Muscle problems caused by statins: Can a genetic test reveal your risk?

In the United States, more than 40% of people ages 60 and older take a cholesterol-lowering statin to reduce their risk of a heart attack. But up to half of people who are prescribed these drugs quit taking them because they experience what they believe to be statin-related side effects — most often muscle pain. Others avoid statins altogether because of that worry. That's why many people might be curious about a mail-order genetic test called StatinSmart, which bills itself as the first test to identify a person's risk of experiencing muscle pain from a statin.

But here's the rub: muscle problems can range from mild to serious, and the terms experts use to describe them can be confusing. The StatinSmart website says 29% of people who take a statin develop "statin-induced myopathy," which they define as muscle aches, pains, weakness, or cramps.

"That seems like a gross overestimate of the symptoms that are actually caused by statins," says Dr. Kiran Musunuru, assistant professor of medicine at Harvard Medical School. He and other doctors concur that some people who take statins develop debilitating aches and pains that then go away once they stop taking the drug. But those people represent just a small percentage of statin users. Among the 60-plus crowd, who are the most likely to be prescribed a statin, muscle-related symptoms are fairly common and have many causes, including strenuous exercise, infections, or other health problems.

Serious but rare

In the study used to validate StatinSmart's genetic test, the researchers defined myopathy as symptoms of myalgia (muscle pain) in addition to a creatine kinase (CK) level more than 10 times higher than normal. CK is an enzyme in the blood that rises in response to muscle damage. This type of myopathy is very serious but quite rare, affecting about one in 1,000 people who take statins, says Dr. Musunuru.

What exactly does StatinSmart measure? Using genetic material from a small sample of your saliva, the test analyzes a gene called SLCO1B1. Variants in this gene, which affects a protein that helps shuttle statins into the liver, are linked to the rare form of statin-induced myopathy.

About 75% of people have two normal versions of the gene and thus aren't at risk for severe myopathy. About 23% of people have one copy of the gene, which means they're about four to five times more likely to develop statin-induced myopathy than the average person. And 2% of people have two copies of the gene. Those people are about 17 times more likely to develop statin-induced myopathy. However, even if you're in that 2% minority, your chances of developing statin-induced myopathy are still very low: 17 in 1,000.

A family history of myopathy?

So should anyone consider taking this test, which costs $99? "If we had an alternative drug that was proven to lower heart attack risk just as effectively and inexpensively as a statin, then yes, it might make sense," says Dr. Musunuru. People who had the gene variant could then take the alternative drug.

For most people, the very low risk of serious myopathy is outweighed by the benefit of a statin. But if one of your close relatives (a parent or sibling) had statin-induced myopathy, then the StatinSmart test may be a reasonable idea, says Dr. Musunuru. You should do so in collaboration with your physician (as the company recommends), who can tailor your statin therapy according to your results.

If you develop muscle pain or weakness while taking a statin, your doctor may advise you to stop taking it, wait a month or two, then try taking it again. If the muscle trouble returns, your doctor can change the dose or type of statin or take you off the drug. Of course, if you have any persistent, unexplained muscle pain, ask your doctor about CK testing whether or not you're taking a statin.