Combined impact of healthy lifestyle factors on risk of asthma, rhinoconjunctivitis and eczema in school children: ISAAC phase III

Background Asthma is not the key focus of prevention strategies. A Healthy Lifestyle Index (HLI) was developed to examine the combined effect of modifiable lifestyle factors on asthma, rhinoconjunctivitis and eczema using data from the International Study of Asthma and Allergies in Childhood (ISAAC) phase III. Methods Information on symptoms of asthma, rhinoconjunctivitis, eczema and several lifestyle factors was obtained from children aged 6-7 years through written questionnaires. The HLI combined five lifestyle factors: no parental smoking, child's adherence to Mediterranean diet, child's healthy body mass index, high physical activity and non-sedentary behaviour. The association between the HLI and risk of asthma, rhinoconjunctivitis and eczema was evaluated using multilevel mixed-effects logistic regression models. Findings Data of 70 795 children from 37 centres in 19 countries were analysed. Each additional healthy lifestyle factor was associated with a reduced risk of current wheeze (OR 0.87, 95% CI 0.84 to 0.89), asthma ever (OR 0.89, 95% CI 0.87 to 0.92), current symptoms of rhinoconjunctivitis (OR 0.95, 95% CI 0.92 to 0.97) and current symptoms of eczema (OR 0.92, 95% CI 0.92 to 0.98). Theoretically, if associations were causal, a combination of four or five healthy lifestyle factors would result into a reduction up to 16% of asthma cases (ranging from 2.7% to 26.3 % according to region of the world). Conclusions These findings should be interpreted with caution given the limitations to infer causality from cross-sectional observational data. Efficacy of interventions to improve multiple modifiable lifestyle factors to reduce the burden asthma and allergy in childhood should be assessed

Birthweight and the risk of atopic diseases:The ISAAC Phase III study

Background: The association between birthweight and asthma, eczema and rhinoconjunctivitis is conflicting. Aims: To examine the association between birthweight and symptoms of asthma, eczema and rhinoconjunctivitis. Methods: Parents or guardians of children aged 6-7 yr completed written questionnaires about symptoms of asthma, rhinoconjunctivitis and eczema, and several risk factors, including birthweight. Results: There were 162,324 children from 60 centres in 26 countries. Low birthweight (&lt;2.5 kg) was associated with an increased risk of symptoms of asthma (current wheeze odds ratio = 1.20; 95% confidence interval = 1.12-1.30). Low birthweight was associated with a lower risk of eczema ever. Low birthweight was not associated with rhinoconjunctivitis. Large babies (birthweight ≥4.5 kg) were not associated with any of these outcomes. Conclusions: This study has confirmed that low birthweight is a risk factor for symptoms of asthma, but not for rhinoconjunctivitis. The findings for eczema are equivocal.</p

The impact of the method of consent on response rates in the ISAAC time trends study

BACKGROUND: Centres in Phases I and III of the International Study of Asthma and Allergies in Childhood (ISAAC) programme used the method of consent (passive or active) required by local ethics committees. METHODS: Retrospectively, relationships between achieved response rates and method of consent for 13-14 and 6-7-year-olds (adolescents and children, respectively), were examined between phases and between English and non-English language centres. RESULTS: Information was obtained for 113 of 115 centres for adolescents and 72/72 centres for children. Both age groups: most centres using passive consent achieved high response rates (>80% adolescents and >70% children). English language centres using active consent showed a larger decrease in response rate. Adolescents: seven centres changed from passive consent in Phase I to active consent in Phase III (median decrease of 13%), with five centres showing lower response rates (as low as 34%). Children: no centre changed consent method between phases. Centres using active consent had lower median response rates (lowest response rate 45%). CONCLUSION: The requirement for active consent for population school-based questionnaire studies can impact negatively on response rates, particularly English language centres, thus adversely affecting the validity of the data. Ethics committees need to consider this issue carefully. © 2010 The Union