Dr Sonia Buist, Oregon Health & Science University, Oregon, USA and colleagues did a study of 9,425 people aged 40 years and over from 12 different countries around the world (the BOLD study). They found that the prevalence of stage II or higher COPD, as confirmed by spirometry testing, was 10.1% overall, broken down into 11.8% for men and 8.5% for women. A recent careful meta-analysis of COPD prevalence studies reported the incidence of stage II COPD to be 4.3%. The authors say: “Our estimates of the overall prevalence and staging of COPD are consistently higher than these figures, which accord with claims that COPD has generally been underestimated in the past.”
The authors add that the growing COPD burden is partly due to the aging population (with risk nearly doubling for every 10 years over the age of 40), and partly due to continuing use of tobacco, which is the most important risk factor. The variation in COPD prevalence between men and women is due mostly to differences in smoking habits. There were wide variations of COPD in the 12 worldwide sites, with Cape Town, South Africa recording the highest prevalence of combined stage II and III (men 22.2%, women 16.7%), and Hannover, Germany recording the lowest prevalence (men 8.6%, women 3.7%). The authors suggest the high rates in South Africa could be due to very high reported levels of previous tuberculosis and additional occupational exposures.
The authors conclude: “Although smoking cessation is becoming an increasingly urgent objective for an aging 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.”
In an accompanying Comment, Dr Emiel Wouters, Department of Respiratory Medicine, University Hospital Maastricht, Netherlands, says: “With quantitative data already available, it is already clear that COPD is a major disease worldwide. 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.”
In a related Review, Dr Buist and Dr David Mannino, University of Kentucky College of Public Health, Lexington, Kentucky, USA look at risk factors, prevalence and future trends of COPD. They say: "Worldwide, tobacco smoke remains the most important cause of COPD." WHO estimates that in high-income countries, 73% of COPD mortality is related to smoking, with 40% related to smoking in nations of low and middle income. They add: "Furthermore, smoking during pregnancy can negatively affect fetal lung growth and result in development of lung disease."Ageing is also a risk factor for COPD, with lung function starting to decline from its peak in young adulthood to lower levels in later life. The authors
say: "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." Such is the effect of the world's aging population on COPD prevalence, that the authors say: "Furthermore, 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 effects of occupational dust, vapours and fumes, infections, and asthma are also studied in the Review.
The authors conclude: "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."
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