Genes and Your Health

If your father had a heart attack in his 50s, you may worry, “Will that happen to me?”

If you have rheumatoid arthritis (RA), you may wonder, “Will I pass this on to my child?”

Such concerns “come up a lot in families. People will say they have a brother, a cousin, a parent who has one of many conditions,” says Bryce Mendelsohn, MD, PhD, who specializes in medical genetics at the University of California, San Francisco. But he can usually respond with good news: Just because someone in your family has a disease doesn’t mean you’ll get the same one -- or pass it on to your kids.

Genes are made up of DNA, the molecule that holds the blueprint for how you grow, develop, and survive. They have a lot to do with your health. And so do your lifestyle and things in the world around you.

How Lifestyle Impacts Health

Sometimes scientists refer to “environmental factors” when they talk about your health. This phrase might mean clean air and water. It could refer to the sun’s cancer-causing rays. And it can also include lifestyle choices, like whether you smoke or get enough exercise. Here are a few examples:

• Stress, especially ongoing stress from work or family, may play a part in heart disease, high blood pressure, diabetes, depression, and other health issues. That’s why it’s so important to find healthy ways to handle it, whether you take a walk, get talk therapy, or cut back on alcohol.
• Cigarette smoking can cause more than 10 types of cancer, including those of the lung, kidney, liver, and colon. It’s also linked to heart disease, stroke, and other serious conditions.
• Obesity is tied to several health problems, like sleep apnea, type 2 diabetes, stroke, cancers, and osteoarthritis.

Anyone who’s tried to lose weight or quit smoking knows how hard it can be to make healthy choices consistently over time. You do have some control, but you can’t change your genes.

The Role of Genes

They determine your hair color, your eye color, and how tall you are. In some cases, they also control whether you’ll get a disease.

Mendelsohn points to phenylketonuria, a disorder that causes blood levels of a substance called phenylalanine to rise. Treatment can make it a little bit better, but you’ll still have the disease. Other diseases caused by changes to your genes -- the doctor will call the changes "mutations" -- include cystic fibrosis, sickle cell disease, and Huntington’s disease.

On the other hand, having a gene with a strong link to a disease doesn’t always mean you’ll get sick. For example, Alzheimer’s disease appears to have genetic ties. But people who have the gene don’t always get it, and some people who get it don’t have the gene.

When It’s More Than Genes

Rheumatoid arthritis is a good example of a disease that falls in the middle of the spectrum. Sometimes there’s a genetic link: If you have a close relative with it, you’re more likely to get it. But environment and lifestyle choices may also play a role. Smoking can raise your odds. Other causes include changes in sex hormones and certain infections.

Then there are conditions in which genes play some role, but lifestyle choices make more of a difference when it comes to whether or not you’ll get it. Type 2 diabetes is a prime example. Certain genes and excess weight both can boost the chance that you'll have it. But “a person of a normal weight, even if they have the highest-risk genetics, probably won’t get diabetes. The person who’s overweight, even if they have the lowest-risk genetics, might still get diabetes,” Mendelsohn says.

How Precision Medicine Helps

The more doctors know about the role of genes in our health, the better they can diagnose and treat disease. Testing the genes of newborns that have mystery illnesses turns up a genetic link about 25% of the time, says Jeanette McCarthy, PhD, an adjunct associate professor at Duke University Medical Center's Institute for Genome Sciences and Policy. “There’s value not only from finding a cause and ending the mystery, but then in some cases being able to treat them.”

That’s one of the ways precision medicine, which is still a new field, is making a positive impact. Another is how it helps doctors prescribe the right drugs at the right doses for the right patients. McCarthy offers some examples:

• The epilepsy drug carbamazepine can have rare but severe side effects. A genetic test can let doctors know if you’re more likely to have the side effects and thus shouldn’t take it.
• Several drugs are designed to target certain genetic abnormalities, including ivacaftor (Kalydeco), a drug approved for people with certain mutations in their cystic fibrosis gene.

Researchers are also looking for ways to improve health habits in certain groups of people who are more likely to get diseases from poor health choices. For example, smoking is a tough habit for anyone to break. But now the low- income African-American community, which has been a target of tobacco ads and promotions for decades, is getting specially tailored programs and materials to help smokers kick the habit.

Efforts are also underway to prevent more cases of type 2 diabetes. One example: Researchers are working on a tool to find people most likely to get the disease. It uses blood sugar and other things, so there’s no need for genetic tests. It would also help doctors decide who might benefit from a pre-diabetes drug and lifestyle changes alone.

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