New Findings of the Turkish Heart Study: Guiding Treatment Suggestions for Levels of Plasma Lipids and Low HDL

Turks have unique lipid and lipoprotein profiles characterized especially by low plasma levels of high density lipoprotein cholesterol (HDL-C). The low levels of HDL-C are associated with low levels of the protective subclasses of HDL, HDL2 and LpAI, and with a 25-30% elevation of hepatic lipase activity that would be predicted to lower HDL levels. The widespread occurrence of low HDL-C in Turkey and in Turks living in Germany and the United States suggests that it is at least partly of genetic origin. Turkish children exhibit a marked 10-20 mg/dl drop in HDL-C levels associated with puberty, suggesting that an ethnic difference in hormonal balance contributes to the profoundly low HDL-C levels in adult Turks. Comparison of population data generated in the early 1990s in the original Turkish Heart Study with the present update study of Turkish men and women living in Istanbul indicates that the lipid profile and other risk factors for coronary heart disease (CHD) have not improved in this decade, consistent with the data from the Turkish Society of Cardiology. Despite their relatively low plasma cholesterol levels, Turks have extremely low HDL-C (<40 mg/dl in >70% of men and ~50% of women) resulting in very high total cholesterol/HDL-C ratios that predict increased CHD in other populations. The new National Cholesterol Education Program guidelines continue to focus on low density lipoprotein cholesterol levels and virtually ignore low HDL-C levels, which undoubtedly are a powerful risk factor in Turks. We would suggest that guidelines for Turkey consider low density lipoprotein cholesterol levels and the total cholesterol/HDL-C ratio as thresholds for initiating lifestyle changes or drug treatment for patients with CHD risk.