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HIV Infection Linked to Increased Stroke Risk

HIV positive people may have a higher risk of stroke independent of traditional risk factors, with the largest relative increase among younger people and women, according to study findings published in the May 10, 2012, advance online edition of the Journal of Acquired Immune Deficiency Syndromes.

Several observational studies have found that people with HIV are at greater risk for cardiovascular disease and events such as heart attacks and strokes, but it is unclear whether this is related to chronic HIV infection itself, resulting inflammatory and metabolic changes, side effects of antiretroviral drugs, traditional risk factors, or some combination. Further, studies have produced inconsistent results, so the magnitude of risk increase -- if in fact there is one -- is unclear.

Felicia Chow and colleagues from Brigham and Women's Hospital and Massachusetts General Hospital in Boston compared rates of ischemic stroke and looked at stroke risk factors in people with and without HIV. Ischemic strokes are caused by blocked blood flow to the brain -- often due to a blood clot in a small vessel -- in contrast with hemorrhagic strokes due to uncontrolled bleeding.

The researchers identified a cohort of 4308 HIV positive patients and 32,000 matched HIV negative control subjects seen between 1996 and 2009. While demographic risk factors were matched, the HIV positive group was significantly more likely to have other traditional risk factors including smoking, high blood pressure, diabetes, and various types of heart problems.

Results

·      A total of 132 strokes occurred in the HIV positive group and 782 in the HIV negative group during the study period.

·      The incidence rate of ischemic stroke was 5.27 per 1000 person-years among HIV positive people compared with 3.75 per 1000 person-years in the HIV negative control group.

·      The unadjusted hazard ratio (HR) was 1.40, or a significant 40% increase in risk for people with HIV (P < 0.001).

·      HIV infection remained an independent predictor of stroke after controlling for demographic factors and other stroke risk factors, with an adjusted hazard ratio of 1.21 (P = 0.043).

·      The relative increase in stroke rates for HIV positive versus HIV negative individuals was significantly higher for younger people, as shown by decreasing incidence rate ratios (IRR) at older ages:

o      Age 18-29: IRR 4.42, or more than 4-fold higher risk;

o      Age 30-39: IRR 2.96, or about 3 times higher risk;

o      Age 40-49: IRR 1.53;

o      Age 50 and above: no significant risk increase.

·      The relative risk increase was larger and statistically significant for women (HR 2.16), but non-significant when looking at men alone (HR 1.18).

·      Among people with HIV, higher viral load was also a significant predictor of increased stroke risk (HR 1.10; P = 0.001), while antiretroviral therapy significantly decreased risk (P < 0.001).

Based on these findings, the study authors concluded, "Stroke rates were increased among HIV-infected patients, independent of common stroke risk factors, particularly among young patients and women."

"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," they elaborated in their discussion.

Because smoking and high blood pressure were factors that were more common among people with HIV, the researchers recommended that "[t]hese risk factors might therefore be particularly targeted for intervention in the HIV population."

5/30/12

Reference

FC Chow, S Regan, S Feske, et al. Comparison of Ischemic Stroke Incidence in HIV-Infected and Non-HIV-Infected Patients in a U.S. Health Care System. Journal of Acquired Immune Deficiency Syndromes. May 10, 2012 (Epub ahead of print).