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

To evaluate the relationship between the level of high-density lipoprotein cholesterol (HDL-C) and acute myocardial infarction (AMI) events and coronary heart disease (CHD) death, and to explore the protective effect of high level HDL against CHD in the elderly Chinese.

A prospective study was done upon 1211 retired cadres, 92% of which were males, enrolled in succession since 1986, aged 70 +/- 9 on average when being enrolled and aged 80 +/- 9 on average by the end of the study. During a follow up study with an average duration of 11.2 years, till the year 2000 or a specific subject died of CHD or other disease, all the participants received yearly physical examination and blood chemistry survey. CHD risk factors were screened by logistic regression analysis. According to their HDL-C levels, the subjects were divided into 3 groups: low HDL-C (< 1.03 mmol/L), medium HDL-C (1.03 - 1.56 mmol/L), and high HDL-C (> 1.56 mmol/L) groups. The differences in AMI event and CHD death in each group were analyzed.

411 of the subjects were with normal blood lipid (normal blood lipid group, total cholesterol < 5.17 mmol/L, triglyceride < 1.69 mmol/L), 338 subjects were basically healthy (basically healthy group), and 214 subjects developed CHD during the follow-up (CHD group). 23.2% of the subjects could be included in the low HDL-C group, 68.7% in the medium HDL-C group, and 68.5% in the high HDL-C group. The low HDL-C rate was 16.9% in the basically healthy group and 35.0% in the CHD group (P = 0.000165). The high HDL-C rate was 12.4% in the basically healthy group and 3.3% in the CHD group (P = 0.000645). During the follow up study, 214 cumulative attacks of acute coronary syndrome (mostly AMI) were recorded with 89 deaths. 308 cases died of other diseases. The AMI event rate and CHD death rate in the normal HDL-C group were lower than those in the low HDL-C group by 40% and 53% respectively. The AMI event rate and CHD death rate in the high HDL-C group were lower than those in the normal HDL-C group by 56% and 50% respectively. In the normal lipid group, AMI event rate and CHD mortality in the individuals with low HDL-C level were lower than those in the individuals with medium HDL-C level by 79% and 77% respectively (both P < 0.0001). The number of individuals with high HDL-C level was low, however, no CHD death occurred among these subjects.

Low HDL is an important independent risk factor of AMI attacks and CHD death in the elderly. High HDL protects effectively against coronary artery disease. High TC level weakens the protective effect of HDL-C.