People taking higher strength statins to lower their cholesterol levels could be increasing their risk of being hospitalized for kidney problems, Canadian researchers have found.

Statins are among the most widely used prescription drugs, particularly for those with cardiovascular disease. Doctors also prescribe statins to people with high cholesterol without a history of heart disease. For these patients there's debate over whether the possible side-effects outweigh the risks.

Some patients may be exposed to unnecessary risk of kidney damage from cholesterol-lowering statins for small gains in cardiovascular health. (Scott Olson/Getty)

When investigators analyzed the health records of 2 million people in Canada, the U.S. and the UK with an average age of 68, they found high potency statin users were more likely to be hospitalized for acute kidney injury compared with those prescribed low potency statins.

In the study, kidney injury was defined in terms of short-term impact on kidney function.

The high potency statins in the study were:

• Rosuvastatin (e.g. Crestor) at doses of 10mg or higher.
• Atorvastatin (e.g. Lipitor) at doses of 20mg or higher.
• Simvastatin (e.g., Zocor) at doses of 40mg or more.

Researchers considered all other statins low potency.

"We estimate that 1,700 patients with non-chronic kidney disease need to be treated with a high potency statin instead of a low potency statin for 120 days to cause one additional hospitalization for acute kidney injury," Colin Dormuth, assistant professor of anesthesiology, pharmacology and therapeutics at the University of British Columbia, and his co-authors concluded in this week's issue of the British Medical Journal.

In absolute terms the risk is low, Dormuth said.

But the researchers are still cautioning patients and doctors. "Our findings put into question the common approach of using higher doses to push cholesterol levels lower and lower," Dormuth said in a release. "In some cases, patients may be exposed to unnecessary risk of kidney damage for small gains in cardiovascular health."

Rapidly losing kidney function can have long-lasting consequences, such as needing dialysis.

The research was done by researchers at the Canadian Network for Observational Drug Effect Studies, or CNODES. It included data on patients in British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Quebec and Nova Scotia.

A journal editorial accompanying the study titled "Statins in acute kidney injury: friend or foe?" said since some studies also suggest statins could potentially prevent acute kidney injury after major elective surgery, more research is needed to understand how statins could cause the damage.

"Clinicians should use low potency statins whenever possible to provide cardiovascular benefits without the increased risk of acute kidney injury," Robert Fassett and Jeff Coombes of University of Queensland in Australia wrote in the editorial.

"Despite extensive experience with the use of statins over many years, optimization of doses to derive benefit but minimize risk is still evolving."

CNODES is funded by Health Canada and the Canadian Institutes of Health Research.