Joint effect of obesity and TNFA variability on asthma: two international cohort studies

Obesity is a risk factor for asthma. Adipose tissue expresses pro-inflammatory molecules including tumour necrosis factor (TNF), and levels of TNF are also related to polymorphisms in the TNF-a (TNFA) gene. The current authors examined the joint effect of obesity and TNFA variability on asthma in adults by combining two population-based studies. The European Community Respiratory Health Survey and the Swiss Cohort Study on Air Pollution and Lung and Heart Disease in Adults used comparable protocols, questionnaires and measures of lung function and atopy. DNA samples from 9,167 participants were genotyped for TNFA -308 and lymphotoxin-a (LTA) +252 gene variants. Obesity and TNFA were associated with asthma when mutually adjusting for their independent effects (odds ratio (OR) for obesity 2.4, 95% confidence interval (CI) 1.7–3.2; OR for TNFA -308 polymorphism 1.3, 95% CI 1.1–1.6). The association of obesity with asthma was stronger for subjects carrying the G/A and A/A TNFA -308 genotypes compared with the more common G/G genotype, particularly among nonatopics (OR for G/A and A/A genotypes 6.1, 95% CI 2.5–14.4; OR for G/G genotype 1.7, 95% CI 0.8–3.3). The present findings provide, for the first time, evidence for a complex pattern of interaction between obesity, a pro-inflammatory genetic factor and asthma

Asthmatics and ex-smokers respond early, heavy smokers respond late to mailed surveys in Italy

Response to mailed epidemiological surveys has decreased in recent decades. Since subjects with respiratory symptoms are usually early responders to surveys performed in Southern Europe, this trend could bias prevalence estimates. The present study aimed at evaluating the impact of non-response bias on prevalence estimates of respiratory symptoms and smoking habits. METHODS: In 9 centres, participating in the Italian Study on Asthma in Young Adults (ISAYA), random samples of people aged 20-45 years were administered a mailed questionnaire between 1998 and 2000. Non-responders were contacted again first by mail and then by phone. Cumulative response percentage was 30.5%, 52.4% and 72.7% (18,873/25,969), respectively, after the 1st, 2nd and 3rd contact. RESULTS: The prevalence of self-reported current asthma, asthma-like symptoms, and chronic cough/phlegm was more than halved from the first contact (5.6%, 17.8%, 14.6% respectively) to the third contact (2.7%, 6.4%, 6.9%). This pattern was less pronounced when considering allergic rhinitis and past asthma, whose prevalence decreased, respectively, from 21.5% to 15.6% and from 3.5% to 2.6%. At the same time the proportion of current smokers increased from 29.2% to 38%, while the proportion of ex-smokers decreased from 16.5% to 10.1%. In a multinomial logistic model current asthma, asthma-like symptoms, chronic cough/phlegm and smoking habits, and to a lower extent past asthma and allergic rhinitis, were significant predictors of late response. CONCLUSIONS: In Italy when response percentage is low, the prevalence of current asthma, chronic cough/phlegm and ex-smokers is overestimated, while the proportion of current smokers is underestimated