Study finds high CD4 cell counts associated with reduced risk of ischemic stroke for those with HIV

June 24, 2014

OAKLAND, Calif., June 24, 2014 -- A 15-year study found that HIV-positive individuals had a 40 percent increased risk of ischemic stroke, however stroke rates were nearly the same for HIV-positive individuals with high CD4 cell counts as for HIV-negative subjects.

The study, published recently in AIDS, the official journal of the International AIDS Society, covered the years 1996 through 2011 and included nearly 25,000 HIV-positive individuals.

Ischemic stroke is caused by plaque build-up in blood vessels, which can lead to constriction or actual obstruction of blood and oxygen flow to the brain. A CD4 cell count below 500 is considered a sign of a weakened immune system as it indicates lower numbers of white blood cells that fight infections and inflammation.

"Recent CD4 cell count was the strongest HIV-specific risk factor, suggesting an effect of current immunodeficiency on ischemic stroke risk," said senior author Michael J. Silverberg, PhD, MPH, an investigator with the Kaiser Permanente Division of Research in Oakland, California. "Notably, HIV-positive individuals with recent CD4 cell counts of 500 or more had no excess risk of ischemic stroke compared with HIV-negative individuals."

If the association between immunodeficiency on ischemic stroke risk is causal, the researchers concluded, early and consistent treatment with antiretroviral therapy to maintain immune function, combined with mitigation of stroke risk factors, may result in a similar risk of ischemic stroke among HIV-positive individuals compared with the general population.

"Our results suggest that maintenance of immune function may protect against ischemic stroke," said lead author Julia L. Marcus, PhD, MPH of the Division of Research. "Given recent calls to reduce or abandon CD4 monitoring among HIV-positive individuals with viral suppression, our data suggest that the CD4 cell count may be useful beyond its role in HIV disease monitoring."

The researchers found that, while ischemic stroke rates were higher over the entire study period, rates among HIV-positive individuals converged with rates for demographically-similar HIV-negative individuals by 2010-2011. A similar improved trend in risk of heart attack was observed previously in this same study cohort.

"As awareness of cardiovascular complications associated with antiretroviral therapy has increased, improved risk-factor management among HIV-positive individuals may have contributed to a decreasing risk over time," said co-author Daniel B. Klein, MD, chief of infectious diseases for Kaiser Permanente San Leandro. "It may also be that stroke risk has been mitigated by the earlier and wider use of antiretroviral therapy regimens with less cardiovascular risk."
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Other authors on the study include Wendy A. Leyden, MPH, Leo B. Hurley, MPH, Charles P. Quesenberry, Jr, PhD, Division of Research, Kaiser Permanente Northern California; Chun R. Chao, PhD, Department of Research and Evaluation, Kaiser Permanente, Pasadena, California; Michael A. Horberg, MD, MAS, Mid-Atlantic Permanente Research Institute, Rockville, Maryland; Felicia C. Chow, MD, University of California, San Francisco; and William J. Towner, MD, Kaiser Permanente Southern California.

About the Kaiser Permanente Division of Research

The Kaiser Permanente Division of Research conducts, publishes and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and the society at large. It seeks to understand the determinants of illness and well-being and to improve the quality and cost-effectiveness of health care. Currently, the Division's 550-plus staff are working on more than 350 ongoing research studies in behavioral health and aging, cancer, cardiovascular and metabolic conditions, health care delivery and policy, infectious diseases, vaccine safety and effectiveness, and women's and children's health. For more information, visit http://www.dor.kaiser.org.

About Kaiser Permanente

Kaiser Permanente is committed to helping shape the future of health care. We are recognized as one of America's leading health care providers and not-for-profit health plans. Founded in 1945, our mission is to provide high-quality, affordable health care services and to improve the health of our members and the communities we serve. We currently serve approximately 9.3 million members in eight states and the District of Columbia. Care for members and patients is focused on their total health and guided by their personal physicians, specialists and team of caregivers. Our expert and caring medical teams are empowered and supported by industry-leading technology advances and tools for health promotion, disease prevention, state-of-the-art care delivery and world-class chronic disease management. Kaiser Permanente is dedicated to care innovations, clinical research, health education and the support of community health. For more information, go to kp.org/share.

Kaiser Permanente

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