Women with high levels of estrogen have more than double the risk of dementia, researchers found in the latest study to cast doubt on the health benefits of the female sex hormone.
The connection between estrogen levels and dementia was even greater in women who suffered from diabetes, according to the study, published today in the medical journal Neurology. For diabetic women with high estrogen, the risk of dementia may increase 14-fold, the French researchers found.
Estrogen was long viewed as beneficial for women’s health, with an ability to subdue post-menopausal symptoms and have positive effects on the heart and brain. Lately, scientists have tried to understand the role that the hormone plays in cognitive function, and some doctors are advising against taking it as a supplement amid links to cancer and blood clots.
“This study, together with other current data, challenge this dogma” that the hormone is beneficial, Pierre-Yves Scarabin, one of the authors and team director of cardiovascular disorders and hormones at the French National Institute of Health and Medical Research in Villejuif, said in an e-mail. “Mechanisms underlying this association remain to be clarified.”
An earlier study in women ages 65 and older linked hormone treatments to cognitive decline, whereas another study published last year found that women ages 50 to 55 years old didn’t suffer harm to their brain function.
The French study didn’t focus on patients who were taking hormonal therapy. The scientists measured the level of estrogen occurring naturally in the blood of women ages 65 years and older without dementia in Bordeaux, Dijon and Montpellier, France. Four years later they were followed up and 543 women who had no dementia were compared with 132 who did. The researchers also looked at risk factors including high-blood pressure, blood clotting and other indicators of heart health.
About 382 million people worldwide have diabetes, and that number may rise to an estimated 592 million by 2035, according to the International Diabetes Federation. Alzheimer’s Disease International estimates that 44 million people worldwide suffer from dementia, a number expected to grow to 76 million in 2030 and 135 million by 2050, according to data from the group of Alzheimer’s associations.
The researchers called for further study of the topic “given the biological plausibility of this interaction and the expected increase in the number of elderly people with diabetes and/or dementia.”
Other clinical trials have identified health risks associated with some hormone-replacement therapies. The study didn’t address questions about specific drugs such as Pfizer Inc.’s Premarin, which is prescribed to some women who suffer symptoms such as hot flashes and night sweats after menopause.
The French study was funded by the French National Institute, the Victor-Bordeaux 11 University, and other groups, as well as drugmaker Sanofi.