Chronic obstructive pulmonary disease (COPD): exacerbations and costs.

Background: Chronic obstructive pulmonary disease (COPD) is a major contributor to morbidity and mortality worldwide. Being a preventable disease in most cases, the burden on both patients and society may be reduced substantially. Previous research on COPD burden has focused on symptoms and treatment costs, while studies on working capacity and total societal costs are scarce. Additionally, burden has mainly been studied in selective samples from outpatient wards or hospitals, and is not representative for a general population. The objectives of this PhD thesis were to estimate the worldwide burden of unemployment due to COPD, to estimate the incidence and predictors of COPD exacerbations, to calculate the costs associated with COPD and its exacerbations, and estimate of the productivity loss in Norway. A secondary aim, was to compare our estimates in a selected hospital sample to those in a general population sample. Methods: For the paper on worldwide unemployment, we used cross-sectional data from 18710 participants in 26 sites in the Burden of Obstructive Lung Disease (BOLD) study. Odds ratios (ORs) for unemployment associated with chronic airflow obstruction (CAO) was estimated with a multilevel mixed-effects generalized linear model. For the three other papers, we used the EconCOPD dataset which is a one-year prospective, observational study including 132 controls and 81 COPD cases from a general population, and 205 COPD patients from a hospital-register. Multivariable regression models were fitted to find potential adjusted associations between predictors and outcome. Results: The adjusted odds ratio (95% confidence interval) for unemployment in the BOLD study was 1.43 (1.14 – 1.79) for CAO subjects. Age, per 10-year increment, and lower education were important risk factors for unemployment in high-income sites ((4.02 (3.53–4.57) and 3.86 (2.80–5.30), respectively), while female sex was important in low- to middle-income sites (3.23 (2.66–3.91)). In the EconCOPD study, the annual incremental productivity losses were 5.8 (1.4 to 10.1) and 330.6 (95% CI 327.8 to 333.3) days, comparing population-recruited and hospital-recruited patients with COPD to controls, respectively. Further, COPD patients from the population- and hospital-based samples experienced on average 0.4 utilization-defined and 2.9 symptom-defined versus 1.0 and 5.9 annual exacerbations, respectively. The incidence rate ratios for utilization-defined AECOPD were 2.45 (95% CI 1.22–4.95), 3.43 (95% CI 1.59–7.38), and 5.67 (95% CI 2.58–12.48) with Global Initiative on Obstructive Lung Disease spirometric stages II, III, and IV, respectively. The average annual disease-related costs for a COPD patient from the hospital sample was nearly twice as high as for a COPD case from the population sample (€26,518 vs €15,021), and nearly four times as high as for a control subject (€6740). The productivity losses were substantially higher than the treatment related costs. Conclusion: Globally, CAO was associated with significantly increased levels of unemployment. In Norway, COPD was associated with a significantly higher productivity loss, and higher costs, compared to control subjects. Further on, the COPD patients from the hospital sample had a significantly higher burden of exacerbations, and higher costs than the COPD cases from the general population. Sampling from a general population gives more externally valid results when studying the burden of COPD.Doktorgradsavhandlin