Relationships of active smoking to asthma and asthma severity in the EGEA study

The role of smoking as potential risk factor, selection factor ("healthy sm oker" effect) and modifying factor (severity) of asthma was studied in the Epidemiological study on the Genetics and Environment of Asthma, bronchial hyperresponsiveness and atopy (EGEA). The analysis involved 200 adult asthmatic cases recruited in chest clinics, 265 nonasthmatic controls and 586 relatives of asthmatics (147 with asthma ). Asthma in childhood was not associated with a reduced take-up of smoking (o dds ratio (OR)=1,06 in males and 0.98 in females), but smoker asthmatic cas es quit more often than controls (OR = 2.20 (95% confidence interval (95% C I) 1.11-4.34) in males and 2.76 (1.19-6.42) in females). Adult onset asthma was unrelated to ever smoking (OR 1.07 in males and 1.02 in females). In a sthmatic cases, active smoking was associated with asthma severity. Current smokers, compared to never and exsmokers, had more asthma symptoms, more f requent (greater than or equal to 1 attack.day(-1)) asthma attacks (OR 2.39 (95% CI 1.06-5.36)) and higher asthma severity scores. No clear pattern re garding the relationships of smoking habits with asthma was observed in fir st degree relatives. It is concluded that active smoking is not a risk factor for asthma in adul thood, but that smoking increases asthma severity.