A new study suggested that a birth weight of 2.5 kg or more is strongly linked to the risk of developing type 2 diabetes in adulthood. The findings of the study were published in the online journal 'BMJ Open Diabetes Research and Care'. The birth weight is associated with lower circulating levels of insulin-like growth factor-1, or IGF-1 for short, a hormone similar to insulin that affects childhood growth and energy metabolism in adults.

Compelling evidence indicated that susceptibility to type 2 diabetes over the life course is determined jointly by risk factors in both early life and adulthood, said the researchers. To find out if there might be any association between adult circulating IGF-1 levels, birth weight, and the risk of developing type 2 diabetes, the researchers drew on data from 112,736 women and 68,354 men taking part in the UK Biobank study.

The UK Biobank is a large population-based study, which recruited its 37 to 73-year-old participants between 2006 and 2010. It is tracking the potential impact of genetic and lifestyle factors on a wide range of common diseases of middle and old age. At recruitment, participants provided social and demographic details, as well as information on their usual diet, lifestyle (smoking status, alcohol intake, sleep duration, and habitual physical activity), early life factors (birth weight and maternal smoking), and medical history.

They also provided blood, urine, and saliva samples, and their height, weight, body mass index (BMI), body circumferences (waist, hip, and limbs), and skinfold thickness were measured. Blood was checked for IGF-1, cholesterol, triglycerides, and an indicator of inflammation, C-reactive protein. And repeat measures of IGF-1 were available from 17,699 participants. Information on the development of type 2 diabetes was obtained from self-report, hospital records, and death certificates.

During an average monitoring period of nearly 10 years, 3299 people developed type 2 diabetes. Participants with lower levels of IGF-1 tended to be older and more likely to live in a deprived area. They were also more likely to have lifestyle and clinical risk factors for diabetes.

Nevertheless, a clear inverse association emerged between IGF-1 levels and type 2 diabetes: the lower the IGF-1 level, the higher was the risk of type 2 diabetes. But birthweight significantly altered this association, although only for those whose weight was 2.5 kg or more at birth, and only in men.

Compared with those in the lowest 20 percent of IGF-1 levels, the odds of type 2 diabetes were 14 percent lower for those in the second-lowest 20 percent, and up to 36 percent lower for those in the highest 20 percent of IGF-1 levels. The findings held, irrespective of any genetic predisposition to birthweight.

This is an observational study, and as such, can't establish the cause. Nor was there any information on whether the births had been premature or full-term, or on ethnicity--factors that may well be influential, say the researchers. Nevertheless, their findings echo those of other epidemiological studies, they note. "Our findings highlight the importance of early-life risk factors in the development of the life course prevention strategies targeting IGF-1 and [type 2 diabetes]," they concluded.