Preliminary results from a study on the safety of the hormone therapy medication Prempro indicate the drug may have a negative impact on women's memories and their ability to comprehend ideas and surrounding events. Expected to be published in a major medical journal next month, the study is a separate arm of the Women's Health Initiative, a government report published last July that linked Prempro, made by Wyeth, to breast cancer, stroke and heart disease.

The latest analysis reportedly found negative cognitive effects in a small percentage of women aged 65 and older. One industry analyst said because the drug may cause clotting that leads to strokes, it may also lead to brain clots that contribute to dementia among the elderly.