OBJECTIVE To determine whether the features of syndrome × are more common in first-degree relatives of non-insulin-dependent diabetes mellitus (NIDDM) patients than in control subjects with no family history of diabetes.

RESEARCH DESIGN AND METHODS A total of 154 first-degree relatives from 60 families with two or more NIDDM patients and 154 age- and sex-matched control subjects were studied. All subjects underwent a 75-g oral glucose tolerance test and baseline lipid blood and anthropometric measures. The features of syndrome × that were studied were obesity, hypertension, dyslipidemia (high triglyceride levels and low high-density lipoprotein [HDL] cholesterol concentrations), impaired glucose tolerance (World Health Organization criteria), and insulin resistance (as assessed by the homeostasis model assessment).

RESULTS Relatives were heavier than control subjects (body mass index 27.5 ± 5.2 vs. 25.2 ± 4.6 kg/m², respectively [mean ± SD], P < 0.0002), had lower HDL cholesterol concentrations (1.2 ± 0.3 vs. 1.4 ± 0.4 mmol/l, P < 0.001), were more insulin-resistant (2.3 [0.7−7.6] vs. 1.6 [0.5−5.1], geometric mean [95% confidence intervals], P < 0.0001), and had more individuals classified as having impaired glucose tolerance (28 of 154 [18%] vs. 7 of 154 [7%], χ 2, P < 0.001). The differences in insulin resistance and HDL cholesterol concentrations between the groups were independent of obesity.

CONCLUSIONS Features of syndrome X occur more frequently in relatives of NIDDM patients than in control subjects with no family history of diabetes.