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Monday, 7 January, 2002, 00:03 GMT
Dyslexia blood pressure 'link'
blood pressure
Dyslexia could be linked to low blood pressure
Many dyslexic children come from families with a history of lower blood pressure - adding weight to theories of a common cause of the disorder.

The origins of the learning disability - which causes children to have poor reading skills - are a mystery to doctors.

To our knowledge, no other hypothesis of developmental dyslexia has made this particular prediction or has proposed mechanisms which could explain this finding.

Report authors
It has been suggested that as many as 10% of UK children may suffer from dyslexia in some form.

And many doctors believe that its cause is at least partly due to physical differences in the brain.

One possibility is that dyslexics have too much of a particular body chemical called phospholipid platelet activating factor (PAF)

Blood vessel function

Phospholipids are a type of "fatty acid" which are a vital component of the cell membrane - they have a role in chemical signalling between cells, the function of the immune system.

One of the functions of PAF is to expand blood vessels, causing a fall in blood pressure.

Scientists at Oxford University's Laboratory of Physiology decided to test the theory by seeing whether there was a correlation between dyslexic children and lower blood pressure in their families.

They looked at 112 children aged between six and 18, all of whom were diagnosed dyslexics.

Another 12 children without the condition also joined the study.

Further study

Among the dyslexic children, 49 came from families affected by high blood pressure - but 63 came from families with no such history.

Virtually all the non-dyslexic children had some history of high blood pressure in their families - a much higher proportion than the dyslexic children.

In addition, an examination of the children who came from high blood pressure families found they performed better on number recall, reading and spelling, all tasks which dyslexic children find difficult.

The study does not provide conclusive evidence of the link, say the scientists, perhaps due to the small numbers of children involved, but they are hoping to construct a larger one to further test their theory.

However, they say that it adds further weight to the theory that PAF is somehow involved in both dyslexia and lower blood pressure.

They wrote: "To our knowledge, no other hypothesis of developmental dyslexia has made this particular prediction or has proposed mechanisms which could explain this finding."

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