Do total and high density lipoprotein cholesterol and triglycerides act independently in the prediction of ischemic heart disease? Ten-year follow-upof caerphilly and speedwell cohorts

Several studies have suggested that men with raised plasma triglycerides (T Gs) in combination with adverse levels of other lipids may be at special ri sk of subsequent ischemic heart disease (EHD). We examined the independent and combined effects of plasma lipids at 10 years of follow-up. We measured fasting TGs, total cholesterol (TC), and high density lipoprotein choleste rol (HDLC) in 4362 men (aged 45 to 63 years) from 2 study populations and r eexamined them at intervals during a 10-year follow-up. Major IHD events (d eath from rHD, clinical myocardial infarction, or ECG-defined myocardial in farction) were recorded. Five hundred thirty-three major IHD events occurre d. All 3 lipids were strongly and independently predictive of IHD after 10 years of follow-up. Subjects were then divided into 27 groups (ie, 3(3)) by the tertiles of TGs, TC, and HDLC. The number of events observed in each g roup was compared with that predicted by a logistic regression model, which included terms for the 3 lipids (without interactions) and potential confo unding variables. The incidence of IHD was 22.6% in the group with the lipi d risk factor combination with the, highest expected risk (high TGs, high T C, and low HDLC) and 4.7% in the group with the lowest expected risk (P <0. 01). A comparison of the predicted number of events in the 27 groups with t he number of events observed showed that a logistic regression provided an adequate fit without the need to incorporate interactions between lipids in the model. Conclusions are as follows: (1) Serum TGs, TC, and HDLC are ind ependently predictive of IHD at 10 years of follow-up. (2) Combinations of adverse levels of the 3 major lipid risk factors have no greater impact on IND than that expected from their individual contributions in a logistic re gression model. There was no evidence that men with low HDL/raised TGs were at significantly greater risk than that predicted from the independent eff ects of the 2 lipids considered individually.