Page last updated at 10:58 GMT, Wednesday, 23 July 2008 11:58 UK

Birth weight 'sets future health'

Baby
Low birth weight has been linked to later problems

Blood vessel changes linked to poor health later in life can be spotted within a few years in boys born small, say scientists.

Eight-year-olds who were smaller at birth were more likely to have "vascular resistance", reported the European Heart Journal.

The Southampton University team said this could contribute to high blood pressure decades later.

However, no such problem was seen in low birth weight girls.

Previous work has linked birth size to later heart disease and diabetes.

Future studies will focus more on childhood in an effort to better understand the processes that lead to disease and to seek to reverse them before it is too late to do anything about it
Dr Alexander Jones
Southampton University

None of the 140 eight or nine year olds tested in this study would showed any actual signs of heart disease, a condition which normally emerges far later in life.

However, scientists believe that even at this age, the arteries of these children may show differences which might raise the risk of problems decades on.

In particular, they tested for how a child's response to stress might affect vascular resistance, a property of blood vessels which makes it harder for the blood to be pumped through,

While vascular resistance does not cause an immediate problem for a child, there is some suggestion that higher levels, particularly if sustained after a stressful event, might increase the chance of blood pressure problems in adulthood.

All the children underwent a public speaking and mental arithmetic test designed to make them nervous, and increase their heart-rate.

Although all the children were in the "normal" range of birth weights, boys at the lower end of the scale were more likely to have higher vascular resistance than those born bigger.

The difference in resistance levels between bigger and smaller birth weight boys was particularly strong half an hour after the test, suggesting some additional difference in the boys' ability to restore normal levels.

Different mechanisms

Girls did not show this effect, but instead had showed different levels of response in the part of their nervous systems linked to the "fight or flight" response.

Dr Alexander Jones, who led the project, said: "The sex differences in these relationships were striking and may eventually lead to a better understanding of why men and women tend to develop high blood pressure and heart or vascular disease at different times in their lives.

"It suggests that different underlying mechanisms for developing the same disorder may exist in the two sexes but have the same eventual result.

"My studies and future studies will focus more on childhood in an effort to better understand the processes that lead to disease and to seek to reverse them before it is too late to do anything about it."

Professor Marjo-Riitta Jarvelin, from Imperial College London, said the findings supported large-scale studies, including one carried out by her own team, which had established the link between birth size and later disease.

"That is beyond doubt now, in my view. There is plenty of evidence that chronic diseases start to develop pre-natally, or at least have their roots in pre-natal life.

"We have supplied the proof that the association exists, now studies such as this one are beginning to look for the mechanism."




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