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What Have We Learned about COPD from Epidemiology

What Have We Learned about COPD from Epidemiology. A. Sonia Buist M.D. Oregon Health & Science University, Portland, Oregon, USA. Epidemiology is the study of the distribution and determinants of disease. Definition of COPD.

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What Have We Learned about COPD from Epidemiology

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  1. What Have We Learned about COPD from Epidemiology A. Sonia Buist M.D. Oregon Health & Science University, Portland, Oregon, USA

  2. Epidemiology is the study of the distribution and determinants of disease

  3. Definition of COPD • COPD is a preventable and treatable disease with some significant extrapulmonary effects that my contribute to the severity in individual patients • Its pulmonary component is characterized by airflow limitation that is not fully reversible • The airflow limitation is usually progressive and associated with an abnormal inflammatory response of the lungs to noxious particles or gases GOLD 2006

  4. What is Epidemiology Telling Us? • COPD is more common that previously estimated, and is becoming as common in women as men as smoking habits equalize • The social and economic burden will increase worldwide as the demographics of the world’s populations changes • COPD is costly for the patient and healthcare system • We may need to change our focus from treatment to prevention

  5. How is the Burden of COPD Estimated? • Mortality • Morbidity • Prevalence • Cost • Quality of life

  6. Percent Changes in Age-Adjusted Death Rates, US, 1965-1998 Proportion of 1965 Rate 3.0 Coronary Heart Disease Stroke Other CVD COPD All Other Causes 2.5 2.0 1.5 1.0 0.5 –59% –64% –35% +163% –7% 0 1965 - 1998 1965 - 1998 1965 - 1998 1965 - 1998 1965 - 1998

  7. Explaining the Decrease in US Deaths from Coronary Disease, 1980-2000. • Ford et al. NEJM 2007; 356: 2388 • US Adults 25-84 yrs • Age-adjusted deaths for CAD fell from 543.0 to 266.7 deaths/100K (M) and from 263.3 to 134.4 (W) • 47% of decrease attributed to treatments, 44% to changing risk factors • Increases on deaths as result of increased BMI & diabetes Ford ES et al, NEJM 2007;356(23):2388-97

  8. World Health Statistics 2008, WHO

  9. COPD Mortality in the US COPD is the only one of the top 6 leading causes of death in the US that is increasing

  10. COPD Mortality by Gender, U.S., 1980-2000 Number Deaths x 1000 Year

  11. Age-Standardized Death rates from COPD in US, aged ≥18 years, by sex, 2000-2005

  12. How is the Burden of COPD Estimated? • Mortality • Morbidity • Prevalence • Cost • Quality of life

  13. Morbidity in COPD Traditionally measured by: • Physician visits • Hospitalization • Emergency visits

  14. Morbidity in COPD • May be affected by co-morbid chronic conditions that are not directly related to COPD but may have an impact on health status or may negatively interfere with COPD management • Morbidity data are greatly affected by availability of hospital beds so should be interpreted with caution

  15. Disability-Adjusted Life Years (DALYs) • A metric used by WHO • Combines premature death & disability

  16. Leading Causes Of Disability-adjusted Life-Years (DALYs) Lost Worldwide: 1990 and 2020 (projected) RANK RANK % total Disease or injury1990 2020 DALYs Lower respiratory infections 1 6 3.1 Diarrheal diseases 2 9 2.7 Ischemic heart disease 5 1 5.9 Cerebrovascular disease 6 4 4.4 Tuberculosis 7 7 3.1 Road traffic accidents 9 3 5.0 COPD 12 5 4.1 Murray & Lopez, Lancet 1997

  17. What Have We Learned from Epidemiology? • Standardized methods allow comparison across countries • Using BOLD & PLATINO standardized methods, prevalence of COPD is appreciably higher than previously reported • Different criteria & definitions for “COPD” make a big difference to reported prevalances

  18. What Else Have We Learned from Epidemiology? • There is heterogeneity across countries/sites that is not completely explained by known risk factors • Smoking and age are the most powerful risk factors • Different criteria & definitions for “COPD” make a big difference to reported prevalances • Irreversible airflow obstruction in never-smokers is still poorly understood

  19. What Have We Learned from Epidemiology? • Standardized methods allow comparison across countries • Using BOLD & PLATINO standardized methods, prevalence of COPD is appreciably higher than previously reported • Different criteria & definitions for “COPD” make a big difference to reported prevalances

  20. Two Models of International Collaboration to Measure COPD Prevalence

  21. Scientific Objectives of PLATINO & BOLD: Primary • Measure the prevalence of COPD & its risk factors by age & sex • Estimate the burden of COPD • quality of life & activity limitation • respiratory symptoms • use of health care services

  22. Scientific Objectives: Secondary • Compare different lung function criteria for the diagnosis of COPD • Determine if variations in risk factors contribute to variations in COPD prevalence • Characterize the clinical management of COPD in different countries

  23. BOLD Entry Criteria •  40 years • Men & women • Population-based e.g. random sample of population (non-institutionalized people) • Recruitment: from well-defined target population that was approved by Operations Center

  24. Methods (1) • Questionnaires: all centers used the BOLD questionnaires but added supplementary local questionnaires if they wanted • Translation: translation & back translation followed by reconciliation of any differences • Spirometry: same spirometer, same software, same methods, same data transfer, same quality control measures used

