Statin drugs have contributed to the drop in average cholesterol levels among older Americans since the 1960s, according to a new study.

Researchers from the Centers for Disease Control and Prevention reported that average total cholesterol levels for men and women ages 20 to 74 dropped from 222 milligrams per deciliter of blood to 203 between 1960 and 2002. The drop is mostly due to a decline among those 50 and older.

Among Americans ages 60 to 74, average levels fell 12% among men and 15% among women. Below 200 is considered desirable with regard to average risk for heart disease.

Statins, which include Pfizer Inc.’s Lipitor, Bristol-Myers Squibb Co.’s Pravachol and Merck and Co. Inc.’s Zocor, are commonly prescribed to lower dangerously high levels of low-density cholesterol in the blood, the cholesterol known to clog and damage arteries and lead to heart disease.

The study was published in the Journal of the American Medical Association.