Sex differences in survival of oxygen-dependent patients with chronic obstructive pulmonary disease

Rationale: 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. Objectives: 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. Measurements: 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. Main 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_O2, 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_O2 (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.