[Serum insulin distribution and the relationship between environmental factors and serum insulin levels in a Japanese urban population].

An epidemiological study was conducted to investigate the distribution of serum insulin and the relation of environmental factors to serum insulin concentrations in an urban population. In 1992 and 1993, 75 g oral glucose tolerance tests (OGTT) were performed and serum insulin concentrations determined for 2,147 subjects aged 30 to 79, randomly selected from residents of S-city in Osaka Prefecture. The subjects had received a health examination for cardiovascular disease at the National Cardiovascular Center. Median values of area under the insulin curve (AUIC), which is an index of insulin resistance, were similar for men and women, but were higher for older than younger women. Sex and age specific estimated upper limits of AUIC were set at the 95 percentile level of AUIC for the subjects without a history of stroke or myocardial infarction, and who did not have diabetes mellitus, obesity, hypertension, or dyslipidemia. Prevalence of hyperinsulinemia in the subjects was about 10 to 16%. The sex and age specific proportion of obesity, hypertriglyceridemia, hypo-HDL-cholesterolemia, and hypertension was higher for hyperinsulinemic than normoinsulinemic subjects. Relation of AUIC to obesity, dietary intake, physical activity, alcohol consumption, cigarette smoking, and antihypertensive drug use was examined in 2,039 subjects who were diagnosed as non-diabetic by OGTT. Of the environmental factors analysed, body mass index alone correlated independently with AUIC for all sex and age specific classes. For men aged 30 to 59 the waist/hip ratio correlated independently and positively with AUIC. This indicates that control of obesity, especially of upper-body obesity or visceral type obesity, should be considered important for improvement of insulin resistance.