LITTLE ROCK, Ark. (AP) -- Cholesterol lowering drugs known as statins can increase the life expectancy of elderly patients by an average of two years, a new study by a doctor at the University of Arkansas for Medical Sciences claims.

The study by Dr. J.L. Mehta tracked nearly 1.5 million patients in the U.S. Department of Veterans Affairs' South Central Healthcare Network. Doctors prescribed statins to about 350,000 patients, almost half older than 70. Another 1.2 million patients did not receive the drugs.

The study, which began in 2004, found those at greater risk of death received the greatest benefit of being on the drugs. Doctors typically prescribe statins to elderly patients with a history of coronary artery disease, hypertension, diabetes and smoking.

"We were surprised to find that statin users actually lived an average two years longer despite the patients having more health risk factors and being older than non-statin users," Mehta said in a press release.

"We did not expect that statin therapy would have such a profound impact on patients' lives."

Statins reduce the amount of cholesterol produced by the liver. Cholesterol can form plaque within arteries, which reduces blood flow and can cause heart attacks and strokes. By lowering the amount of cholesterol in the blood, statins can slow plaque buildup and can help reduce the amount of existing plaque.