People who take statins, the popular medications that lower cholesterol, are less likely to develop gallstones that lead to having their gallbladder removed.

Researchers reporting in this week's issue of JAMA, Journal of the American Medical Association found that statin medications prescribed for at least a year appear to reduce the risk for gallstone surgery, called cholecystectomy.

The reason may have something to do with the way statins work.

Most gallstones are made from cholesterol deposits that occur in bile, a fluid that helps break down fats in our intestines. While all bile naturally contains some cholesterol, if there is too much, gallstones can form. That can lead to severe cramping pain and intestinal problems; in the most serious cases, the gallbladder has to be removed.

Since statins decrease liver cholesterol biosynthesis, it's thought they also lower the risk of gallstones by reducing cholesterol concentrations in the bile.

While that might sound logical, the authors led by Dr. Michael Bodmer, of University Hospital in Basel, Switzerland, note that data on the action of statins on gallstones in humans has been scarce.

Bodner led a team that conducted a large, long-term study on the link between statin use and the risk of developing severe gallstone disease that resulted in gallbladder removal.

They reviewed data on more than 27,000 U.K. patients who underwent gallbladder surgery between 1994 and 2008. They then compared them with more than 100,000 control patients. Of these, 2,396 patients and 8,868 controls had a history of statin use.

The researchers found that those on statins were one fifth less likely to develop gallbladder disease. However, they didn't see the effect on those who took the medications for less the year. The surgery risk was reduced only when patients had completed five prescriptions of treatment, reflecting about one to 1.5 years of treatment.

Patients who had filled fewer than five prescriptions saw zero benefit, those who had filled five to 19 prescriptions had a 15 per cent reduced risk, while those who had filled 20 or more had a 36 per cent reduced risk.

And the higher the dose of statin, the lower the risk of gallstone surgery.

"This large observational study provides evidence that patients with long-term statin use have a reduced risk of gallstone disease followed by cholecystectomy compared with patients without statin use," the authors write.

The researchers found it didn't matter the age of the patients or their gender or even the kind of stain they took; the findings still held.

Even adjusting for important risk factors for gallstone disease, including obesity, high-fat diets and estrogen replacement therapy didn't significantly alter the results.

"Our findings may be of clinical relevance given that gallstone disease represents a major burden for health care systems," the researchers conclude.