Fainting episodes hereditary



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Do genes determine susceptibility to fainting?

The vulnerability to fainting is apparently genetically determined. The research team led by Samuel Berkovic from the Epilepsy Research Center at the University of Melbourne has found that genetic factors have a significant impact on the occurrence of so-called syncope (fainting due to circulatory collapse).

Although the scientists were unable to identify a single gene that could be responsible for the increased susceptibility to fainting, they used twins to demonstrate that genetic factors play a major role in overall loss of consciousness. Fainting is at least partly hereditary.

Identical twins with similarities in fainting susceptibility In the course of their study, the researchers led by Samuel Berkovic surveyed 51 same-sex twin pairs, of which at least one twin had already fainted. The age of the subjects was between nine and 69 years. The twins were interviewed by phone using a standardized questionnaire and the available medical records were also analyzed. The researchers observed a clear "trend towards case-by-case higher matches in monozygous (monozygotic) than in dizygotic (dizygotic) twins for each syncope," Berkovic and colleagues report in the journal "Neurology". In identical situations, the neurologists write that the likelihood of one twin losing consciousness is also twice as high for genetically identical (monozygotic) twins as for dizygotic.

Several genes cause the increased susceptibility to fainting. In general, the identical twins had a far clearer agreement regarding fainting fits than the dizygotic. This suggests that "impotence is genetic, but there may be multiple genes and multiple environmental factors that trigger the phenomenon," said Berkovic and colleagues in the article, "Evidence of Genetic Factors in Vasovagal Syncope" . Overall, the analysis of the twin pairs delivers "strong evidence of the importance of genetic factors" when sudden fainting occurs. It was also striking that twelve of the 19 identical pairs of twins indicated that little or no other family members were affected by fainting spells, while in the remaining seven pairs of twins, several close relatives also suffered syncope. The researchers evaluated this as an indication that several genes presumably cause the vulnerability to fainting. “If it were a single gene, one might expect,” says Samuel Berkovic, “that the fainting frequency of other relatives of the twins is similarly high.” However, the researchers did not find this out.

Fainting due to insufficient blood flow to the brain Vasovagal syncope are neural, whereby a reflex causes the sudden enlargement of the blood vessels and a decrease in the heart rate. The result is a sudden drop in blood pressure and insufficient blood flow to the brain. Those affected lose consciousness for a short time and collapse. When lying down enough blood reaches the brain again, so that the fainting is usually over after a short time. Nevertheless, the situations for those affected are often extremely uncomfortable and often dangerous. Possible causes of this sudden fainting can be, for example, acute stress, the sight of blood, horror, pain or standing for a long time. (fp)

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