title: Chronic obstructive pulmonary disease mortality and prevalence: the associations with smoking and poverty--a BOLD analysis.
abstract: BACKGROUND
  Chronic obstructive pulmonary disease (COPD) is a commonly reported cause of death and associated with smoking. However, COPD mortality is high in poor countries with low smoking rates. Spirometric restriction predicts mortality better than airflow obstruction, suggesting that the prevalence of restriction could explain mortality rates attributed to COPD. We have studied associations between mortality from COPD and low lung function, and between both lung function and death rates and cigarette consumption and gross national income per capita (GNI).
  
  
  METHODS
  National COPD mortality rates were regressed against the prevalence of airflow obstruction and spirometric restriction in 22 Burden of Obstructive Lung Disease (BOLD) study sites and against GNI, and national smoking prevalence. The prevalence of airflow obstruction and spirometric restriction in the BOLD sites were regressed against GNI and mean pack years smoked.
  
  
  RESULTS
  National COPD mortality rates were more strongly associated with spirometric restriction in the BOLD sites (<60 years: men rs=0.73, p=0.0001; women rs=0.90, p<0.0001; 60+ years: men rs=0.63, p=0.0022; women rs=0.37, p=0.1) than obstruction (<60 years: men rs=0.28, p=0.20; women rs=0.17, p<0.46; 60+ years: men rs=0.28, p=0.23; women rs=0.22, p=0.33). Obstruction increased with mean pack years smoked, but COPD mortality fell with increased cigarette consumption and rose rapidly as GNI fell below US$15 000. Prevalence of restriction was not associated with smoking but also increased rapidly as GNI fell below US$15 000.
  
  
  CONCLUSIONS
  Smoking remains the single most important cause of obstruction but a high prevalence of restriction associated with poverty could explain the high 'COPD' mortality in poor countries.
authors.affiliation: National Heart & Lung Institute, Imperial College, , London, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Burney
authors.forename: Anamika
authors.initials: A
authors.lastname: Jithoo
authors.forename: Bernet
authors.initials: B
authors.lastname: Kato
authors.forename: Christer
authors.initials: C
authors.lastname: Janson
authors.forename: David
authors.initials: D
authors.lastname: Mannino
authors.forename: Ewa
authors.initials: E
authors.lastname: Nizankowska-Mogilnicka
authors.forename: Michael
authors.initials: M
authors.lastname: Studnicka
authors.forename: Wan
authors.initials: W
authors.lastname: Tan
authors.forename: Eric
authors.initials: E
authors.lastname: Bateman
authors.forename: Ali
authors.initials: A
authors.lastname: Koçabas
authors.forename: William M
authors.initials: WM
authors.lastname: Vollmer
authors.forename: Thorarrin
authors.initials: T
authors.lastname: Gislason
authors.forename: Guy
authors.initials: G
authors.lastname: Marks
authors.forename: Parvaiz A
authors.initials: PA
authors.lastname: Koul
authors.forename: Imed
authors.initials: I
authors.lastname: Harrabi
authors.forename: Louisa
authors.initials: L
authors.lastname: Gnatiuc
authors.forename: Sonia
authors.initials: S
authors.lastname: Buist
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D005541:Forced Expiratory Volume; D014943:Global Health; D006801:Humans; D008297:Male; D008875:Middle Aged; D011203:Poverty / Q000706:statistics & numerical data*; D015995:Prevalence; D029424:Pulmonary Disease, Chronic Obstructive / Q000401:mortality* / Q000503:physiopathology; D018570:Risk Assessment / Q000379:methods*; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology*; D015996:Survival Rate / Q000639:trends; D006113:United Kingdom / Q000453:epidemiology; D014797:Vital Capacity; D055815:Young Adult
keywords: COPD epidemiology; Lung Physiology; Tobacco and the lung