HIV infection is an independent risk factor for stroke

Michael Carter
Published: 18 May 2012

HIV infection is associated with an increased risk of stroke, US research published in the online edition of the Journal of Acquired Immune Deficiency Syndromes shows. The association between HIV and stroke was significant even after controlling for traditional risk factors. Viral load was the most important HIV-specific risk factor.

“Stroke risk was increased in association with increasing viral load, suggesting that poorer virologic control and its inflammatory and immunologic sequelae may increase cerebrovascular risk,” comment the authors.

It is now well recognised that HIV is associated with an increased risk of cardiovascular disease. Despite this, the effect of HIV on the risk of stroke is unclear.

Investigators in Boston therefore designed a study to determine if HIV infection was associated with an increased risk of stroke. They also wished to see if any HIV-specific factors were associated with the disease.

They compared incidence of stroke between 4308 HIV-positive people seen between 2005 and 2007 to that observed in 32,000 matched HIV-negative people as controls.

There was a higher prevalence of traditional stroke risk factors among the patients with HIV. These included hypertension, diabetes, smoking, cardiomyopathy, left-sided valvular heart disease and heart failure (all p < 0.001).

A total of 132 strokes were observed in the HIV-positive patients, with 782 events recorded in the HIV-negative controls.

Incidence of stroke was 5.27 per 1000 patient-years for the people with HIV and 3.75 per 1000 patient-years for the HIV-negative participants.

In the investigators’ unadjusted analysis, HIV infection was associated with a 40% increase in the risk of stroke (HR = 1.40; 95% CI, 1.17-1.69, p < 0.001).

Taking into account traditional risk factors attenuated this finding. Nevertheless, risk of stroke was still significantly higher for the HIV-positive participants (HR = 1.21; 95% CI, 1.01-1.46, p = 0.046).

“Smoking and hypertension were risk factors that were more highly prevalent among the HIV population and significantly associated with stroke,” note the authors. “These risk factors might therefore be particularly targeted for intervention in the HIV population.”

The association between HIV infection and an increased risk of stroke was significant for women (HR = 2.16; 95% CI, 1.53-3.04, p < 0.001), but not for men (HR = 1.18; 95% CI, 0.95-1.47, p = 0.14).

The increased risk of stroke for people with HIV was restricted to younger people (18 to 49 years). For instance, HIV-positive people aged between 18 and 29 had a four-fold increase in their risk of stroke compared to HIV-negative people of the same age (IRR = 4.42; 95% CI, 1.56-11.09).

“The effect of HIV on stroke may be more pronounced in younger patients before traditional age-related vascular risk factors begin to play a major role,” suggest the authors.

Analysis of HIV-specific factors showed that higher viral load increased the risk of stroke (p = 0.001).

Longer duration of the use of antiretroviral therapy reduced the risk of stroke (p < 0.001), as did a viral load below 400 copies/ml (p = 0.008).

“We demonstrate the novel finding that stroke risk is increased for HIV patients relative to control patients and that this risk persists in part after accounting for traditional stroke risk factors,” conclude the investigators. “The demonstrated association between HIV and stroke should prompt medical providers to view HIV as a risk factor for stroke and to have a low threshold to aggressively modify vascular risk, particularly in women and the young – groups not typically identified as high-risk.”

Reference

Chow FC et al. Comparison of ischemic stroke incidence in HIV-infected and non-infected patients in the U.S. health care system. J Acquir Immune Defic Synr, onine edition. DOI: 10.1097/QAI.0b013e31825c7f24, 2012.