Two-thirds of people living with Alzheimer’s in the United States are women. Researchers are trying to determine the reasons.

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Researchers say determining why women are at higher risk of Alzheimer’s could lead to better treatments and prevention. Getty Images

Two-thirds of people in the United States living with Alzheimer’s are women, and researchers say they have found the progression of the disease might be different for women and men.

The research, published earlier this week, adds to a growing body of evidence that suggests women might be at an increased risk for certain physiological changes associated with the disease.

In undertaking their work, the researchers focused on a marker of Alzheimer’s disease known as tau protein, a naturally occurring substance found in the brain.

“We know that tau builds up over time in all people in certain areas of the brain. Once abnormal levels of amyloid build up in the brain in individuals at risk of Alzheimer’s, however, we see that tau starts to appear in more and more areas of the brain associated with memory,” Rachel Buckley, PhD, author of the study and research fellow in neurology at Massachusetts General Hospital, told Healthline.

“In healthy, older adults who already show higher levels of amyloid, women show subtle, but measurable, differences in the amount of tau that they have in their brain comparative to men. This suggests to us that, by the time amyloid has taken hold in the brain, women may show an accelerated pattern of disease relative to men,” she explained.

Previous studies have shown higher levels of diagnoses for Alzheimer’s in women as well as a faster cognitive decline in women compared with men.

Of the 5.5 million Americans age 65 and older living with Alzheimer’s, 3.4 million of them are women.

A woman in her 60s is twice as likely to develop Alzheimer’s disease during the remainder of her life than breast cancer. In Americans aged 71 or older, 16 percent of women have Alzheimer’s or dementia compared with 11 percent of men.

“Women are at the epicenter of Alzheimer’s — as people living with the disease and as care partners. Two-thirds of people living with Alzheimer’s are women, as are two-thirds of the people caring for them. We need to know more about why Alzheimer’s impacts more women than men,” Keith Fargo, PhD, director of scientific programs and outreach at the Alzheimer’s Association, told Healthline.

“The prevailing view has been that this discrepancy is due to women living longer than men, on average, and older age is the greatest risk factor for Alzheimer’s. Researchers are now investigating whether the risk of Alzheimer’s could actually be higher for women at any given age due to biology or genetics, or differences in life experiences,” Fargo said.

Dr. Michael Greicius is an associate professor of neurology at Stanford University in California. He says the reason Alzheimer’s appears to impact women more than men is complex.

“Even when correcting for increased longevity in women, it seems to be true that women are more susceptible to developing Alzheimer’s,” he told Healthline. “One confounding factor is that in previous generations, those that are now contributing to the rising numbers of Alzheimer’s cases, women tended to be less well-educated than men, and education provides some protection against the diagnosis of Alzheimer’s. Another important factor is that the APOE4 gene, the strongest genetic risk for late-onset Alzheimer’s, also increases the risk of heart disease. It is possible that the heart disease risk of APOE4 takes a bigger toll in men than in women such that some APOE4-carrying men may die of heart disease before they develop Alzheimer’s.”

According to the Centers for Disease Control and Prevention (CDC), the number of people living with Alzheimer’s disease in the United States is expected to triple to 14 million by 2060.

The disease is the only top 10 leading cause of death in the United States that cannot be slowed, prevented, or cured.

Alzheimer’s is the sixth leading cause of death among adults in the United States, and the fifth leading cause of death among adults over 65.

In 2010, the estimated cost of treating Alzheimer’s was between $159 billion and $215 billion. By 2040, it’s expected these costs will increase to between $379 billion and $500 billion every year.

Experts say that although research surrounding the biological differences of the disease between men and women is still being undertaken, understanding such differences could pave the way for better treatments and prevention options.

“Delineation of the basic biological differences in neurodegeneration between the sexes is imperative. There is a lot of heterogeneity in the trajectory of Alzheimer’s symptoms, establishing sex differences in patterns of biology will lead to more targeted prevention and treatment mechanisms. It could be that women may need different treatment or different timing of treatment,” Rachel Whitmer, PhD, an epidemiologist at the University of California Davis, told Healthline.

It’s also something Buckley says needs to be considered during drug development.

“If there is a biological difference, we need to take this into account when running clinical trials. If men and women show differing levels of pathology, targeting pathology with drug treatments will show differing levels of efficacy by sex,” she said.

Until then, experts say women and men alike need to continue taking preventative measures against Alzheimer’s disease.

“For the time being, most preventative recommendations are similar between the sexes: Do regular aerobic exercise, eat a heart-smart/Mediterranean diet, minimize and aggressively treat vascular risk factors… hypertension, high cholesterol and diabetes,” Greicius said.

“The only potential difference between the sexes would pertain to the agonizing, ever-vacillating recommendations pertaining to hormone replacement after menopause. The current recommendation is that hormone replacement therapy (HRT) does not help prevent [Alzheimer’s disease] or other dementias and may increase the risk for all-cause dementia. These recommendations could change in the future once we have more detailed data,” he said.

Scientists are trying to determine why women are at greater risk of developing Alzheimer’s than men.

Researchers say it appears tau proteins, a primary factor in Alzheimer’s progression, grow more rapidly in women.

The researchers say figuring out why women are more susceptible to Alzheimer’s could lead to better treatments and preventative measures.