Fainting fits hereditary

Determine genes susceptibility to fainting?

08/07/2012

The susceptibility to fainting appears to be genetically conditioned. The research team led by Samuel Berkovic from the University of Melbourne Epilepsy Research Center has found that genetic factors have a significant impact on the occurrence of syncope (fainting through circulatory collapse).

While scientists could not identify a single gene that could be considered more susceptible to fainting, they identified by means of twins that genetic factors play a key role in overall loss of consciousness. According to this, fainting is at least partially hereditary.

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

Several genes cause the increased susceptibility to fainting
In general, the identical twins had far greater agreement with regard to the fainting spells than with the twins. This suggests that "fainting is genetically conditioned, but there may well be several genes and multiple environmental factors that trigger the phenomenon," Berkovic and colleagues said in the article "Evidence of genetic factors in vasovagal syncope." , Overall, the analysis of the twin pairs provides "strong evidence of the importance of genetic factors" in the occurrence of sudden fainting. It was also striking that twelve of the 19 monozygotic twin pairs stated that few or no other family members were affected by fainting spells, while in the other seven pairs of twins several close relatives also suffered syncope. The researchers interpreted this as an indication that probably several genes cause the susceptibility to fainting. "If it were a single gene," according to Samuel Berkovic, "one would expect the fainting rate to be similar among other relatives of the twins." However, the researchers did not discover that.

Fainting due to insufficient blood flow to the brain
Vasovagal syncope is neural, with a reflex causing the sudden expansion of blood vessels and a reduction in heart rate. The result is a sudden drop in blood pressure and insufficient blood flow to the brain. The victims lose consciousness in the short term 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 unpleasant and often dangerous. Possible causes of this sudden fainting may be, for example, acute stress, the sight of blood, fright, pain or even standing for a long time. (Fp)

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