Is there a genetic component to heart disease?

Several studies conducted over the years have found that South Asians have a higher burden of Coronary Artery Disease (PCAD) compared to other ethnicities.

A 2004 INTERHEART study first found that the mean age of the first presentation of heart attack was 53 years, a full 10 years ahead of patients from Western Europe, China, Central and Eastern Europe.

Similarly, studies comparing the health of South Asian immigrants show that compared to local populations, they demonstrated a higher burden of CAD.

The INTERHEART study also indicated that South Asians who suffered a heart attack have low HDL-C (good cholesterol) levels, higher triglyceride levels, and a higher particle burden for LDL-C (bad cholesterol) levels.

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South Asians also have other risk factors, like dysfunctional HDL levels (where HDL particles lose their antioxidant and anti-inflammatory properties) and Lipoprotein (a) levels.

When asked about the roles of genes in Heart Disease, particularly among the Indian population, Dr Swathi Shetty, Assistant Professor at the Centre for Human Genetics, says the answer is not straightforward.

"If you have a history of heart disease in the family, that could indicate a higher genetic risk than the average population. But because there are so many variables causing heart disease, to pinpoint particular genes is difficult," Dr Swathi says.

CAD, like Cancer, is a multifactorial disease where genetics, environment and lifestyle play a major role. This is in stark contrast to single-gene disorders like Beta Thalassemia, Huntington’s disease or Cystic Fibrosis, where we know the gene associated with the disease.

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"Compared to cancer we are still way behind. We know much more about cancer genes. Cancer is basically the proliferation of cells. It is easier to look at those because we know there are genes which control the division. In Cardiovascular disease (CVD), there are many other factors involved, including the Nitric oxide in your vessels, coagulation factors, and many more," Dr Swathi says.

For instance, in 2011, 58 genomic regions associated with CAD were discovered, but most of the heritability cannot be explained.

"They have done studies among people with CVDs and looked for areas of DNA that they have in common. And we have found regions that are not even an expressed gene. That is another layer of difficulty. It [gene] doesn't code for a protein. Is it really increasing the risk? For these, we need huge numbers of patients to try and correlate," Dr Swathi adds.

Another 2018 paper studying Premature Coronary Heart Disease burden in South Asians identified six variants of the CX3CR1 gene which were unique to South Asians and "not found in large (mostly European) cohorts".

But the study concluded that findings "do not allow definite conclusions, especially with regard to how these could impact therapy."

“While CAD does seem to have a genetic component involved, we also know that lifestyle factors like smoking, exercise, stress management etc also impact development of the disorder, which is something that people can still control and moderate,” Dr Swathi adds.

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