Low CD4⁺ T Cell Count Is a Risk Factor for Cardiovascular Disease Events in the HIV Outpatient Study

Background. Traditional cardiovascular disease (CVD) risk factors, human immunodeficiency virus (HIV) infection, and antiretroviral (ARV) agents have been associated with CVD events in HIV-infected patients. We investigated the association of low CD4⁺ T lymphocyte cell count with incident CVD in a cohort of outpatients treated in 10 HIV specialty clinics in the United States. Methods. We studied patients who were under observation from 1 January 2002 (baseline), categorized them according to National Cholesterol Education Program guidelines into 10-year cardiovascular risk score (10-y CVR) groups , and observed them until CVD event, death, last HIV Outpatient Study contact, or 30 September 2009. We calculated rates of incident CVD events and identified associated baseline risk factors using Cox proportional hazard models. We also performed a nested case-control study to examine the association of latest CD4⁺ cell count with CVD events. Results. Among 2005 patients, 148 experienced incident CVD events. CVD incidence increased steadily from 0.4 to 3.0 events per 100 person-years from lowest to highest 10-y CVR group (P < .001). In multivariable Cox analyses adjusted for 10-y CVR, CD4⁺ cell count <350 cells/mm³ was associated with incident CVD events (hazard ratio, 1.58 [95% confidence interval, 1.09-2.30], compared with >500 cells/mm³), suggesting an attributable risk of ̃20%. In the multivariable case-control analyses, traditional CVD risk factors and latest CD4⁺ cell count <500 cells/mm³, but not cumulative use of ARV class or individual drugs, were associated with higher odds of experiencing CVD events. Conclusion. CD4⁺ count <500 cells/mm ³ is an independent risk factor for incident CVD, comparable in attributable risk to several traditional CVD risk factors in the HIV Outpatient Study cohort.