COPD Disease Burden Heavy and Increasing

Laurie Barclay, MD

September 4, 2007 — The burden of chronic obstructive pulmonary disease (COPD) is heavy and increasing, according to the results of a population-based prevalence study reported in the September 1 issue of The Lancet. The annual mortality from COPD is about the same as from HIV/AIDS, mandating better primary and secondary prevention policies.
"Chronic obstructive pulmonary disease...is a growing cause of morbidity and mortality worldwide, and accurate estimates of the prevalence of this disease are needed to anticipate the future burden of COPD, target key risk factors, and plan for providing COPD-related health services," write A. Sonia Buist, MD, from the Oregon Health and Sciences University in Portland, Oregon, and colleagues from the Burden Of Obstructive Lung Disease (BOLD) Collaborative Research Group. "We aimed to measure the prevalence of COPD and its risk factors and investigate variation across countries by age, sex, and smoking status."
According to the World Health Organization Global Burden of Disease Project, COPD was the fifth leading cause of death worldwide in 2001 and will be the third leading cause by 2020, partly because of the aging of the world's population and partly because of the continued use of tobacco.
At 12 sites worldwide, 9425 participants aged 40 years and older underwent postbronchodilator spirometry testing and completed questionnaires concerning respiratory symptoms, health status, and exposure to risk factors for COPD. Prevalence estimates for COPD were based on the Global Initiative for Chronic Obstructive Lung Disease staging criteria and adjusted for the target population. The investigators used logistic regression to calculate adjusted odds ratios (ORs) for COPD associated with 10-year age increments, as well as for 10-pack-year increments, calculated as the number of cigarettes smoked per day divided by 20 and multiplied by the number of years that the participant smoked. Pooled estimates for these risk factors were determined by meta-analyses.
For stage 2 or higher COPD, prevalence was 10.1% ± 4.8% overall, 11.8% ± 7.9% for men, and 8.5% ± 5.8% for women. For 10-year age increments, ORs were similar in both sexes and across sites, with an overall pooled estimate of 1.94 (95% confidence interval [CI], 1.80 – 2.10) per 10-year increment. Site-specific pack-year ORs varied significantly in women (pooled OR = 1.28; 95% CI, 1.15 – 1.42; P = .012). However, site-specific pack-year ORs did not vary significantly in men (pooled OR = 1.16; 95% CI,1.12 – 1.21; P = .743).
Across the 12 worldwide sites, prevalence of combined stage 2 and 3 COPD varied widely, being highest in Cape Town, South Africa (22.2% in men and 16.7% in women), and lowest in Hannover, Germany (8.6% in men and 3.7% in women). The high rates in South Africa were attributed to very high reported levels of previous tuberculosis as well as occupational exposures.
Study limitations include small absolute number of patients with COPD within any particular site, preventing specific types of within-site analyses; low response rates at some sites, introducing potential response bias; and lack of generalizability from any individual site's data to a broader population.
"This worldwide study showed higher levels and more advanced staging of spirometrically confirmed COPD than have typically been reported," the authors write. "However, although age and smoking are strong contributors to COPD, they do not fully explain variations in disease prevalence — other factors also seem to be important. Although smoking cessation is becoming an increasingly urgent objective for an ageing worldwide population, a better understanding of other factors that contribute to COPD is crucial to assist local public-health officials in developing the best possible primary and secondary prevention policies for their regions."
The BOLD study was funded in part by Altana, Aventis, AstraZeneca, Boehringer-Ingelheim, Chiesi, GlaxoSmithKline, Merck, Novartis, Pfizer, Schering-Plough, Sepracor, and the University of Kentucky.
Some of the authors report various financial relationships with GlaxoSmithKline, Pfizer, Boehringer Ingelheim, AstraZeneca, ALTANA, Novartis, Merck, Chiesi, Schering Plough, Sepracor, Ortho Biotech, Eli Lilly, Dey, Air Liquide Healthcare P/L, Polpharma, Ivax Pharma Poland, Pliva Kraków, Adamed, Linde Gaz Polska, Lek Polska, Tarchomińskie Zakłady Farmaceutyczne Polfa, Starostwo Proszowice, Skanska, Zasada, Agencja Mienia Wojskowego w Krakowie, Telekomunikacja Polska, Biernacki, Biogran, Amplus Bucki, Skrzydlewski, Sotwin, and/or Agroplon.
In an accompanying Comment, Emiel M. Wouters, MD, FCCP, from the University Hospital Maastricht, in the Netherlands, describes the significant worldwide societal burden imposed by COPD.
"With quantitative data already available, it is already clear that COPD is a major disease worldwide," Dr. Wouters says. "Recognition of this fact obligates us to make efforts towards increasing public awareness and efforts toward the adoption of an integrated approach aimed at reducing or stabilising the present and future burden of disease generated by COPD.... More research focused on non-smokers and sex differences is necessary if we are to improve our understanding of the pathogenesis and heterogeneity of COPD."
Dr. Wouters reports no relevant financial relationships.
An accompanying review by Dr. Buist and David Mannino, MD, from the University of Kentucky College of Public Health in Lexington, describes COPD risk factors, such as occupational dust and fumes, infections, and asthma, as well as COPD prevalence and future trends. They acknowledge that tobacco smoke is still the most important cause of COPD worldwide.
"In looking to the future, one cannot ignore the changing demographics of the world's population and the reality that COPD is a disease of ageing," Dr. Buist and Dr. Mannino write. "If every smoker in the world were to stop smoking today, the rates of COPD would probably continue to increase for the next 20 years.... The challenge we will all face in the next few years will be implementation of cost-effective prevention and management strategies to stem the tide of this disease and its cost."
Lancet. 2007;370:741–750.