The prevalence of metabolic syndrome is high among HIV-positive individuals, but not higher than the prevalence among HIV-uninfected individuals. This new study conclusion, published by researchers at the Washington University School of Medicine in the March 1 issue of Clinical Infectious Diseases, suggest that traditional risk factors play a more significant role in the development of metabolic syndrome in people with HIV than do antiretroviral-related factors.
According to the National Heart, Lung, and Blood Institute's National Cholesterol Education Program (NCEP), the metabolic syndrome is defined as a cluster of conditions – including abdominal obesity, high blood sugar, and lipid problems (e.g., high triglycerides and and low HDL ["good"] cholesterol) – that can lead to diabetes and cardiovascular disease.
While not an HIV-specific condition, there is no shortage of data from studies showing that HIV-positive people receiving antiretroviral treatment are at risk for the metabolic syndrome. Protease inhibitors in particular have been associated with an increased risk of cardiovascular disease and diabetes, possibly in part because of their negative effects on glucose and lipid levels in the blood.
While reported prevalence rates of metabolic syndrome have been higher among HIV-positive patients on antiretroviral therapy compared to HIV-positive patients not on treatment, studies have also concluded that these rates are similar to, or even less than, the 22% to 24% rate of prevalence reported recently for the general U.S. population. This has some experts suggesting that the increased prevalence of metabolic syndrome among HIV-positive patients may have more to do with the burgeoning obesity epidemic than a predominant effect of antiretroviral therapy.
To explore this theory further, researchers at the Washington University School of Medicine reviewed the medical records of 471 HIV-positive patients who attended the Washington University HIV Clinic in St. Louis between January and July 2005 and compared them to 471 HIV-negative individuals of the same age, sex, race, and history of tobacco use participating in the National Health and Nutrition Examination Survey (NHANES).
Approximately 69% of the HIV-positive patients were receiving antiretroviral therapy. Approximately 77% of the patients on antiretroviral therapy had viral loads below 400.
The overall prevalence of metabolic syndrome was similar between the group of HIV-infected patients and the HIV-negative controls (25.5% vs. 26.5%, respectively). Using the Framingham cardiovascular disease risk calculator, the researchers also determined that the ten-year risk of heart attacks was similar in the HIV-positive patients and the HIV-negative NHANES participants.
"For the patients in the HIV-infected cohort," the authors write, "traditional risk factors (e.g., older age and higher BMI), higher CD4 cell count, and white race were the strongest predictors of the presence of the metabolic syndrome." As for the use of antiretroviral therapy, "Unexpectedly," the researchers add, "the duration and type of [HIV treatment] were not strong predictors."
Among HIV-related factors, although a higher CD4 cell count was an independent predictor of the development of metabolic syndrome, a higher body mass index accounted for a substantial part of this CD4-attributable risk. This, the authors suggest, may be tied to the expected increase in body weight and improved nutritional and immunologic status that coincides with effective HIV treatment.
"In the general U.S. population," the authors write, "epidemic rates of obesity, insulin resistance, hypertension, and associated complications have been noted in recent years. The current findings suggest that HIV-infected persons treated with [antiretroviral therapy] are not spared from this emerging epidemic," as demonstrated by their high rates of obesity, high glucose levels, high blood pressures, and lipid problems. "These findings, along with a lack of independent effects of [antiretroviral therapy] on metabolic syndrome, support the notion that these traditional risk factors may be more important than [antiretroviral therapy]-related factors for the prediction of metabolic syndrome and cardiovascular disease risk."
Source:
Mondy K, Overton ET, Grubb J, et al. Metabolic syndrome in HIV-infected patients from an urban, Midwestern US outpatient population. Clin Infect Dis 44:726-34, 2007.
