title: Sex differences in survival of oxygen-dependent patients with chronic obstructive pulmonary disease.
abstract: BACKGROUND
  Chronic obstructive pulmonary disease (COPD) is a leading cause of death worldwide. The prevalence of COPD is rising among women and is approaching that of men, but it is not known if sex affects survival.
  
  
  OBJECTIVE
  To measure the survival differences between men and women with oxygen-dependent COPD.
  
  
  METHODS
  We conducted a 7-yr prospective cohort study of 435 outpatients with COPD (184 women, 251 men) referred for long-term oxygen therapy (LTOT) at two respiratory clinics in Sao Paulo, Brazil. Baseline data were collected on enrollment into oxygen therapy, when patients were clinically stable.
  
  
  METHODS
  We examined the effect of sex on survival using Kaplan-Meier survival curves, and then used Cox proportional hazards models to control for potential confounders.
  
  
  RESULTS
  In unadjusted analyses, we observed a nonsignificant trend toward increased mortality for women (hazard ratio, 1.28; 95% confidence interval, 0.98-1.68; p = 0.07). After accounting for potential confounders (age, pack-years smoked, Pa(O(2)), FEV(1), body mass index), females were at a significantly higher risk of death (hazard ratio, 1.54; 95% confidence interval, 1.15-2.07; p = 0.004). Other independent predictors of death were lower Pa(O(2)) (p < 0.001) and lower body mass index (p < 0.05).
  
  
  CONCLUSIONS
  Among patients with COPD on LTOT, women were more likely to die than men.
authors.affiliation: State Public Hospital of São Paulo, São Paulo, Brazil. mchrismachado@pneumo.epm.br
authors.forename: Maria-Christina L
authors.initials: MC
authors.lastname: Machado
authors.forename: Jerry A
authors.initials: JA
authors.lastname: Krishnan
authors.forename: Sonia A
authors.initials: SA
authors.lastname: Buist
authors.forename: Andrew L
authors.initials: AL
authors.lastname: Bilderback
authors.forename: Guilherme P
authors.initials: GP
authors.lastname: Fazolo
authors.forename: Michelle G
authors.initials: MG
authors.lastname: Santarosa
authors.forename: Fernando
authors.initials: F
authors.lastname: Queiroga
authors.forename: William M
authors.initials: WM
authors.lastname: Vollmer
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005500:Follow-Up Studies; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D010102:Oxygen Inhalation Therapy; D016016:Proportional Hazards Models; D029424:Pulmonary Disease, Chronic Obstructive / Q000401:mortality* / Q000503:physiopathology / Q000628:therapy*; D012737:Sex Factors; D016019:Survival Analysis; D015996:Survival Rate