Our genome — the blueprint for what makes us who we are — can provide valuable clues about our health and potentially help us predict our risk for various diseases. But a new study shows that knowledge of our DNA isn’t actually as revealing as doctors hoped.
In a report published in the American Journal of Human Genetics, scientists at the Harvard School of Public Health found that incorporating genetic information did not improve doctors’ ability to predict disease risk above and beyond standard risk factors, including things like family history, lifestyle and behavior. So, having detailed genetic information didn’t change doctors’ prevention or treatment plans.
“For most people, your doctor’s advice before seeing your genetic test for a particular disease will be exactly the same as after seeing your tests,” Peter Kraft, a co-author of the paper and an epidemiologist at the Harvard School of Public Health, said in a statement.
The researchers looked at risk factors — both genetic and environmental — for three common, chronic diseases, breast cancer, Type 2 diabetes and rheumatoid arthritis. All conditions are known to be influenced by some genetic and some lifestyle factors. The researchers wanted to determine whether adding information about the interplay of these factors would improve the sensitivity of disease risk prediction.
For breast cancer, the scientists created a simulation that included 15 common genetic variants associated with increased risk of the disease, along with environmental factors, such as a woman’s age at first period, age when she gave birth to her first child and the number of close relatives affected by breast cancer. For Type 2 diabetes, researchers included 31 genetic variants, as well as lifestyle factors like obesity, physical activity, smoking status and family history of diabetes. Finally, for rheumatoid arthritis, they considered 31 genetic variants and two major lifestyle risk factors — smoking and breast-feeding.
The researchers analyzed whether interactions among the genes, or interactions between genes and environmental factors, significantly changed the risk profile for any of these diseases. The disease models generated a variety of statistical combinations of genetic and environmental factors, but none produced any marked improvement in predicting disease risk over the lifestyle factors alone.
So, while genome sequencing has become a popular buzzword in medicine, the researchers conclude that given our current limited ability to interpret the genome or understand the complex interplay between genes and environment, getting genetic tests or whole-genome sequencing may not be as helpful as it could be when it comes to informing our health decisions. Even with the current list of 15 genetic variants associated with breast cancer, for example, scientists can’t tell which variants are driving disease or are necessary to cause it, and which are merely along for the ride.
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That type of knowledge may emerge in coming decades, however, with better understanding of which genes contribute to diseases like cancer, diabetes or immune conditions, and how they work. As the authors write: “…[A]n understanding of the interplay between genes and the environment can provide insights into disease etiology; this understanding, in turn, can lead to improved treatment and prevention strategies.”