February 25, 2016
Coronary artery calcium, a signal of future heart disease, developed more often in middle-aged HIV-positive men than in a group of HIV-negative men the same age.1 Cigarette smoking and insulin resistance, which can lead to diabetes, also predicted more frequent development of coronary artery calcium in men with HIV.
Combined analysis of 20 studies found that HIV-positive people who never took antiretroviral therapy ran a 61% higher risk of cardiovascular disease than HIV-negative people.2 In the same study antiretroviral-treated people with HIV had a twice higher risk of cardiovascular disease than the general population.
Researchers are still working out why HIV-positive people have this higher risk of heart disease than HIV-negative people. One way to find out is to compare rates of heart disease signals in HIV-positive people before they have heart disease with rates of the same signal in a similar group of people without HIV. At the same time researchers can see how the HIV-positive and negative groups differ in heart disease risk factors. It may be possible to prevent or control many of these risk factors and thus to lower the risk of heart disease.
Coronary artery calcium is one cardiovascular disease signal that can be measured over time to see (1) how often it develops in people who do not already have coronary artery calcium and (2) how often coronary artery calcium gets worse. In the general population coronary artery calcium is a strong predictor of future heart disease, such as myocardial infarction (heart attack). Coronary artery calcium can be measured over time with computed tomography (CT), a scanning technique that does not require opening up the body to look directly at the heart.
Researchers working with the Multicenter AIDS Cohort Study conducted this study to compare the new development (incidence) and progression (worsening) of coronary artery calcium in men with and without HIV infection.
The Multicenter AIDS Cohort Study (MACS) studies gay or bisexual men with or without HIV infection in four U.S. cities. Men make study visits twice a year to undergo various tests and update personal and health-related information. The coronary artery calcium study involved men over 40 years old who had two or more coronary artery CT scans and did not already have cardiovascular disease.
Researchers determined whether men had coronary artery calcium on their first CT scan. Among those who did not already have coronary artery calcium, the researchers looked at later scans to see if it developed during the study period. When a CT showed coronary artery calcium, the investigators checked later scans to see if the coronary artery calcium score got higher, indicating more calcium and a greater risk of heart disease. Throughout the study the researchers checked MACS records for factors that could affect development of cardiovascular disease, like age, smoking, body mass index, high blood pressure, insulin resistance, and diabetes.
The MACS investigators used standard statistical methods (1) to compare rates of newly detected coronary artery calcium in men with versus without HIV, (2) to compare rates of worsening coronary artery calcium in men with versus without HIV, and (3) to identify independent risk factors for coronary artery calcium detection. Independent risk factors are those that affect risk no matter what other risk factors a person has.
The study group included 825 men, 541 (66%) with HIV and 284 without HIV. The HIV group was younger (average 49.2 years versus 53 in the HIV-negative group) and had a lower proportion of whites (61% versus 71%) and higher proportions of blacks (30% versus 22%) and Hispanics (9% versus 7%). The HIV group included a higher proportion of current smokers (34% versus 24%) and a lower proportion of former smokers (41% versus 47%). As a group, men with HIV had a lower body mass index and less hypertension and lower "good" high-density lipoprotein cholesterol. A large majority of HIV-positive men (88%) had started antiretroviral therapy, and most had taken antiretrovirals for more than 6 years at the time of the first heart CT scan.
About one third of HIV-positive men and one third of HIV-negative men had coronary artery calcium on their first CT scan. During an average 5 years of follow-up, however, a higher proportion of HIV-positive men than HIV-negative men had newly detected coronary artery calcium (21% versus 16.4%).
In a statistical analysis that considered several heart risk factors at the same time (such as age, race, and smoking), men with HIV had a 64% higher risk of newly detected coronary artery calcium than men without HIV (Figure 1). Current smokers had an 89% higher risk of newly detected coronary artery calcium than men who never smoked. But former smokers did not run a higher risk of newly detected coronary artery calcium than men who never smoked.
Figure 1. A study of 541 U.S. men with HIV and 284 without HIV used coronary artery CT scans to identify factors linked to new development of coronary artery calcium, a heart disease predictor. HIV infection independently raised the risk of new coronary artery calcium 64%. Compared with men who never smoked, current smokers had an 89% higher risk among all men and more than a 100% higher risk (2.26 times higher) in men with HIV. Worse insulin resistance, which can lead to diabetes, raised the coronary artery calcium risk 67% in men with HIV.
Next the researchers focused their statistical analysis only on men with HIV. Regardless of whatever other risk factors an HIV-positive man had, current smoking more than doubled the risk of newly detected coronary artery calcium compared with never smoking (Figure 1). Higher insulin resistance, which can lead to diabetes, raised the risk of newly detected coronary artery calcium 67%. But duration of antiretroviral therapy did not affect chances of newly detected coronary artery calcium in this analysis.
Among 267 men with detectable coronary artery calcium on their first CT scan, 258 of them (97%) had higher (worse) calcium scores through follow-up. Men with HIV did not differ from men without HIV in proportion with worsening coronary artery calcium.
This large study of middle-aged U.S. men found that HIV infection raised the risk of newly detected coronary artery calcium during 5 years of observation. Previous research shows clearly that coronary artery calcium -- which indicates hardening of artery walls -- predicts future cardiovascular diseases like myocardial infarction (heart attack).
This Multicenter AIDS Cohort Study analysis made two other important findings: First, in the overall group of men with and without HIV, current cigarette smokers had a 64% higher risk of new coronary artery calcium than men who never smoked. Former smokers did not run a higher coronary artery calcium risk than men who never smoked. This finding suggests that middle-aged men who stop smoking do not have a higher risk of developing coronary artery calcium than men who never smoked. Looking only at men with HIV, the researchers found that current smoking more than doubled the risk of newly detected coronary artery calcium compared with never smoking.
Second, in men with HIV the study found that higher insulin resistance raised the risk of newly detected coronary artery calcium 67%. Insulin resistance is the inability of body cells to let insulin help them take up glucose from the blood. Insulin resistance can lead to high glucose levels in blood, which can result in diabetes.
These two findings are important because both smoking and insulin resistance can be controlled. Smoking causes not only heart disease, but also lung cancer and other cancers, and serious lung diseases. Quitting is not easy, but lots of people do quit. In fact, the United States has more former smokers than current smokers.3 Talk to your HIV provider about a smoke-ending strategy that will work for you. Nicotine replacement therapy, Chantix, and other medications can help you quit. A national quitline at 1-800-QUIT-NOW (1-800-784-8669) can point you to smoke-ending services in your state.
Your HIV provider can also tell if you have insulin resistance or a high risk of insulin resistance by measuring your blood glucose and insulin. Insulin resistance, high blood glucose, and diabetes can all be prevented or treated. Some of the same strategies to prevent heart disease -- good diet, weight loss, exercise, stopping smoking (Figure 2) -- can also prevent or control high blood glucose and diabetes.
Figure 2. Most factors that raise the risk of heart disease can be controlled or modified, including other medical conditions (left box) and behaviors (middle box). Only a few risk factors cannot be changed (right box). (Source: Centers for Disease Control and Prevention. Heart disease. Heart disease risk factors.)
This large study comparing men with and without HIV and using CT scans recorded over time confirms that HIV-positive people run a higher risk of heart disease than HIV-negative people the same age. People with HIV should be aware of this risk and should work to lower it by living a healthy lifestyle and preventing or controlling the conditions that lead to heart disease.
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