The burden and long-term outcomes of diagnosed and underdiagnosed COPD across diverse communities from high-income, middle-income, and low-income countries: the Prospective Urban Rural Epidemiology (PURE) study.
TL;DR
The high prevalence of underdiagnosed COPD and related poor outcomes suggest that a large burden of COPD is under-recognised and presents missed opportunities for early intervention that can modify disease trajectory and improve long-term health outcomes.
Abstract
Background
Airflow obstruction detected on spirometry is a hallmark of chronic obstructive pulmonary disease (COPD) and is needed for the diagnosis of COPD. Sparse data in high-income countries (HICs) have reported high prevalence of underdiagnosed COPD with poor clinical outcomes. Data are missing for low-income and middle-income countries (LMICs) to inform the burden and clinical outcomes of underdiagnosed COPD.
Methods
In this multinational, prospective cohort study, spirometry data were systematically collected from adults (aged 35-70 years) in urban and rural communities across 25 HICs and LMICs. Adults with spirometry airflow obstruction with physician-diagnosed airway diseases were categorised as diagnosed COPD and those without physician-diagnosed airway diseases were categorised as underdiagnosed COPD. Individuals with normal spirometry and no known airway diseases were categorised as no COPD. Data on baseline characteristics were collected via standardised interview questionnaires and follow-up data were collected every 3 years on vital status and clinical events. We examined the association between COPD status with baseline characteristics and follow-up clinical events.
Findings
Between July 11, 2002, and July 28, 2025, we collected data on 119 252 participants (baseline median age 51 years [IQR 43-59], 71 039 [59·6%] females and 48 213 (40·4%) males) with technically acceptable spirometry. The prevalence of airflow obstruction was 9·5% (11 306/119 252), of which 89·2% (10 080/11 306) constituted underdiagnosed COPD. The prevalence of airflow obstruction varied across geographical regions (6·1% [n=521/8601] in southeast Asia to 20·4% [n=785/3846] in sub-Saharan Africa) and was higher in LMICs (9·8% [n=10 120/103 758]) than in HICs (7·7% [n=1186/15 494]), with a prevalence of 90·7% (9175/10 120) for underdiagnosed COPD in LMICs. Baseline characteristics associated with underdiagnosis were younger age (≤50 years), low symptom burden, high lung function, being current or never smokers, and living in an LMIC. Compared with no COPD, underdiagnosed and diagnosed COPD were associated with higher mortality (hazard ratio 1·53 [95% CI 1·44-1·63] for underdiagnosed and 2·09 [1·83-2·40] for diagnosed COPD), respiratory events (1·97 [1·82-2·12] for underdiagnosed and 3·70 [3·25-4·21] for diagnosed COPD), and cardiovascular events (1·20 [1·13-1·27] for underdiagnosed and 1·35 [1·17-1·56] for diagnosed COPD). This association was consistent across country-income levels, age groups, smoking status, and symptom burden.
Interpretation
The high prevalence of underdiagnosed COPD and related poor outcomes suggest that a large burden of COPD is under-recognised. Since underdiagnosed COPD is mainly early and mild disease, this presents missed opportunities for early intervention that can modify disease trajectory and improve long-term health outcomes.
Funding
AstraZeneca, Population Health Research Institute, Hamilton Health Sciences Research Institute, the Canadian Institutes of Health Research, Heart and Stroke Foundation of Ontario, Canadian Institutes of Health Research's Strategy for Patient Oriented Research, Ontario SPOR Support Unit, and Ontario Ministry of Health and Long-Term Care.