Hemoglobin may contribute to sex differences in mortality among HIV-infected persons in care.

Background: Some retrospective studies have found that HIV-infected women have a higher mortality risk than men after adjusting for baseline characteristics, while others have not. Anemia is a known predictor of HIV-related mortality. We assessed whether anemia contributed to the sex difference in mortality in our cohort.

Methods: We conducted a retrospective cohort study among HIV-infected persons in care at the Comprehensive Care Center (Nashville, TN) between 1998 and 2009. Cox proportional hazards models compared time from first clinic visit to death and AIDS-defining events (ADE), adjusted for baseline characteristics with and without baseline hemoglobin.

Results: Of 3,633 persons, 879 (24%) were women. Women had lower median baseline hemoglobin compared to men: 12.4 g/dL (inter-quartile range (IQR) 11.3-13.4) vs. 14.4 (IQR 13.1-15.5), respectively (P<0.001). In multivariable models without hemoglobin, the risk of death was higher among women: hazard ratio (HR) 1.46 (95% confidence interval (CI) 1.17, 1.82; P=0.001). In multivariable models with hemoglobin, the risk of death in women was diminished and no longer statistically significant: HR 1.2 (95% CI 0.93, 1.55; P=0.17). The risk of ADE was higher among women in both models, but not statistically significant: HR 1.1 (95% CI 0.85-1.42; P=0.46) in the model without hemoglobin and 1.11 (95% CI 0.82-1.48; P=0.50) in the model with hemoglobin. Hemoglobin was a strong predictor of death: HR 0.88 per 1 g/dL increase (95% CI 0.83, 0.93; P<0.001).

Conclusion: In our study population of HIV-infected persons in care, women had lower baseline hemoglobin, and lower hemoglobin contributed to their higher risk of ADE and death.