People living with HIV—notably women, anyone younger than 50 and those with unchecked viral loads—are significantly more likely to experience a stroke compared with those not infected with the virus, according to a study published online ahead of print by the Journal of Acquired Immune Deficiency Syndromes.

Researchers have been reporting for years that cardiovascular disease (CVD) rates are on the rise in people with HIV, looking mostly at the number of heart attacks and clogged arteries in various cohorts. Less is known about the rate of stroke, which is another major form of CVD. It occurs when there is an interruption of the blood supply to any part of the brain. A stroke can cause disability and, in many cases, death.

To explore this matter, Felicia Chow, MD, and her colleagues studied the incidence of strokes, along with their risk factors, in two cohorts of people—one consisting of roughly 4,300 people living with HIV and another consisting of 32,000 matched individuals uninfected with the virus—between 2005 and 2007 in the Boston health care system.

The incidence of strokes was 3.75 per 1,000 person-years in the HIV-negative cohort. In the cohort of individuals living with HIV, the incidence was somewhat higher: 5.27 per 1,000 person-years.

At first glance at the incidence data, Chow and her colleagues noted that the risk of stroke appeared to be 40 percent higher in the cohort of people living with HIV. Though the risk decreased after adjusting the data to account for key differences between the two groups—HIV-positive patients were more likely to have baseline risk factors for stroke, including high blood pressure, diabetes, heart disease and being current smokers—the risk was still confirmed to be higher, by about 20 percent.

Further statistical analysis noted that HIV-positive women, but not men, were at an increased risk of stroke. The risk was doubled in women living with HIV compared with HIV-negative women—a statistically significant finding. Among men living with HIV, the risk was 18 percent higher, but this comparison with the HIV-negative men was not statistically significant.

Age was also an important consideration. HIV-positive individuals between 18 and 29 years old were more than four times more likely to experience a stroke, compared with HIV-negative individuals in the same age bracket. The risk was three times higher among HIV-positive individuals between 30 and 39 years old, compared with age-matched HIV-negative cohort subjects. Among people living with HIV between 40 and 49, the risk increase was considerably lower, but still 50 percent higher than the risk in HIV-negative people.

Only among those 50 and older was the risk similar in both groups.

As for HIV factors, higher viral loads increased the risk of stroke, whereas being on antiretroviral therapy for a longer time and having an undetectable viral load decreased the risk. Based on these observations—along with similar data available for other cardiovascular disease outcomes—the authors believe that unchecked HIV infection is associated with inflammation and unstable immune system activity that can lead to vascular problems and, ultimately, stroke.

"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," Chow's team concludes.