Relation between birth weight and the insulin sensitivity index in a population sample of 331 young, healthy Caucasians.

The objective was to study the association between birth weight and the insulin sensitivity index. Altogether, 331 unrelated Caucasian subjects aged 18-32 years with measures of the insulin sensitivity index and insulin secretion during a combined intravenous glucose and tolbutamide tolerance test were included in the study. The data on birth weight and length were obtained from the midwife records. The study took place in Copenhagen, Denmark, during 1992-1993. Univariately, a significant positive association between birth weight and the insulin sensitivity index was found in women (p = 0.045), but not in men (p = 0.23). In multivariate analysis, controlling for age, gender, body mass index, waist circumference, maximal aerobic capacity, and use of oral contraceptives, no significant interaction between birth weight and gender that considered the insulin sensitivity index was found. The insulin sensitivity index was significantly associated with birth weight (p = 0.0012), corresponding to an increase of 1.7% (95% confidence interval 0.7-2.7%) in the insulin sensitivity index for each 100-g increases in birth weight. In comparison, an increase in body mass index of 1 kg/m2 (a weight gain of 2.9 kg in a man 1.70 m tall) corresponds to a decrease in the insulin sensitivity index of 3.8% (95% confidence interval 0.7-6.8%), an increase in waist circumference of 1 cm corresponds to a decrease in the insulin sensitivity index of 2.1% (95% confidence interval 0.9-3.1%), and use of oral contraceptives corresponds to a decrease in the insulin sensitivity index of 26.7% (95% confidence interval 12.2-38.1%). Thus, the impact of birth weight on the insulin sensitivity index was of minor importance.