DNA tests: surprise finding

NEW YORK: If you learned your DNA made you more susceptible to getting a disease, wouldn’t you work to stay healthy?

You’d quit smoking, eat better, ramp up your exercise, or do whatever else it took to improve your odds of avoiding maladies like obesity, diabetes, heart disease or cancer, right?

The scientific evidence says: don’t bet on it.

DNA testing for disease risk has recently expanded in the US. The company 23andMe recently started selling the nation’s first approved direct-to-consumer DNA tests that evaluate the buyer’s genetic risk for certain diseases or conditions.

The field also gained a new entrant in July, when a company called Helix launched an online marketplace for DNA tests, including some for genetic health risk.

Helix decodes a consumer’s DNA and passes the results along to another company for analysis.

A request for the currently available health tests must be approved by a physician’s group that reviews the customer’s medical history.

DNA tests for diseases typically assess genetic predisposition to getting sick. They don’t provide absolute predictions about whether or not a disease will strike. Genetic risk is only part of a person’s overall risk, which includes influence from other things like a person’s lifestyle.

While some diseases are caused by a single malfunctioning gene, more common illnesses are influenced by multiple genes and often each gene nudges a person’s risk only slightly.

Last year, researchers published an analysis that combined 18 studies of people who got doctor-ordered DNA test results about disease risks.

The result? Getting the DNA information produced no significant effect on diet, physical activity, drinking alcohol, quitting smoking, sun protection or attendance at disease-screening programmes.

That fits with other results showing that, on balance, getting the information “has little if any impact on changing routine or habitual behaviours”, said psychologist Theresa Marteau of Britain’s Cambridge University, a study author.

Dr Robert Green of Brigham and Women’s Hospital in Boston said people sought such results for a number of reasons, including simple curiosity, so the value of DNA testing should not be judged simply by whether it changes health behaviour.

“I think people have a right to this information,” he said. – AP