The Prevalence of Chronic Obstructive Pulmonary Disease (COPD) and the Heterogeneity of Risk Factors in the Canadian Population: Results from the Canadian Obstructive Lung Disease (COLD) Study.

PURPOSE: To determine the spirometric-based prevalence of COPD across different regions in Canada and to evaluate the site heterogeneity of risk factors. PATIENTS AND METHODS: In this cross-sectional, population-based study, random samples of non-institutionalized adults aged ≥40 years were generated by random digit dialling. Participants answered an interviewer-administered questionnaire and performed spirometry before and after bronchodilator administration. COPD was defined as post-bronchodilator FEV1/FVC <0.70 (fixed ratio, FR) and as FEV1/FVC <5th percentile (lower limits of normal, LLN). Separate logistic regression models were used to compute the risk (adjusted odds ratio, aOR) for COPD. I2 and Tau2 analyses were used to evaluate heterogeneity. RESULTS: Out of 5176 (95%) participants, 4893 (47% male with mean age 56.6 years (95% confidence interval, 56.0-57.2)) had spirometry that satisfied ATS criteria. The population prevalence of COPD was 16.2% (95% CI, 14.5-17.8) by FR and 11.2% (95% CI, 9.7-12.6) by LLN. Male predominance in prevalence was shown by FR but not by LLN criteria. Patient characteristics associated with an increased risk of COPD included: age (OR 1.56; 95% CI 1.33-1.84); history of physician-diagnosed asthma (OR 3.30; 95% CI 2.42-4.49); and childhood hospitalization for respiratory illness (OR 1.81; 95% CI 1.17-2.80). In terms of smoking-related risk factors, current smoking status had the highest odds ratio (OR 3.49; 95% CI 2.55-4.80). Variance in prevalence among sites was significantly reduced by adjusting for risk factors in Tau2 analyses. Higher odds of exposure for each risk factor was found in more severe COPD, suggesting that a higher risk could be linked to the development of severe disease. CONCLUSION: This study reports the population prevalence of COPD in nine urban cities which collectively represent the majority of the Canadian population and demonstrates that heterogeneity in prevalence among sites is substantially explained by variation in associated risk factors for COPD.

A randomized clinical trial of lung volume reduction surgery versus best medical care for patients with advanced emphysema: a two-year study from Canada.

BACKGROUND: We present a summary report evaluating the efficacy of lung volume reduction surgery (LVRS) in patients with advanced emphysema in the Canadian setting. METHODS: Quality of Life measures assessed the efficacy of adding LVRS to best medical care including rehabilitation in this blinded randomized multicentered controlled trial with 2 years of follow-up. Health utility and quality-adjusted life years (QALY) were outcomes central to our economic assessment. RESULTS: None of the 32 patients randomized to the LVRS arm or 30 patients in the best medical care (BMC) arm crossed-over and no patients were lost to follow-up. Overall surgical mortality was 16% at 2 years while the overall medical mortality was 13% (p = 0.914). There were no 30-day postoperative deaths but 2 deaths (6%) occurred within 90 days of randomization. Surgery reduced the residual volume measured at 6 months by 23% (5,385 mL to 4,322 mL, p = 0.007). There was an increase in forced expiratory volume in 1 second (FEV1) of 30% (265 mL, p = 0.013) from baseline, an improvement in the six minute walk test (6MWT) of 78 meters (p = 0.045), and an increase in Health Utility Index 3 (HUI3) which peaked at 6 months with a difference of 0.16 (p = 0.129). There was a gain in QALYs of 0.21 (p = 0.19) in the LVRS-arm over the BMC-arm. The LVRS costs an additional 28,119 Canadian dollars (CAD) compared with BMC or 133,900 CAD/QALY gained. CONCLUSIONS: The addition of LVRS to best medical care including pulmonary rehabilitation improves pulmonary function, exercise activity, and quality of life in selected patients with advanced emphysema. Cost is high but in keeping with other treatment modalities currently available.