Background: Low birth weight has been associated with an increased risk of type 2 diabetes in adulthood. Poor fetal nutrition has been suggested to explain this association. Our objective was to determine whether genetic factors contribute to the association between low birth weight and subsequent risk of type 2 diabetes.
Methods: We retrieved information from original birth records on same-sex Swedish twins with known zygosity, born from 1926 to 1958. We used regression models to investigate whether birth weight was associated with risk of type 2 diabetes in the cohort of twins overall, and in case-control analyses within disease-discordant dizygotic and monozygotic twin pairs.
Results: Of 18,230 twins, 592 (3.2%) had type 2 diabetes. The rate of type 2 diabetes consistently increased with decreasing birth weight, from 2.4% among twins with birth weights of 3500 g or more to 5.3% among those with birth weights less than 2000 g. In the cohort analysis, in which twins are analyzed as independent individuals, the adjusted odds ratio (95% confidence interval) of type 2 diabetes per 500-g decrease in birth weight was 1.44 (1.28-1.63). When we compared the diseased twin with the healthy cotwin, the corresponding odds ratios were 1.38 (1.02-1.85), among dizygotic twins, and 1.02 (0.63-1.64), among monozygotic twins.
Conclusions: Low birth weight is associated with type 2 diabetes in adulthood. The difference in this association between monozygotic and dizygotic twin pairs suggests that genetic mechanisms play an important role in this association.