The prevalence of insulin resistance in the most common metabolic disorders is still
an undefined issue. We assessed the prevalence rates of insulin resistance in subjects
with impaired glucose tolerance (IGT), NIDDM, dyslipidemia, hyperuricemia, and hypertension
as identified within the frame of the Bruneck Study. The study comprised an age- and
sex-stratified random sample of the general population (n = 888; aged 40-79 years).
Insulin resistance was estimated by homeostasis model assessment (HOMA(IR)), preliminarily
validated against a euglycemic-hyperinsulinemic clamp in 85 subjects. The lower limit
of the top quintile of HOMA(IR) distribution (i.e., 2.77) in nonobese subjects with
no metabolic disorders (n = 225) was chosen as the threshold for insulin resistance.
The prevalence of insulin resistance was 65.9% in IGT subjects, 83.9% in NIDDM subjects,
53.5% in hypercholesterolemia subjects, 84.2% in hypertriglyceridemia subjects, 88.1%
in subjects with low HDL cholesterol, 62.8% in hyperuricemia subjects, and 58.0% in
hypertension subjects. The prevalence of insulin resistance in subjects with the combination
of glucose intolerance (IGT or NIDDM), dyslipidemia (hypercholesterolemia and/or hypertriglyceridemia
and/or low HDL cholesterol), hyperuricemia, and hypertension (n = 21) was 95.2%. In
isolated hypercholesterolemia, hypertension, or hyperuricemia, prevalence rates of
insulin resistance were not higher than that in nonobese normal subjects. An appreciable
number of subjects (n = 85, 9.6% of the whole population) was insulin resistant but
free of IGT, NIDDM, dyslipidemia, hyperuricemia, and hypertension. These results from
a population-based study documented that 1) in hypertriglyceridemia and a low HDL
cholesterol state, insulin resistance is as common as in NIDDM, whereas it is less
frequent in hypercholesterolemia, hyperuricemia, and hypertension; 2) the vast majority
of subjects with multiple metabolic disorders are insulin resistant; 3) in isolated
hypercholesterolemia, hyperuricemia, or hypertension, insulin resistance is not more
frequent than can be expected by chance alone; and 4) in the general population, insulin
resistance can be found even in the absence of any major metabolic disorders.