Background-The causes of the worldwide increases in asthma and allergic diseases in childhood, which seem to relate to increasing prosperity, are unknown. We have previously hypothesised that a reduction in the antioxidant component of the diet is an important factor. An investigation was undertaken of dietary and other risk factors for asthma in Saudi Arabia where major lifestyle diVerences and prevalences of allergic disease are found in diVerent communities. Methods-From a cross sectional study of 1444 children with a mean age of 12 (SD 1) years in Jeddah and a group of rural Saudi villages, we selected 114 cases with a history of asthma and wheeze in the last 12 months and 202 controls who had never complained of wheeze or asthma, as recorded on the ISAAC questionnaire. Risk factors for asthma and allergies (family history, social class, infections, immunisations, family size, and diet) were ascertained by questionnaire. Atopy was assessed by skin prick testing. Results-In univariate analyses, family history, atopy, and eating at fast food outlets were significant risk factors for wheezy illness, as were the lowest intakes of milk and vegetables and of fibre, vitamin E, calcium, magnesium, sodium, and potassium. These diVerences were present also in the urban children considered separately. Sex, family size, social class, infections, and parental smoking showed no relationship to risk. In multiple logistic regression analysis, urban residence, positive skin tests, family history of allergic disease, and the lowest intakes of vitamin E, magnesium and sodium related significantly and independently to risk. The lowest tertile of intake of vitamin E was associated with a threefold (95% CI 1.38 to 6.50) increase in risk when adjusted for the other factors. Intake of milk and vegetables both showed inverse linear relationships to being a case. Conclusions-This study suggests that dietary factors during childhood are an important influence in determining the expression of wheezy illness, after allowing for urban/rural residence, sex, family history, and atopy. The findings are consistent with previous studies in adults and with the hypothesis that change in diet has been a determinant of the worldwide increases in asthma and allergies. (Thorax 2000;55:775-779)

The aim of this study was to contrast the prevalence of allergic symptoms in children living in urban and rural areas of Saudi Arabia and to investigate factors associated with any differences found. A cross-sectional questionnaire survey was conducted of a social class-stratified sample of 1,020 urban and 424 rural 12 yr old children, recording symptoms of current and past allergic disease and doctors' diagnoses, together with nationality and the fathers' educational level and occupations. A significantly greater prevalence of allergic symptoms was found in urban than in rural children and in Saudi than in non-Saudi Arab children. Males were more likely to have some respiratory symptoms and females had more eye and skin symptoms. Educational level and occupation of the father did not influence the likelihood of having symptoms. Logistic regression analyses showed that urban residence and Saudi nationality were the two main risk factors associated with asthmatic symptoms. There is likely to have been a recent increase in the prevalence of allergic disease in Saudi children associated with increased affluence, which has not affected non-Saudi migrants moving into the same environment to the same extent. This is consistent with the hypothesis that the environment, possibly through changes in lifestyle and patterns of infection, influences the expression of allergic disease.

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