Background: A large and consistent body of evidence supports the judgment that elevation of total plasma blood cholesterol is a cause of myocardial infarction (MI) and that high levels of low density lipoprotein (LDL) cholesterol have a positive relation and high levels of high density lipoprotein (HDL) cholesterol an inverse relation with MI. At present, however, the roles, if any, of the major subfractions of HDL, namely, HDL2 and HDL3, have not been clarified. In addition, the relation of plasma apolipoprotein concentrations to MI and whether they provide predictive information over and above their lipoprotein cholesterol associations is unknown.
Methods and results: We evaluated these questions in a case-control study of patients hospitalized with a first MI and neighborhood controls of the same age and sex. Cases had significantly lower levels of total HDL (p less than 0.0001) as well as HDL2 (p less than 0.0001) and HDL3 (p less than 0.0001) cholesterol. These differences persisted after controlling for a large number of demographic, medical history, and behavioral risk factors and levels of other lipids. There were significant (p less than 0.0001) inverse dose-response relations with odds ratios for those in the highest quartile relative to those in the lowest of 0.15 for total HDL, 0.17 for HDL2, and 0.29 for HDL3 cholesterol levels. Levels of LDL and very low density lipoprotein cholesterol and triglycerides were also higher among cases than controls, but only for triglycerides was the difference statistically significant after adjustment for coronary risk factors and other lipids (p = 0.044). Apolipoproteins A-I and A-II were both significantly (p less than 0.0001) lower in cases, and differences remained even after adjustment for coronary risk factors and lipids. There were significant dose-response relations for both apolipoprotein A-I (p = 0.026) and A-II (p = 0.002). Neither apolipoprotein B nor E was significantly related to MI after adjustment for lipids and other coronary risk factors. When all four apolipoproteins were taken together, there was an increased level of prediction of MI over the information provided by the lipids and other coronary risk factors (p = 0.003), but this appeared present only for the individual apolipoproteins A-I (p = 0.027) and A-II (p = 0.011).
Conclusions: These data indicate that both HDL2 and HDL3 cholesterol levels are significantly associated with MI. They also raise the possibility that apolipoprotein levels, especially A-I and A-II, may add importantly relevant information to determination of risk of MI.