Apparent protective effect of high density lipoprotein against coronary heart disease in the elderly

BACKGROUND: This study was designed to evaluate the relationship between high-density lipoprotein cholesterol (HDL-C) level and acute myocardial infarction (AMI) and coronary heart disease (CHD) death and to explore the protective effect of HDL against CHD in the elderly Chinese. METHODS: Started from 1986, 1211 retirees (92% males) were enrolled consecutively and studied prospectively. The average starting age was 70 +/- 9 years, and that at the end of the study was 80 +/- 9 years. During the follow-up study, all the participants received yearly physical examination and blood chemistry survey from 1986 - 2000. The average duration of the follow up study was 11.2 years. The end point of this study was either attacks of AMI or death due to CHD and other causes. CHD risk factors were screened by logistic regression analysis. According to their HDL-C levels, cases were divided into low (< 1.03 mmol/L), medium (or normal, 1.03 - 1.56 mmol/L) and high (> 1.56 mmol/L) level groups, the differences in incidence of AMI and CHD death in each group were analyzed. RESULTS: The cumulative attacks of acute coronary syndrome (mostly AMI) were 214 cases, including 89 cases of coronary death and 308 death caused by other diseases during the follow up study. AMI occurrence and CHD death in normal HDL-C group were lower than those in the low HDL-C group by 40% and 53%; and those in the high HDL-C group were lower than in the normal group by 56% and 50%, respectively. Statistical analysis on normal lipid cases (411 cases, total cholesterol < 5.17 mmol/L, triglyceride < 1.69 mmol/L) revealed that the cases at low HDL-C level had similar rates of AMI events and CHD mortality as those of the entire group (including hyperlipidemia); however, AMI attacks and CHD deaths decreased significantly at the normal and high HDL-C levels. The results demonstrated that the protective effect of HDL against coronary artery disease is more prominent in people with low lipid level. CONCLUSION: Low HDL is an important independent risk factor for AMI attacks and CHD death in the elderly; high HDL has significant protective effect against coronary artery disease.