Low birthweight and overweight during childhood and young adulthood and the risk of type 2 diabetes in men: a population-based cohort study

Aims/hypothesis This study aimed to determine the relative contributions of low birthweight and overweight during childhood and young adulthood to the risk of type 2 diabetes in men. Methods We included 34,231 men born between1945 and 1961 from the population-based BMI Epidemiology Study (BEST) Gothenburg with data on birthweight and overweight status in childhood (8 years, BMI >17.9 kg/m(2)) and young adulthood (20 years, BMI >25 kg/m(2)). Participants were followed from age 30 years until 31 December 2019. Information on type 2 diabetes diagnoses was retrieved from Swedish national registers. HRs and 95% CIs for the risk of early (<= 59.4 years) and late (>59.4 years) type 2 diabetes were estimated using Cox proportional hazards regression. Results During follow-up, a total of 2733 cases of type 2 diabetes were diagnosed. Birthweight below the median (<3.6 kg) and overweight at age 20 (BMI >25 kg/m(2)), but not overweight at age 8 (BMI >17.9 kg/m(2)), were associated with an increased risk of early and late type 2 diabetes. Of note, a birthweight below the median followed by overweight at age 20 years was associated with a substantially increased risk of early type 2 diabetes (HR 6.07, 95% CI 5.08, 7.27), and a low birthweight (<= 2.5 kg) combined with overweight at age 20 years was associated with a massive risk of early type 2 diabetes (HR 9.94, 95% CI 6.57, 15.05). Conclusions/interpretation Low birthweight and overweight in young adulthood are the major developmental determinants of adult type 2 diabetes risk in men. They contribute in an additive manner to the risk of type 2 diabetes. To reduce the risk of type 2 diabetes, young adult overweight should be avoided, especially in boys with a low birthweight.