Prenatal growth, BMI, and risk of type 2 diabetes by early midlife

OBJECTIVE - Small size at birth has been associated with increased risk of type 2 diabetes. Our aim was to evaluate how risk of diabetes associated with low birth weight is affected by accumulation of body mass from childhood to adulthood. RESEARCH DESIGN AND METHODS - Subjects from the 1958 British birth cohort (born 3-9 March 1958) have been followed regularly since birth. In the survey at 41 years of age, 88 participants reported type 2 diabetes (n = 10,683). RESULTS - Participants in whom diabetes developed weighed less at birth and had higher BMIs than the others. Birth weight (adjusted for gestational age and sex) was inversely related to risk of diabetes (odds ratio for 1-SD change 0.76, 95% CI 0.56-0.99). All diabetic participants in the lowest third of birth weight were in the highest third of weight gain by 23 years of age. An increased risk of diabetes was found for those in the lowest third of BMI at 7 years of age (2.84, 1.2-6.9), but diabetic participants in this group had excessive weight gain to 23 years of age All but one diabetic participant in the highest third of childhood BMI remained in the highest third until 23 years of age. Risk of diabetes by BMI at 23 years of age was 22.9-fold (95% Cl 12-42) for obese participants and 3.8-fold (2.1-6.9) for overweight participants compared with those of normal weight. CONCLUSIONS - There was no increase in risk of diabetes for small size at birth without excessive postnatal weight gain. Adult obesity was the most important risk factor for type 2 diabetes developing by early midlife.