As genetic sequencing has become more affordable and commonplace, scientists have been trying to decipher how genes relate to disease. Past studies have indicated that only 0.02 percent of the population is born with a genetic condition. But according to a study from researchers at the National Institutes of Health, 10 percent of the population may have mutations that make them more susceptible to disease, resulting in genetic conditions in as much as 3 percent of the population. By understanding which mutations cause disease, or why they affect some people and not others, researchers could help prevent the onset of disease for an even larger fraction of the population.
In the study, published last week in the American Journal of Human Genetics, researchers recruited nearly 1,000 volunteers who seemed to be healthy based on blood and heart tests as well as self-reported symptoms. They also asked about their family history and sequenced their genomes. Since all the volunteers were between 45 and 65 years of age, signs of genetic disease would have been clear.
The study found that about 100—more than 10 percent—of the participants had a genetic variant that would make them more likely to have a disease. More often than not, the disease associated with the mutation ran in patient's family, but that individual often didn't notice the trend. Thirty-four of the participants had unknowingly been living with the disease in question—one man, for example, had a mutation associated with deafness and, though he said he didn't have any hearing problems, a clinical test showed that he had moderate to severe hearing loss.
Three percent of the volunteers had the mutations for diseases, but didn't have the disease itself. One patient had the mutation for Coffin-Siris Syndrome, which can limit a person's intellectual capacity, but an IQ test showed that he was more intelligent than the average person.
The researchers were surprised by their results. They hope that future studies will do more to uncover why only some people with mutations present the associated disease and make strides in preventative medicine.