A lawyer contacted Beatrice Golomb, a physician at the VA San Diego Healthcare Center, because he could no longer follow a normal conversation with his clients. A radiologist told Golomb that he found himself suddenly unable to distinguish left from right. A third person told her he had grown so forgetful that his doctor assumed he had Alzheimer’s.

All three had developed their memory problems after taking a cholesterol-lowering statin drug, and the symptoms improved after they stopped the medication.

The statin revolution began in 1987, when lovastatin was approved by the Food and Drug Administration (FDA). Since then, this class of drugs has transformed cardiac medicine, says Allen Taylor, chief of cardiology at MedStar Georgetown University Hospital. “Cardiovascular disease affects one in two people. This is the one drug that works.”

But these drugs are not without risks. Golomb has amassed thousands of reports at her website Statineffects.com, detailing adverse reactions from statins. She says that cognitive problems are the second-most-common side effect reported in her database, after muscle pain. In a 2009 report in the journal Pharmacotherapy, Golomb described 171 patients who’d reported cognitive problems after taking statins.

Eventually the FDA received enough such reports that last February it ordered drug companies to add a new warning label about possible memory problems.

Statin makers AstraZeneca, Bristol-Myers Squibb, Pfizer and Merck declined to comment for this article.

No one knows how common cognitive side effects are. Golomb says the data that she’s collected are all self-reported and voluntary. And the FDA’s MedWatch database is similarly built of mostly voluntary reports, though drugmakers are required to submit to the FDA adverse events that they know about. So without more systematic tracking, it’s impossible to measure how commonly these side effects occur. Many doctors believe the problem is fairly rare, posing little risk for the tens of millions of people using statins every day to keep their cholesterol levels in check.

“It’s not a very common side effect,” says Orli Etingin, an internist and professor in women’s health at Weill Cornell Medical College in New York. “But it’s definitely real. Typically, it’s a fairly high-functioning woman who is having difficulty remembering and multi-tasking.”

Taylor points out that clinical trials on statin use have never turned up memory problems and that researchers once held hopes that the drugs might actually prevent cognitive decline.

“I’m very skeptical of the link between statins and memory problems,” Taylor says. Most patients taking statins have a greater risk of developing cognitive decline from heart disease, which can impair blood flow to the brain.

If you’re taking a statin, what kind of problems should you look out for?

“Often it’s trouble with multi-tasking or word retrieval,” says physician Gayatri Devi, a neurologist in New York whose practice focuses on memory loss. “It’s short-term memory. It won’t make you forget your child’s name.” She warns against panicking. Don’t assume it’s your statin every time you can’t find your keys. Devi advises patients who worry that they may be having side effects to stop taking the drug for two weeks, under doctor supervision, to see if things improve.

For people without heart disease who take a statin as part of cholesterol-lowering strategy aimed at prevention, going off the statin for a month or two should not pose any risk, Etingin says.

If the symptoms stop after you go off the drug, the next step would be trying a different statin, Etingin says.

But don’t make any changes without consulting your doctor first, especially if you’ve already been diagnosed with heart disease, Taylor says.

If you suspect that a statin is impairing your memory, talk with your doctor about the options that make sense for you. “If your doctor says you’re crazy, look for another doctor,” Golomb says.