Patients taking long-term antiretroviral therapy may be less likely than their HIV-negative peers to develop heart disease, according to a US study published in the August 20th edition of AIDS.
Researchers from the large US Multicenter AIDS Cohort (MACS), which involves HIV-positive and HIV-negative men looked for the presence and extent of calcification of the coronary artery. Calcium deposits in the coronary artery have been shown to be an important risk factor for heart disease.
Their research showed that HIV-positive men were slightly more likely than their HIV-negative peers to have calcium present in their coronary artery. But when they looked at the extent of this calcification, they found that it was much lower in patients taking long-term HIV treatment than in HIV-negative men of the same age and race.
A study published in the same edition of AIDS involving both MACS and the Women’s Interagency HIV Study (WIHS) showed that HIV treatment did not increase the risk of vascular disease, however a low CD4 cell count did.
A number of studies have looked at risk of heart disease and hardening of the arteries in patients taking antiretroviral therapy and have yielded conflicting results, possibly because the studies had different designs. The results of these studies were also limited because they were observational.
Investigators from the ongoing MACS study therefore designed a study to look at the prevalence and extent of calcification in the coronary artery. The MACS study has a prospective design allowing researchers to assess the risk of coronary calcification over time. Another strength of the MACS study is that it involves both HIV-positive and HIV-negative men.
The study involved 947 individuals. All were aged over 40, had no history of heart disease, and weighed less than 138 kg. A total of 332 individuals were HIV-negative, 84 were HIV-positive but not taking anti-HIV drugs, and 531 were HIV-positive and had experience of antiretroviral therapy. The presence and extent of coronary calcification was assessed using CT scans.
There were important baseline differences in cardiovascular risk factors between these three groups of patients, but the design of the study meant that the investigators were able to adjust for these in the statistical analyses of their results.
Overall, the prevalence of calcification was 32%. Prevalence was higher amongst older patients, being 44% amongst those aged 55. In all, 40% of HIV-negative individuals had calcification of the coronary artery compared to an overall prevalence of 48% amongst HIV-positive patients. HIV-positive individuals who had been taking anti-HIV drugs for eight years or more were the group most likely to have evidence of calcification in their coronary artery (51%).
However, when the researchers adjusted their findings to take account of baseline risk factors for heart disease they found that HIV-positive patients overall only had a modest increase in the risk of coronary calcification (odds ratio [OR] 1.26, 95% confidence interval [CI], 0.93 – 1.77). HIV-positive patients who had taken HIV treatment for eight or more years still remained the group most likely to have some calcification in the coronary artery (OR, 1.53, 95% CI, 1.04 – 2.25), but this risk was not statistically significant and adjustment for individual risk factors such as race, family history of heart disease, cholesterol levels, and body mass index reduced this risk even further.
Next the researchers looked at the extent of coronary calcification. They found that long-term use of antiretroviral medication was consistently associated with less extensive calcification of the coronary artery. Indeed, calcification scores were 44% lower amongst patients who had been taking HIV treatment for eight or more years than amongst HIV-negative patients. When the researchers took into account age and race, they found that the adjusted risk of calcification of the coronary artery was reduced by 40% in patients who had taken between one and seven years of HIV treatment compared to matched HIV-negative individuals (OR, 0.60, 95% CI. 0.36 – 0.99), and by 53% for individuals treated with anti-HIV drugs for eight or more years (OR, 0.47, 95% CI, 0.27 – 0.80).
Further study of calcification of the coronary artery is planned by the investigators involving three additional years of follow-up. The aim will be to see if progression of coronary calcification is slowed amongst patients taking antiretroviral therapy and those taking lipid-lowering drugs. The investigators also wish to determine the risk factors for new cases of calcification of the coronary artery.
Kingsley LA et al. Subclinical coronary atherosclerosis, HIV infection and antiretroviral therapy: Multicenter AIDS Cohort Study. AIDS 22: 1589 – 1599, 2008.