Objectives To assess the associations of birthweight, contemporary body mass index and height with insulin resistance in children.
Design Cross-sectional study.
Participants From Estonia (n = 1174) and Denmark (n = 1018), 2192 school children aged 9 and 15 years were randomly selected.
Main outcomes Insulin resistance (homeostasis model assessment), triglyceride levels, high-density lipoprotein cholesterol and systolic blood pressure.
Results There was an inverse association between birthweight and insulin resistance and a positive association between contemporary body mass index and insulin resistance. With adjustment for maternal and paternal educational level, income, smoking and body mass index, an increase of one unit of sex, age and country standardized body mass index z-score was associated with a 5% (95% CI: 2, 7%) increase in homeostasis model assessment (HOMA) score and a one-unit z-score increase in birthweight with a 2% (95% CI: 0, 5%) decrease in HOMA score. In the 9-year-old age group, height was positively associated with insulin resistance [for a one-unit increase in height z-score HOMA score increased by 30% (95% CI: 14, 50%)], but in the 15-year-old age group there was no association between height and insulin resistance (4% (95% CI: −5, 14%), P for interaction with age group = 0.001). For both ages, those in the lowest third of the birthweight distribution and highest third of the body mass index distribution were most insulin resistant and, among 9-year olds, those in the lowest third of the birthweight distribution and highest third of the height distribution were most insulin resistant. Birthweight was only inversely associated with systolic blood pressure when adjustment was made for either contemporary body mass index or height and there was no association between birthweight and high-density lipoprotein or triglyceride concentrations.
Conclusions Taken together, these results suggest that a slow intrauterine growth trajectory and/or a fast post-natal growth trajectory is associated with greater insulin resistance in childhood.