UC San Diego

Background

Rates of stroke are higher in people living with HIV compared with age-matched uninfected individuals. Causes of elevated stroke risk, including the role of viremia, are poorly defined.

Methods

Between 1 January 2006 and 31 December 2014, we identified incident strokes among people living with HIV on antiretroviral therapy at five sites across the United States. We considered three parameterizations of viral load (VL) including (1) baseline (most recent VL before study entry), (2) time-updated, and (3) cumulative VL (copy-days/mL of virus). We used Cox proportional hazards models to estimate hazard ratios (HRs) for stroke risk comparing the 75th percentile ("high VL") to the 25th percentile ("low VL") of baseline and time-updated VL. We used marginal structural Cox models, with most models adjusted for traditional stroke risk factors, to estimate HRs for stroke associated with cumulative VL.

Results

Among 15,974 people living with HIV, 139 experienced a stroke (113 ischemic; 18 hemorrhagic; eight were unknown type) over a median follow-up of 4.2 years. Median baseline VL was 38 copies/mL (interquartile interval: 24, 3,420). High baseline VL was associated with increased risk of both ischemic (HR: 1.3; 95% CI = 0.96-1.7) and hemorrhagic stroke (HR: 3.1; 95% CI = 1.6-5.9). In time-updated models, high VL was also associated with an increased risk of any stroke (HR: 1.8; 95% CI = 1.4-2.3). We observed no association between cumulative VL and stroke risk.

Conclusions

Our findings are consistent with the hypothesis that elevated HIV VL may increase stroke risk, regardless of previous VL levels.