February 19, 2014
HIV-positive individuals who have reached a CD4 count of 200 or less have a 74% higher chance of suffering a myocardial infarction, the major manifestation of cardiovascular disease (CVD). This finding suggests diagnosis and treatment of HIV should begin as early as possible and be coupled with aggressive CVD risk factor management, according to a study to be published in the Journal of Acquired Immune Deficiency Syndromes.
CVD is one of the main causes of death in developed countries, but it is uncommon in people under 50 years of age. However, by 2015, the average age of HIV-positive individuals in the United States will reach 50 years, requiring an increased effort on preventing and managing CVD, especially myocardial infarction (MI). Several studies have also described a higher MI risk in people infected with HIV, but the cause of CVD in this group is complex, with many confounding factors.
In order to clarify the association between HIV infection and MI risk, Michael J. Silverberg, Ph.D., M.P.H., and colleagues conducted a cohort study using electronic medical records of adult HIV-positive and negative members of the Kaiser Permanente (KP) Northern and Southern California health plans covering the period of 1996-2009. The records included information on prescription medications (including antiretroviral drugs), inpatient and outpatient diagnoses and visits, laboratory tests, vital status, and CVD risk factors, as well as HIV-related data, such as exposure risk and duration of infection.
The statistical analyses included demographic and clinical data, such as sex and race, census-based socioeconomic status (SES), alcohol and drug abuse, overweight/obesity, and prior diagnosis of diabetes and hypertension, as well as previous use of lipid-lowering therapy. For HIV-positive subjects, the researchers also considered years known as seropositive, HIV exposure risk, duration of antiretroviral therapy (ART), recent HIV RNA levels, as well as recent and nadir CD4 counts.
HIV-positive subjects had an MI incidence rate of 283 per 100,000 person-years, while in HIV-negative patients this was 165 per 100,000 person-years. After adjustment, the rate ratio (RR) for HIV status was 1.44 (95% CI: 1.27 to 1.64), meaning that people infected with HIV had a 44% greater chance of having an MI.
When the results were stratified by recent and nadir CD4 count, and recent RNA levels, the analysis revealed that those HIV-positive subjects with nadir CD4 counts of less than 200 had an adjusted RR of 1.74 (95% CI: 1.47 to 2.06), which converts to a 74% higher chance of an MI when compared to HIV-negative individuals.
The authors suggest that nadir CD4 count may contribute to MI, because atherosclerosis is considered a consequence of a chronic inflammatory process in which immune cells and their mediators contribute to its development. "Chronic inflammation is typically higher among those with low CD4 [counts]," Silverberg stated.
The researchers caution that since the majority of their HIV-positive subjects were male (90.6%), which reflects the state of the epidemic in California, their findings may not be as valid for women. However, they point out that their results may become increasingly generalizable in the United States due to health care reform. "Our study population inherently accounts for access to care, since all subjects are insured. With the Affordable Care Act, more patients will be insured, resulting in higher applicability of our findings," explained Silverberg.
Finally, the researchers argue that since nadir CD4 count is not modifiable, CD4-related MI risk may not be easily reversible. Thus, they conclude, there should be a greater effort to diagnose and treat HIV as early as possible, which, if combined with aggressive traditional CVD risk factor management, may result in a similar MI burden in the HIV-positive population as the general population.
Fred Furtado is a science writer based in Rio de Janeiro, Brazil.
Follow Fred on Twitter: @Patchlord.