Babies born early may have a small increased risk of diabetes when they grow up, a Swedish study says.
Children born before 37 weeks had a slightly higher risk - less than 1% higher - of developing diabetes at some point in their life, according to the online paper in Diabetes Care.
Doctors need to "recognise that pre-term birth is a risk factor for diabetes in later life," Dr Casey Crump of Stanford University in California said.
People born prematurely risk diabetes
And for people born prematurely, "it's even more critical" to avoid other risk factors for diabetes, said Dr Crump, who co-authored the study.
The study was done in Sweden, but the findings could have a large public health impact elsewhere, too, Dr Crump said. In the US, for instance, the Centres for Disease Control and Prevention (CDC) in Atlanta estimate that three of every 25 babies are delivered prematurely.
The researchers used a national prescription database to track the use of diabetes medications by roughly 630,000 people born in Sweden between 1973 and 1979. Roughly 28,000 of those were born prematurely.
Dr Crump's team found that about 15 out of 1000 preemies had diabetes by the time they were in their twenties and thirties, compared to about 12 of 1000 full-term babies.
The increased risk of diabetes applied not only to people who were born very prematurely, but also those born just a week or two early.
The researchers don't have a good explanation yet for why early birth might be linked with later diabetes. Dr Crump points out that poor nutrition, either in the womb or right after birth, can trigger changes in the baby's hormones or metabolism that can lead to abnormal processing of blood sugar, which might increase the risk of diabetes later. The current study didn't look at preemies' nutritional status, however.
In general, diabetes is less common in Sweden than in the US, where it affects about 17 out of every 1000 people in the 25 to 35 age group, Dr Crump said. Also, the rate of premature births in Sweden is about a third of the rate in the US.
Risk factor for diabetes
But Dr Crump points out that premature birth is not as important a risk factor for diabetes as obesity and family history.
"I think prematurity is more of a problem in more deprived communities, and that is also the population in which you see more obesity," said Dr Caroline Fall, professor of international paediatric epidemiology at the UK's University of Southampton.
People who were premature "need to pay a little more attention than people who were not" to take steps to prevent diabetes, Dr Fall, who was not involved in the study, said.