Comparison of the prevalence of reversible airways obstruction in rural and urban Zimbabwean children.

Abstract

The prevalence of reversible airways obstruction has been assessed in children in three areas in Zimbabwe-northern Harare (high socioeconomic class urban children), southern Harare (low socioeconomic class urban children), and Wedza Communal Land (rural children from peasant families). Peak expiratory flow (PEF) was measured before and after six minutes' free running in 2055 Zimbabwean primary school children aged 7-9 years. Height and weight were measured and nutritional state expressed as a percentage of the 50th centile for age (Tanner-Whitehouse standards). Reversible airways obstruction was deemed to be present when peak expiratory flow was below the 2-5th centile for height before exercise and rose by more than 15% after inhalation of salbutamol and when it fell by 15% or more after exercise and rose again after salbutamol. The prevalence of reversible airways obstruction was 5-8% (95% confidence interval 4-1-7-5%) in northern Harare (n = 726); 3-1% (1P8-45%) in southern Harare (n = 642), and 0-1% (0-0-0-4%) in Wedza (n = 687). In northern Harare, the only study area in which white children were found, the prevalence of reversible airways obstruction was similar in white (5-3%, 10/188) and black (5 9%, 32/538) children. Indicators of nutritional state also showed no significant differences between white and black children in northern Harare but were lower in southern Harare and lower still in Wedza. Urban living and higher material standards of living appear to be associated with a higher prevalence of reversible airways obstruction in children in Zimbabwe.Childhood asthma is an extremely common problem in industrialised countries and there is evidence that the prevalence may have increased in the last 20 years.`15 Studies from the developing world have shown large variations in asthma prevalence in genetically similar populations living in different environments.' Both lines of evidence suggest that the major determinants of asthma prevalence in any particular population are environmental. Knowledge of different prevalence rates in differing environments should help to guide the design of further studies in an attempt to identify which factors in the environment are relevant to the development of asthma in genetically predisposed individuals.The epidemiological study of asthma is beset by problems of definition,9 and comparison of the results of the various studies is made difficult by differences between the methods of data collection. The measurement of change in peak expiratory flow (PEF) in a free running exercise challenge test, however, is a sensitive method of screening for bronchial hyperreactivity in children'0 and can easily be used to screen large numbers of children.7"' Careful adherence to method within a particular study allows confidence in the significance of differences between groups-The study of Van Niekerk and others7 in South Africa showed the prevalence of exercise induced bronchoconstriction in Xhosa children to be 20 times higher in an urban setting than in a rural setting....

Prevalence of asthma-related symptoms and bronchial responsiveness to exercise in children aged 13-14 yrs in Barcelona, Spain

“…Using a similar free running test in children, the prevalence of exercise-induced bronchoconstriction varies from 12% in children aged 12 yrs from New Zealand [25] to 6% in children aged between 7-16 years in Copenhagen [9]. However, an extremely low prevalence of 0.1% has been reported in a rural area of Zimbabwe [26]. Although the presence of such marked variations strongly suggests that the environment influences both asthma and bronchial responsiveness, the influence of genetic factors is also possible at this wide geographical scale.…”

“…Since reduction in PEFR due to fatigue was not studied by BARDAGÍ et al [15], it is not known whether differences in the prevalence of bronchial responsiveness after running between the present study and that of BARDAGÍ et al [15] may be attributed to the previously mentioned fatigue effect. In Zimbabwean children, the prevalence of exerciseinduced bronchoconstriction varied from 5.8% in an urban area with high living standards to 0.1% in a rural district [26]. Different prevalence rates in populations with a similar genetic background are illustrated by studies in Barcelona and Mataró [15].…”

Allergy in Children in Hand Versus Machine Dishwashing

“…It is most likely that the lower prevalence of allergy seen in children from hand dishwashing families is related to lifestyle factors, but lifestyle factors other than dishwashing practices may be important. For example, overcrowded housing, 20 low socioeconomic status, 28,29 and immigration status 30 are all factors that have been associated with reduced allergy levels in various studies, and these factors may also be associated with dishwashing practices. We used multivariate OPLS analyses to screen the data for confounders and covariates, but despite adjusting for such factors in logistic regression models, the associations between hand dishwashing and allergy, and traditional cooking and allergy, remained, implying that a causal relationship might be possible.…”

Pediatric Asthma in Southern Africa

“…The finding of Keeley et al, that the prevalence of BHR was similar in different race groups of the same socio-economic status, questions the race-based conclusions of previous authors [4]. On the other hand, Terblanche et al found that the prevalence of exercise-induced bronchoconstriction was significantly higher among white children living in Cape Town (5.87%) than in coloured children resident there (4.05%).…”