Abstract 1280: Differences in Characteristics and Outcomes by High-Density Lipoprotein Cholesterol Levels: The Intermountain Heart Collaborative Study
Background: Very low (<20 mg/dL) and low (20–39 mg/dL) levels of high-density lipoprotein cholesterol (HDL), when compared with normal (40– 69 mg/dL) levels, are associated with an increased risk of coronary artery disease (CAD). However, whether very high (>70 mg/dL) levels of HDL, which might suggest a different mechanism of production, also provide cardiovascular protection is not known. To address this question, we evaluated the association of HDL levels with important characteristics and outcomes.
Methods: Patients (N=17,323) undergoing angiographic evaluation for coronary artery disease (CAD) with an HDL measurement were studied. Patients were categorized into very low (n=341), low (n=8,778), normal (n=6,916) and very high (n=611), by baseline HDL level. Cox regression models adjusting for standard CAD risk factors were used to assess the incidence of myocardial infarction (MI) and death (average follow-up: 4.5±3.6 years) by HDL category.
Results: Significant (all p<0.0001 except age [p=0.006]) differences in characteristics among HDL categories were: When compared to normal, low and very low HDL levels were associated with CAD and very high levels were protective: very low=69.5%, low=66.3%, normal=49.7%, high=34.9% (p<0.0001). Very low HDL levels were associated with a follow-up MI (vs. very low [adjusted]: low: HR=0.77, p=0.05, normal: HR=0.61, p<0.0001, high: HR=0.62, p=0.03). However, HDL level did not predict death (vs. very low [adjusted]: low: HR=0.87, p=0.13, normal: HR=0.86, p=0.10, very high: HR=1.09, p=0.59).
Conclusions: In this large population being evaluated for CAD, significant differences in baseline characteristics and cardiac risk factors were found among HDL levels. Similar to normal levels, even very high levels of HDL were protective for angiographic CAD and incident MI. The paradoxical absence of predictive value of HDL on death deserves further study.