Risk Factors for Chronic Obstructive Pulmonary Disease in a European Cohort of Young Adults

Rationale: Few studies have investigated the factors associated with the early inception of chronic obstructive pulmonary disease (COPD). Objectives: We investigated COPD risk factors in an international cohort of young adults using different spirometric definitions of the disease. Methods. We studied 4,636 subjects without asthma who had prebronchodilator FEV1/FVC measured in the European Community Respiratory Health Survey both in 1991 to 1993 (when they were 20-44 yr old) and in 1999 to 2002. COPD was defined according to the Global Initiative for Chronic Obstructive Lung Disease fixed cut-off criterion (FEV1/FVC < 0.70), and two criteria based on the Quanjer and LuftiBus reference equations (FEV1/FVC less than lower limit of normal). COPD determinants were studied using two-level Poisson regression models. Measurements and Main Results: COPD incidence ranged from 1.85 (lower limit of normal [Quanjer]) to 2.88 (Global Initiative for Chronic Obstructive Lung Disease) cases/1,000/yr. Although about half of the cases had smoked less than 20 pack-years, smoking was the main risk factor for COPD, and it accounted for 29 to 39% of the new cases during the follow-up. Airway hyperresponsiveness was the second strongest risk factor (15-17% of new cases). Other determinants were respiratory infections in childhood and a family history of asthma, whereas the role of sex, age, and of being underweight largely depended on the definition of COPD used. Conclusions: COPD may start early in life. Smoking prevention should be given the highest priority to reduce COPD occurrence. Airway hyperresponsiveness, a family history of asthma, and respiratory infections in childhood are other important determinants of COPD. We suggest the need for a definition of COPD that is not exclusively based on spirometry.