A low level of high-density lipoprotein cholesterol (HDL-C) has been considered to be a cardiovascular (CV) risk factor. In fact, a 1% increase in HDL-C leads to a 2–3% decrease in the risk of coronary artery disease (CAD), said Sergio Nabais-Araujo, MD, Hospital S. Marcos, Braga, Portugal.

Prof. Nabais-Araujo presented study findings in which the association between HDL-C level and outcomes was evaluated in 944 patients with acute coronary syndrome (ACS). The patients were assigned to one of two groups based on their baseline HDL-C level (within 24 hours of admission to the coronary care unit). High HDL-C was defined as ≥40 mg/dL for men and ≥45 mg/dL for women; low HDL-C was defined as <40 mg/dL for men and <45 mg/dL in women. High HDL-C level was associated with a lower rate of the composite endpoint of death, MI, and recurrent ischemia at 6 months (18.6% vs 24.3%; p=0.037). However, mortality at 30 days and 6 months was similar for the two groups of patients.

The cardioprotection conferred by an elevated level of HDL-C is thought to be related to anti-inflammatory effects. In a hypothesis-generating study presented by Demosthenes Panagiotakos, MD, University of Athens, Greece, the relationship between HDL-C and several anti-inflammatory markers was evaluated in a population of 2,282 men and women who were free of cardiovascular disease. Prof. Panagiotakos reported that there was a significant inverse correlation between levels of HDL-C and levels of high-sensitivity C-reactive protein (p=0.001) and homocysteine (p=0.036), after adjustments were made for several demographic variables. No significant relationship was found between HDL-C levels and interleukin-6 and serum amyloid A levels.

Another marker of CV risk is the ratio of total cholesterol (TC) to HDL-C; a ratio of 4 or more has been associated with increased risk for ACS. Deepu Nair, MD, Cleveland Clinic, Ohio, and colleagues assessed the association between the TC/HDL-C ratio and evidence of disease in the proximal coronary arteries (the site of most atherosclerotic ruptures) on multislice computed tomography. Dr. Nair reported that in 281 individuals with documented CAD, the prevalence of proximal plaque was significantly higher in individuals with a TC/HDL-C ratio of 4 or more (62% vs 48%; p=0.02). The prevalence of proximal stenosis was also significantly higher in this group of patients (20% vs 8%; p=0.003). He suggested that an elevated TC/HDL-C ratio defines a group of patients at higher risk for ACS.

The results of these studies indicate that enhanced efforts to increase the HDL-C level and to decrease the TC/HDL-C ratio may be of benefit, especially in individuals with ACS or at high risk for the disease; the cardioprotection offered by HDL-C stemming from its direct relationship with anti-inflammatory markers.