out of 597 eligible, 408 children took part in the study (68% participation rate). EIB defined as decline in FEV1 of 15% or more, post-exercise was found in 10.5% (95% CI; 10.3, 10.7) of the children studied, the highest rate reported so far in Africa. While boys were more likely to exhibit EIB compared to girls, the prevalence of EIB tended to decrease with age, especially among children residing in low SES neighbourhoods where the EIB prevalence rates tended to be lower compared to those among children from higher SES neighbourhoods. However, none of these differences was statistically significant. This study confirms the feasibility of undertaking exercise challenge tests in the African context and we recommend that additional studies of similar nature be carried out in other populations of Africa to explore the potential of using an exercise test as a marker of asthma in epidemiologic studies.