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

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.

To measure the survival differences between men and women with oxygen-dependent COPD.

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.

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.

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).

Among patients with COPD on LTOT, women were more likely to die than men.