Context: Preterm birth is associated with an increased risk of type 2 diabetes in adult life. The mechanisms are poorly known.
Objective: We studied insulin sensitivity and secretion in adults born preterm at very low birth weight (VLBW; < 1500 g).
Design: Longitudinal Birth Cohort Study (Helsinki Study of Very Low Birth Weight Adults).
Setting: The study was conducted at Uusimaa, Finland.
Participants: One hundred seven adults born at VLBW and 100 controls born at term not small for gestational age (SGA), group-matched for sex, age, and birth hospital. The mean age was 25.0 years.
Main outcome measures: We performed a 14-sample intravenous glucose tolerance test and calculated insulin sensitivity (Si), insulin secretory response (AIR), and disposition index, by Minimal Model (Minmod Millennium®).
Results: Compared with controls, VLBW adults had lower Si (mean difference -11.9%, 95% CI -22.1 to -0.4%, adjusted for sex, age, and body mass index) and higher AIR (19.9%; 4.4-37.7%). The association with Si attenuated when further adjusted for height, parental diabetes, parental education, smoking, maternal smoking, hormonal contraception, and physical activity, but the association with AIR remained. Disposition index was similar. There was no difference between the 40 VLBW adults born SGA and the remaining VLBW adults.
Conclusions: Adults born preterm at VLBW have lower insulin sensitivity than their term-born peers with a similar body size. In young adulthood, this remains compensated by higher insulin secretion. We suggest that this represents an early stage in the pathway leading to type 2 diabetes. Our results underline the importance of a healthy lifestyle and prompt vigilance in the screening of type 2 diabetes and impaired glucose tolerance in adults born preterm.