A study of nearly 6000 elderly people in Birmingham has shown that ‘hidden’ thyroid disorders are common in over-65s and that there is a strong link between one type of abnormality and irregular heartbeat. The work will be presented at the British Endocrine Societies 2005 meeting in Harrogate on Wednesday.
The Birmingham Elderly Thyroid Study (BETS) run by the University of Birmingham (and funded by the Health Foundation) screened 5784 subjects over the age of 65 with no history of known thyroid problems. By measuring levels of different hormones the study found that more than 1 in 20 showed evidence of 'hidden' thyroid disorders, i.e. the biochemical tests revealed mildly abnormal thyroid function even though the individual had no obvious symptoms - known by doctors as 'sub-clinical' disorders.
Tests of 2.2% of the subjects showed up a mildly overactive thyroid, known as sub-clinical hyperthyroidism. More than one in ten people in this group had an irregular heartbeat - or atrial fibrillation, AF - a risk factor for stroke and heart disease. This compares to less than one in twenty of those with normal thyroid function showing AF.
Links between sub-clinical hyperthyroidism and atrial fibrillation have previously been reported. This is the first study to look at subjects with no known previous history of thyroid problems e.g. those taking replacement thyroid hormone or previously treated for an obviously overactive thyroid.
Other ongoing elements of the study are looking at the link between hypothyroidism and cognitive function.
Jayne Franklyn, one of the Study’s researchers and a Professor in the Division of Medical Sciences at the University of Birmingham, said ‘Sub-clinical thyroid disorders are common in the elderly, and we have found further strong evidence that these can have serious health consequences. However, it is currently unclear whether treating a mildly overactive thyroid would prevent the development of atrial fibrillation. We urge that large trials be supported to see if this sort of thyroid treatment can benefit heart-health in the elderly.’