The new research results have been published in the scientific journal Cardiovascular Research. The researchers have analysed data from the UK Biobank containing information on approximately 400,000 Britons. 9,163 out of the 400,000 Britons had been in contact with the healthcare system due to fainting. In order to identify the genetic variants associated with fainting, the researchers systematically analysed millions of genetic variants in the participants’ genomes.
‘We have learned that a part of chromosome 2 increases the risk of fainting. This means that there is a genetic risk variant that predisposes to fainting. In addition, we are the first to show that fainting is genetically determined by linking an increased risk of fainting with an exact position in the genome,’ says Associate Professor Morten Salling Olesen from the Department of Biomedical Sciences, University of Copenhagen and the Laboratory for Molecular Cardiology, Rigshospitalet.
The researchers have also analysed data from a Danish cohort of 54,656 individuals called iPSYCH from Statens Serum Institut. The result confirmed their previous findings. Among the participants who had experienced fainting the researchers found the same genetic risk variant as in the British cohort. They discovered that women under the age of 35 faint approximately twice as often as men under the age of 35. The cause hereof is still unknown.
‘In the study we show that if you are a woman and you carry the risk variant on both chromosomes on chromosome pair number 2, you have an approximately three times increased risk of fainting compared with men not carrying the risk variant. Your gender and a single genetic variant in your genome reveal a substantial part of your risk of fainting,’ says Morten Salling Olesen.
The common belief is that fainting is caused by shortage of blood and oxygen to the brain, which results in short-term, total loss of consciousness. There are various types of syncope, the most frequent being vasovagal syncope. Here a reflex — e.g. triggered by the sight of blood — causes significant lowered blood pressure conditioned by a slow heart rate and a dilation of the blood vessels leading to reduced flow of blood to the brain and fainting.
Katra Hadji-Turdeghal, Laura Andreasen, Christian M Hagen, Gustav Ahlberg, Jonas Ghouse, Marie Bækvad-Hansen, Jonas Bybjerg-Grauholm, David M Hougaard, Paula Hedley, Stig Haunsø, Jesper H Svendsen, Jørgen K Kanters, Thomas A Jepps, Morten W Skov, Michael Christiansen, Morten S Olesen. Genome-wide association study identifies locus at chromosome 2q32.1 associated with syncope and collapse. Cardiovascular Research, 2019; DOI: 10.1093/cvr/cvz106