  25. Methods (2) • Data Entry & Transfer: same methods for questionnaires & spirometry. Web-based, secure, auto error detect w/ site notification, online copies of protocol, Manual of Procedures, all data forms • Participant safety: all centers obtained local ethical committee approval & observed confidentiality • Quality Control: all methods the same & standardized, edited checks for data entry

  26. What Data Are We Obtaining? • Lung function • Respiratory symptoms • Risk factors (smoking, occupation, biomass) • Respiratory medications • Health status • Health care utilization • Burden of COPD/economic & social

  27. How was COPD Defined? • Post-bronchodilatorFEV1/FVC <70% • Severity staged using GOLD criteria • For BOLD, GOLD Stage 2 & higher used to estimate burden of “clinically significant” COPD • Chronic cough, sputum, shortness of breath determined but not part of the definition of COPD

  28. Classification by Severity StageCharacteristics* I: Mild FEV1/FVC < 70%; FEV1 >80% predicted II: Moderate FEV1/FVC < 70%; 50%<FEV1< 80% predicted III: Severe FEV1/FVC < 70%; 30%> FEV1< 50% predicted IV: VerySevere FEV1/FVC < 70%; FEV1 < 30% predicted or FEV1 < 50% predicted plus chronicrespiratoryfailure GOLD 2006 *Post-Bronchodilator

  29. Airflow Obstruction by Sex* ≥ GOLD Stage 1 27% 23% 18% Prevalence, % 16% 11% Uruguay Chile Venezuela Brazil Mexico Menezes et al Lancet 2005 *Post-BD FEV1/FVC<70%

  30. The BOLD Study: Burden of Obstructive Lung Disease Initiative

  31. BOLD Sites FINISHED: Guangzhou (China);Adana (Turkey); Salzburg (Austria); Cape Town (South Africa); Reykjavik (Iceland); Krakow (Poland); Hannover (Germany); Bergen (Norway)l Vancouver (B.C., Canada); Lexington (Kentucky, USA); Manila (Philippines); Sydney (Australia); London (UK); Uppsala (Sweden); Mumbai (India) IN PROGRESS Lisbon (Portugal); Tartu (Estonia); Maastricht (The Netherlands); Pune (India); 4 additional sites in Canada & Australia; 1 additional site in Philippines PLANNING: Algeria, Tunisia, Morocco, Japan, Cambodia, Vietnam, Mongolia,

  32. Prevalence of GOLD Stage II & III+ COPD in 12 Countries by Sex & Descending Prevalence of Smoking, BOLD Study Lancet,2007; 370: 741-50 8.5% (SE 5.8) 11.8% (SE 7.9) Overall 10.1% (SE 4.8)

  33. Sydney, Australia Estimated Population Prevalence of Gold Stage II+ COPD* by pack years and sex *Post BD FEV1/FVC <70% and post BD FEV1 <80% **For the 0-10 and 10-20 pack years cell size is <20

  34. The BOLD Study: Summary Findings for COPD stage II+ • Prevalence 10.1% overall 11.8% for men 8.5% for women • Odds ratio for 10-year age increment 1.94 overall/10-yr increment Same across sites for men & women • Odds ratio for 10 pack-year increment 1.28 in women, p=0.012 site specific variation 1.16 in men, p=0.743

  35. BOLD findings on COPD prevalence • Heterogeneity in prevalence • Across sites (12 countries) • Between men & women within sites • Partly explained by site & sex differences in prevalence of smoking & other risk factors Lancet, 2007, 370: 741-50

  36. BOLD findings on COPD prevalence • Cape Town • Highest prevalence of stage II+ COPD • Had very high • reported levels of prior TB & occupational exposure • smoking rates • Cape Town, Adana, Krakow, Lexington, Manila • High prevalences of stage II+ in men • Highest reported occupational exposures in men Lancet, 2007, 370: 741-50

  37. How is the Burden of COPD Estimated? • Mortality • Morbidity • Prevalence • Cost • Quality of life

  38. Cost of COPD in US • COPD is a very costly disease • direct (diagnosis and management) • indirect (cost of disability, missed work, premature mortality and family costs) • Annual per capita expenditures for people with COPD nearly 2½x those without COPD ($8,482 vs $3,511 in 1992 study)

  39. Direct Medical Costs of COPD in US

  40. Average UK societal costs of COPD according to severity. Halpin. Proc Am Thoracic Soc 2006;3(3): 227

  41. Breakdown of Direct Costs of COPD care in the UK Halpin Proc Am Thoracic Soc 2006;3(3): 227

  42. Why is the Burden of COPD Increasing Worldwide? • Increase in exposure to risk factors (especially tobacco) in developing countries & in women

  43. COPD is a classic gene-environment interaction disease

  44. Risk Factors for COPD Smoking Nutrition Infections Socio-economic status GENES Aging Populations

  45. Trends in Risk Factors Smoking • Until 1940s, smoking prevalence in women much less than men worldwide • Smoking increased in women in many countries in 1940s and gradually equaled rates in men

  46. Mean Post-BD FEV1 in Placebo Group Sustained Quitters Continuing Smokers Annual Visit Lung Health Studies I-III

  47. Trends in Risk Factors Other Exposures • Until World War2, men were much more likely than women to have heavy occupational exposures

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