The relationship between heart disease and high cholesterol levels has been known for a long time. Although poor diet and lack of exercise are common causes of high cholesterol, up to 50% of high cholesterol cases are estimated to be inherited. Unfortunately, there is no way to screen for individuals at high risk of high cholesterol and/or heart disease. In fact, the mutations in genes discovered so far account for only a small amount of high cholesterol levels noted.
Previous studies have linked certain genes and single nucleotide polymorphisms, or SNPs, to causing high cholesterol levels. DNA consists of chains of nucleotides. SNPs are variations in single nucleotides within a DNA sequence and occur with some frequency across different populations (like Europeans or Asians). In order for this variation to be considered a SNP, it must occur in at least 1% of individuals. SNPs don’t necessarily cause disease; however, they can influence the way you respond to diseases, microorganisms, drugs, and the way you metabolize certain substances, including cholesterol. Researchers at Massachusetts General Hospital in Boston, MA wanted to identify the relationship between these SNPs and the incidence of high cholesterol and heart disease, and see whether or not they could predict the risk of heart disease in individuals having problematic SNPs.
The researchers looked at roughly 5,400 Swedish individuals for this study over a 10-year period. For this study, they examined HDL and LDL cholesterol levels, as well as the presence of SNPs on nine genes previously known to be linked to high cholesterol levels. They found that having more of the unfavorable SNPs corresponded to higher LDL levels and lower HDL levels.
Additionally, those individuals who had a higher number of SNPs also had a higher risk of having a heart attack, stroke, or cardiac death. Of the participants in this study, 238 individuals (or about 5% of people tested) had a heart attack, stroke or cardiac death. While testing for these SNPs was not any better than looking for other risk factors for heart disease (such as high cholesterol), the researchers felt that adding this test could help better distinguish between those individuals who are at a higher risk of having heart disease.
It will be a long time before you make an appointment at your healthcare provider’s office for a genetic screening for heart disease, but this does add to our knowledge that genes play a bigger role in heart disease and high cholesterol levels than we once thought. However, SNPs can vary between ethnic groups, so the SNPs seen in this population tested may not reflect the SNPs you would see in the United States.
Source:
Kathiresan S, Melander O, Amevski D, et al. Polymorphisms associated with cholesterol and risk of cardiovascular events. NEJM 2008. 358:1240-9.
