Dietary patterns and risk of asthma: results from three countries in European Community Respiratory Health Survey-II.

Dietary patterns offer an alternative to the analysis of individual foods or nutrients in nutritional epidemiological studies. The aim of the present study was to identify dietary patterns common to different European countries and examine their associations with asthma. In five study centres (two in Germany, two in the UK and one in Norway), 1174 adults aged 29-55 years completed a FFQ and respiratory symptoms questionnaire. A meta-analytic approach was used to identify the dietary patterns and analyse them in relation to current asthma, asthma symptoms and bronchial responsiveness (BHR). Two patterns emerged, generally correlating with the same foods at different centres: one associated with intake of meats and potatoes; the other with fish, fruits and vegetables. There was no evidence that the fish, fruits and vegetables pattern was associated with asthma (OR 1.11 (95 % CI 0.93, 1.33)), symptom score (ratio of means 1.07 (0.98, 1.17)) or BHR (regression coefficient - 0.01 ( - 0.12, 0.10)), though these CI appeared to rule out large protective effects of consuming these foods. There was no overall evidence that the meat and potato pattern was associated with asthma (OR 1.02 (0.79, 1.31)), symptom score (ratio of means 1.07 (0.84, 1.36)) or BHR (regression coefficient - 0.08 ( - 0.27, 0.10)), but there was heterogeneity between centres in the association with symptom score: a negative association at the two German centres; a positive association at the others. Heterogeneity in a multi-centre observational study of diet could suggest alternative explanations for apparent effects of diet, such as uncontrolled confounding.