Heredity and environmental factors influence your susceptibility to various diseases. (Image credit: Hiroshi Watanabe via Getty Images)
While waiting to see my doctor, I was stunned when she said, “Genetics really don’t matter that much for chronic disease.” Then she added, “How we live, what we eat, and how much exercise we do determines our likelihood of developing heart disease.”
As a researcher in the field of disease genetics, I can’t agree more — lifestyle factors do play a significant role in who gets sick and who doesn’t. However, that’s not the whole story. Since mapping the human genome in 2003, scientists have discovered that genetics also plays a significant role in disease risk.
Studies that focus on the heritability of diseases—that is, the extent to which genetic differences explain differences in disease risk—typically attribute a significant proportion of the variation in diseases to genetic factors. Genome-wide mutations appear to influence diseases such as type 2 diabetes, which is about 17% heritable, and schizophrenia, which is about 80% heritable. Unlike diseases such as Tay-Sachs or cystic fibrosis, where mutations in a single gene cause the disease, chronic diseases tend to be polygenic, meaning they are affected by many mutations in different genes across the genome.
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