Why more women than men suffer from Alzheimer’s

WASHINGTON — Nearly two-thirds of Americans with Alzheimer’s disease are women, and now some scientists question the long-held assumption that it’s because they tend to live longer than men.

A recent Alzheimer’s Association report estimates that at age 65, women have about a one-in-six chance of developing Alzheimer’s during the rest of their lives, compared with a one-in-11 chance for men.

“It is true that age is the greatest risk factor for developing Alzheimer’s disease,” said University of Southern California professor Roberta Diaz Brinton, who presented data on gender differences at a meeting of the National Institutes of Health this year.

However, she added that on average, “women live four or five years longer than men, and we know that Alzheimer’s is a disease that starts 20 years before the diagnosis”.

Prof Brinton researches if menopause can be a tipping point that leaves certain women vulnerable.

There’s some evidence that once Alzheimer’s is diagnosed, women may worsen faster; scans show more rapid shrinkage of certain brain areas.

Stanford University researchers analysed records of more than 8,000 people for a form of a gene named ApoE-4, long known to increase Alzheimer’s risk.

Women who carry a copy of that gene variant were about twice as likely to eventually develop Alzheimer’s as women without the gene, while men’s risk was only slightly increased, said Stanford University’s Dr Michael Greicius.

It’s not clear why. It may be in how the gene interacts with oestrogen, Prof Brinton said.

What drives the difference in Alzheimer’s cases isn’t clear, said Professor Susan Resnick of the National Institutes of Health, pointing to conflicting research.

“We have a tough time understanding whether or not women really are more affected by the disease, or it’s just that they live longer,” Prof Resnick said.

Data from the long-running Framingham Heart Study, which has been studying heart-disease risk since 1948, suggests that because more men die from heart disease in middle age, those who survive past age 65 may have healthier hearts that, in turn, provide some brain protection. Many of the same factors — obesity, high cholesterol, diabetes — that damage arteries are also Alzheimer’s risks.

What about hormones? Years ago, a major study found that oestrogen therapy after age 65 might increase risk of dementia, although later research showed hormone replacement around the onset of menopause wasn’t a problem.

Prof Brinton studies how menopause changes the brain. Oestrogen helps regulate the brain’s metabolism and it must switch to a less efficient backup method as oestrogen plummets, she said.

“It’s like the brain is a little bit diabetic,” said Prof Brinton, who is studying whether that may relate to menopausal symptoms in women who later experience cognitive problems. AP