myDNAhealth comments on polygenetic risk scoring test for common diseases
myDNAhealth provides some perspective on a recent study conducted by scientists at Harvard and MIT about genetic testing for chronic conditions. The study appeared in national media earlier in the week with a story in The Times today entitled “Genes put millions at triple risk of heart attack”.
The scientists behind the study are hoping that soon everyone could be given a “heart attack score” from birth that would tell them their chances of suffering coronary heart disease on the basis of genetics alone.
Coronary heart disease is a leading cause of death worldwide and the study reports about five million Britons have at least triple the normal risk of suffering a heart attack despite lacking warning symptoms. The study also identified millions of other people whose genetics put them at a threefold or more risk of bowel disease, atrial fibrillation, breast cancer and type 2 diabetes. Most will have no reason to suspect that they are likely to suffer from the diseases.
Genome-wide polygenic analysis
The study refers to polygenetic analysis, so we will briefly explain what this means. Many characteristics observed in humans (phenotypes) are a result of the inheritance of multiple genes. Common examples that we see every day are variations in our hair colour – many genes are expressed in different quantities to produce the resulting shade that we see. This is known as polygenic inheritance.
Many adult onset diseases such as cardiovascular diseases, type 2 diabetes, cancers and inflammatory diseases are also caused by the contributing action of many genes.
A novel technological development in genetic testing
Khera and colleagues have developed an interesting method to test for polygenic mutations. The authors analysed 400,000 participants of British descent and developed an algorithm to determine an individual’s risk for diseases based on the amount of genetic variations (also called risk alleles) that the participants carried in their DNA (Khera et al., 2018). The average age of the participants of the Bayer AG funded study was 57 and 55% of the participants were female.
The authors claim the technology can be used to test newborns as the newly developed polygenic analysis does not take environmental and lifestyle risk factors into account.
This new technology is very exciting as it has the potential to be used as a diagnostic tool for many preventable diseases and early mortalities. However, of course, there are ethical implications about whether finding out your child’s risk factors shortly after birth would benefit or harm their life.
There is also the Global Burden of Disease (GBD) study to take into consideration. GBD reported risk factors contributing preventable mortality and it appears it’s our lifestyle choices such as diet and exercise that determines 40 percent; social and environmental factors, such as where a person lives and their education, accounts for 20 percent; genetics contributes 30 percent and medical care a mere 10 percent.
References
The Times “Genes put millions at triple risk of heart attack” accessed 14/08/2018 https://www.thetimes.co.uk/article/genes-put-millions-at-triple-risk-of-heart-attack-nw77wm28r
Khera, A. V., Chaffin, M., Aragam, K. G., Haas, M. E., Roselli, C., Choi, S. H., … Kathiresan, S. (2018). Genome-wide polygenic scores for common diseases identify individuals with risk equivalent to monogenic mutations. Nature Genetics, 1. https://doi.org/10.1038/s41588-018-0183-z
Global Burden of Disease (GBD) study: http://www.healthdata.org/gbd
