New research underlines link between lower birth weight and heart disease in later life
Southampton researchers have found the first evidence that children who were smaller at birth already have specific alterations in heart and blood vessel function in early childhood, which may help to explain why they are more likely to develop heart disease in later life.
The research, led by Dr Alexander Jones, a clinical research fellow at the University of Southampton’s MRC Epidemiology Resource Centre, is published today in Europe’s leading cardiology journal the European Heart Journal.
The study’s findings add to growing evidence that suggests the way the heart and blood vessels function during stress reveal individual characteristics associated with a higher risk of hypertension (high blood pressure) and disease of the heart and blood vessels.
Studies of 140 children aged eight and nine who underwent a psychological stress test also revealed that the changes in the heart and circulation differed between boys and girls.
The children had been healthy babies, born in Southampton, and were within the normal birth weight range.
They were asked to perform a public-speaking task involving storytelling, followed by mental arithmetic. During this the performance of their heart and circulation was recorded using electrical sensors.
Dr Jones, who is now a clinician scientist at the UCL Institute of Child Health in London, said: “In boys we found that the lower their birth weight was, within the normal range, the more likely they were to have a higher vascular resistance – the resistance to flow that has to be overcome to push blood around the circulatory system – and higher blood pressure, particularly 25-30 minutes after the start of the stress test.
“In contrast, girls who were smaller at birth did not demonstrate a specific response to stress. They consistently, whether under stress or at rest, showed evidence of greater activity in the sympathetic nervous system – the part of the nervous system that controls involuntary actions and becomes more active during stress contributing to the ‘fight or flight’ response.
“This is the first evidence of relationships between size at birth and the function of the heart and blood vessels in childhood. 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.”
While the changes in the children’s responses to stress did not show that they had any early indications of disease, Dr Jones said: “We have strong reasons to believe that children with more exaggerated stress responses are more likely to become adults who develop hypertension and go on to develop heart or vascular disease earlier in life than those who do not demonstrate these greater responses.”
A strength of the study was that it was carried out in young children before puberty when it was unlikely that any disease processes would have started that might alter the results – unlike the situation in adults. “Thus, we can be more confident that the differences we are finding represent the very early indicators of processes that underlie later disease,” said Dr Jones.
“By highlighting these specific heart and circulatory changes in the developing child, we may, in the future, be able to develop interventions that target the origins of heart and circulatory diseases. These diseases are the world's biggest killers but their causes are still poorly understood and the vast majority of medical attention is given to their palliation once they have already occurred. I believe 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.”
Notes for editors
It is nearly twenty years since Professor David Barker at the University of Southampton established the theory that people with low birth weight are at greater risk of developing coronary heart disease. His research went on to indicate that they are also at greater risk of stroke, high blood pressure and type-2 diabetes. This led to the idea that these disorders originate through under-nutrition in the womb and during infancy. In 1992, the British Medical Journal named this the Barker Hypothesis, and it is now widely accepted.