Prevalence, risk factors and comorbidities of COPD among never-smokers

Abstract: The overall aim of this thesis was to investigate prevalence, risk factors and comorbidity of COPD among never-smokers. COPD was in this thesis defined as a syndrome also including prior asthma diagnosis with chronic airway obstruction. In papers I-III population-based cohorts of the Obstructive Lung Disease in Northern Sweden (OLIN) studies were used. In paper IV data from the OLIN studies was pooled with data from the West Sweden Asthma study. Prevalence of COPD among never-smokers was 3.0-7.7% depending on spirometric definition, and similar in 1994-1996 vs. 2009-2012. Corresponding prevalence of GOLD ≥2 was 1.3-3.5%. Symptoms were highly prevalent in subjects with GOLD ≥2, regardless of smoking status. No significant regional differences in prevalence between OLIN and WSAS were seen. Risk factors for COPD among never-smokers included age, physician-diagnosed asthma and occupational exposure to gas, dust or fumes. Passive smoking in multiple settings was independently associated with an incrementally increased risk of COPD. Comorbidities, in particular cardiac and cardiovascular conditions, were highly prevalent among subjects with GOLD ≥2 regardless of smoking status. In conclusion, COPD is a common condition among never-smokers, and associated with previous asthma and exposures including passive smoking and occupational gas, dust or fumes. Never-smoking subjects with COPD had significantly more respiratory symptoms and comorbidities than never-smokers without COPD. Comorbidities are highly prevalent in COPD regardless of smoking history.