Researchers carried out brain scans on 1,400 women aged 71 to 89 who had participated in the Women’s Health Initiative, a major American study.
They found women who had been on HRT had smaller brain volumes in two key areas than those given a placebo. Brain volume was 2.37cc lower in the frontal lobe and 0.10cc lower in the hippocampus.
Both areas of the brain are involved in thinking and memory skills, and hippocampus shrinkage is a known risk factor for dementia.
The study leader, Dr Susan Resnick, of the US National Institute on Ageing in Baltimore, Maryland, said: “These effects were most apparent in women who may already have had some memory problems before they started taking hormones.”
She added: “This suggests that oestrogen may adversely affect thinking skills among women whose brains may already be beginning a neurodegenerative disease process.”
It had been thought “silent strokes” might account for some memory-loss in HRT users.
The Women’s Health Initiative trial was a landmark American study which highlighted a link between long-term HRT and increased stroke risk.
