Prevalence of night-time dyspnoea in COPD and its implications for prognosis.
The information on night-time symptoms in chronic obstructive pulmonary disease (COPD) is sparse. We investigated the prevalence of night-time dyspnoea in 6616 individuals with COPD recruited from the general population in the Copenhagen area, Denmark, and described characteristics and prognosis of subjects with this symptom. The prevalence of night-time dyspnoea was 4.3%: 2.1% in Global Initiative for Chronic Obstructive Lung Disease (GOLD) group A, 12.9% in GOLD B, 2.6% in GOLD C and 16.3% in GOLD D. Compared with individuals without night-time dyspnoea, those with night time dyspnoea had lower forced expiratory volume in 1 s, higher daytime dyspnoea scores (modified Medical Research Council scale) and more wheezing, more often had chronic mucus hypersecretion, ischaemic heart disease and atrial fibrillation, and more often reported stress, nervousness and tiredness. After adjustment for age and sex, the presence of night-time dyspnoea was associated with future COPD exacerbations (hazard ratio (HR) 2.3, 95% CI 1.7-3.0), hospital admissions due to COPD (HR 3.2, 95% CI 2.3-4.4) and mortality (HR 1.7, 95% CI 1.2-2.3). Prevalence of night-time dyspnoea in COPD increases with disease severity according to both spirometric and clinical GOLD classification, and is associated with presence of daytime respiratory symptoms and cardiac comorbidities. Night-time dyspnoea is a significant predictor of poor prognosis in individuals with COPD.