The population risk attribution associated with chronic airway obstruction from the results of the Canadian Obstructive Lung Disease study

Abstract

Background: COPD is a multifactorial disease. We estimated the attributable risk of chronic airway obstruction (CAO), due to several risk factors.

Methods: We measured pre- and post- bronchodilator spirometry and collected information on risk factors using standardized questionnaires in a population sample of 5176 adults, aged ≥40 years from 9 urban sites in Canada. The prevalence of CAO was defined as a post-bronchodilator one-second forced expiratory volume (FEV1) to forced vital capacity (FVC) ratio < lower limit of normal. We estimated the relative risks (RR) associated with risk factors and computed the local Population Attributable Risks (PAR).

Findings: Mean prevalence of CAO was 10.9% (men) and 11.4% (women). Mean PAR for smoking was 5.33% and 3.77% respectively. The influential risk factors in decreasing rank were age, smoking, a history of asthma, low education levels, hypertension and heart disease, passive smoking, history of childhood hospitalization for severe respiratory disease, exposure to biomass fuel for heating and cooking, a history of tuberculosis, working in a dusty job for ≥10 years, and low body mass index. The risk of CAO attributable to the different risk factors varied across sites. All risk factors collectively accounted for 89% and 79.5% of CAO in men and women respectively.

Interpretation: Age and smoking remain dominant risk factors for CAO but other risk factors are also important, which can explain the majority of CAO in this population.