From the article:
Called the Estrogen in the Prevention of Atherosclerosis Trial (EPAT) the study monitored how much artery walls thickened over two years in 222 healthy postmenopausal women who took unopposed estrogen or a placebo.
Women on estrogen therapy saw their atherosclerosis rate decrease by .0017 millimeters (mm) per year over two years, while artery wall thickness increased by .0036 mm per year over two years in women who took a placebo.
As a guideline, Hodis says, an increase of .033 mm per year translates to a two-to-three-fold increase in risk of events such as heart attacks, and a starting thickness of .8 mm or greater also puts an individual at high risk.
[…]
Also, EPAT investigators could compare women who used cholesterol-lowering drugs against women who did not take such medication. Besides taking estrogen or a placebo, all women who started the trial with levels of 160 or higher of low-density lipoprotein (often called LDL or “bad” cholesterol) were put on a cholesterol-lowering medication.
Among the group of women who took no cholesterol-lowering medications in EPAT, those on estrogen therapy had .0147 mm per year slower atherosclerosis progression than those who took a placebo.
Interestingly, women who received both estrogen and cholesterol-lowering drugs had about the same decrease in atherosclerosis progression as women who took cholesterol-lowering drugs alone.
Researchers do not know why the combination of estrogen and cholesterol-lowering drugs does not result in even further atherosclerosis improvement. “But the effects of lipid-lowering drugs are quite powerful,” Hodis says. “You’re probably not seeing any effect above that.”