Classification of Turkish Adults Based on Dyslipidemia and on Lipoprotein Phenotype

Since total/HDL cholesterol ratio (TC/HDL-C) was shown to be one of the best predictors of fatal and nonfatal coronary events among Turks, adu lts as represented in the cohort surveyed in 2000 in the Turkish Adults Risk Factor Study were attempted to be classified herein on the basis of a) dyslipidemia, and b) lipoprotein phenotype. Based on dyslipidemia, for which TC/HDL-C ratio was used, three groups were separated: 1) normoli pideın i c (ratio ~5.0 in men, ~4.5 in women), 2) dyslipideın ic (ratio >5.0 in men, >4.5 in women), of which 3) metabolic syndrome (MS) was differentiated by the concomitant presence of a waist circumference ;:>:94 cm in men, ;:>:80 cm in women, systolic blood pressure ;:>:130 mmHg and of diabetes mellitus or glucose intolerance. As evidence was gathered in the course of the study that the upper normal tirnit for plasma triglycerides would most suitably be 100 mg/di, this limit was used to identify individuals with isolated hypertriglyceridemia and combined h y p erlipide ınia , along with LDL-C >130 ıng/d !. Five categories of lipoprotein phenotype were constructed: a) combined hyperl ipidemia (CHL), b) isolated hypertrig l ycerideınia, c) isolated hyper-LDLcholesteroleınia, d) isolated lo w HDL-C levels ( <35 ıng/di in men, <40 ıng/d i in women), and e) normolipid eınia. In the total cohort of 2414 participants aged 30 years or over, MS and d yslipideınia formed 1.8% and 53% of men and 4.6% and 38% of women, respectively. Dys lip i deınia represented a metabolic defect inasmuch as it d istingu ished itself from the normolipidemic group by a clustering of salient risk factors, namely by an excess of a mean of 2 kg/m2 body mass index (BMI), 3 mmHg of diastolic pressure, 89 mg/di triglycerides, by a reversal of apo Al/apo B ratio whereby apo B value exceeded that of apo AI by 35 mg/di, and in men by an excess of blood fibrinogen (all s ignificant). Though the TC/HDL-C ratio was virtually identical (6.5 vs 6.4), subjects with MS were distinct from dyslipidemia by significantly further elevated levels of triglycerides, BMI and diastolic pressure, in addition to the definition criteria. It was observed that, from a level of I 00 mg/di on w ards, concentrations of HDL-C exhibited clearly inverse trends as triglyceride levels rose, so that the number of individuals with low HDL-C more than doubled, as the limit for triglycerides was shifted upwards from 100 to 140 mg/di. In logistic regression analysis for prevalent coronary heart disease (CHD), dyslipidemia which may largely be considered an incomplete form of MS, did not prove to confer excess risk when compared to normolipidemia, whereas MS doubled the relative risk, even after age adjustment. In the classification by lipoprotein phenotype, CHL was the prominent one, with a prevalence of 22%, underlying 35% of cases with CHD, and being the only independently and significantly associated category with CHD (relative ri sk 1.56, CI 1.05- 2.33). Prevalences in percent of the remaining categories were: isolared hypertriglyceridemia 40%, · isolated hyper-LDL-cholesterolemia 7.3%, isolared low HDL-C levels 2.7%, and normolipidemia 28%. Plasma concentrations of C-reactive protein and apo B were significantly elevated and highest in CHL. It may thus be concluded that, contrasted to Western populations, possessing predominantly high levels of LDL-C, Turkish adults are mainly subjected to the risk arising from atherogenic dyslipidemia.