Asthma and COPD in an Italian adult population: role of BMI considering the smoking habit.

Smoking and body mass index (BMI) are well-documented risk factors that contribute substantially to chronic obstructive pulmonary disease (COPD) and asthma. However, the relations among smoking, obesity, and COPD or asthma remain to be clarified. We conducted a population-based cross-sectional epidemiologic study to explore the association between BMI and COPD or asthma among non-smokers, smokers and ex-smokers using information obtained from the Health Search database (HSD) owned by the Italian College of General Practitioners (SIMG), which stores information on about 1.5% of the total Italian population served by general practitioners (GPs). Our study confirms the importance of smoking status in patients with COPD, but not in those with asthma. Moreover, it demonstrates that the increase in BMI is frequently associated with the diagnosis of COPD or asthma, suggesting that the probability of suffering from COPD or asthma increases with the increase in body weight regardless of the smoking status. The association between an increase in BMI appears to be greater in women than in men. Our data also show that underweight is significantly associated with COPD, but only in men, while being underweight apparently protects from the possibility of suffering from asthma.