Why is Alzheimer’s disease more prevalent in women?

Two-thirds of Alzheimer’s patients are women, and researchers are looking at multiple reasons why this is so.

It’s long been assumed the main reason is because women tend to live longer than men, and the risk of Alzheimer’s disease goes up with age. But other factors may be at work, including:

• Genetics
• Hormones
• Autoimmune conditions
• Amount of cognitive reserve

“I’m excited by the progress we’ve made, but we’ve got a lot of work to do” to fully understand Alzheimer’s disease and why it affects women differently, said Sean P. Horrigan, DO, medical director of Neurologists of Cape Cod in Hyannis.

Genetics

“Less than 3 percent of Alzheimer’s cases are directly inherited from parents through a single genetic mutation,” he said. However, because women have two X chromosomes compared with one in men, this allows for more genetic variability in women, which may increase their risk, he added.

The gene most strongly linked with a high risk of developing Alzheimer’s disease is called APOE, which is not on the X chromosome. About 75 percent of people carry a version (allele) called APOE E3, Dr. Horrigan said. It probably doesn’t increase the chances of developing Alzheimer’s, according to the National Institute on Aging (NIA). However, carrying a single copy from one parent of a form called APOE E4 can increase the risk one to two times, Dr. Horrigan said, and having a copy from both parents raises that risk 12 times. According to the NIA, about a quarter of the population has one copy of APOE E4 and 2-3 percent have two copies.

Hormones

A hormone called estradiol is extremely important to brain health, according to Dr. Horrigan. It is a form of the female hormone estrogen and influences many aspects of brain function, including higher cognitive function, according to a June 20, 2024 article in Nature: Scientific Reports. Drug therapy to restore estrogen levels that drop during perimenopause and menopause has been used to treat menopausal symptoms, such as hot flashes, but may also help preserve cognitive function and limit brain cell injury and death. The researchers wrote that it’s only effective if begun in midlife; waiting until damage has been done is too late. A September 10, 2024 article in The Cureus Journal of Medical Science said studies have associated menopause with a higher risk of Alzheimer’s disease. The protective effects of estrogen on women’s brains may include improving cardiovascular health.

Once used routinely, estrogen as hormone replacement therapy dropped after a 2002 release of findings from the Women’s Health Initiative that it increased chances of heart disease, stroke and breast cancer, according to an April 14, 2025 article from the Yale School of Medicine. The study’s methodology was later faulted, and hormone replacement therapy started below age 60 is now considered safe by many doctors, depending upon a woman’s health history, dose and delivery system. But not all agree, and hesitancy lingers among some women.

Autoimmune Conditions and Other Factors

Several other factors may contribute to women having an elevated chance of developing Alzheimer’s disease, Dr. Horrigan said.

For instance, women are 75 percent more susceptible to autoimmune disorders than men, he said. A March 18, 2025 article in Cell Reports Medicine looked at data from more than 300,000 people and found having one of 26 autoimmune conditions was associated with a heightened risk of developing Alzheimer’s disease, and the risk was higher for women. Indeed, some researchers propose Alzheimer’s may itself be an autoimmune disease, as described in a September 27, 2022 article in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association. A September 26, 2025 JAMA article looking at the higher incidence of Alzheimer’s in women quoted the 2024 Lancet Commission on Dementia as saying women have more risk factors than men, including higher rates of diabetes, depression, vision impairment, physical inactivity, poor sleep, social isolation and lower levels of education. Dr. Horrigan added that women also have a higher risk of hearing loss, which has been associated with developing dementia.

The same JAMA article also said some medical conditions raise the risks of cardiac and circulatory system disease more in women than men. Women also differ from men in one physical hallmark of Alzheimer’s disease: The accumulation of tau protein tangles in the brain, the article said. Citing a meta-analysis in JAMA Neurology, it said that among people who initially had high levels of amyloid beta, which forms plaques in the brain in Alzheimer’s patients, but were still cognitively normal, women accumulated tau tangles more quickly.

Another difference between the sexes: Men tend to die faster than women after diagnosis. The JAMA article said men die from all causes 24 percent more within one year of Alzheimer’s diagnosis than women.

A Neurologist’s Advice

According to Dr. Horrigan, women and men can lower their risk of developing Alzheimer’s or other forms of dementia by:

• Exercising regularly.
• Eating a healthy diet.
• Staying socially active.
• Wearing hearing aids if needed.
• Avoiding alcohol and tobacco.
• Taking up challenging hobbies in retirement.

Keeping the mind active in various ways helps build synaptic connections in the brain, thereby increasing cognitive reserve. Some individuals whose brains were examined after death showed no symptoms of Alzheimer’s yet had elevated levels of amyloid beta, a hallmark of the disease. He suggested that these individuals may have protected their minds through a substantial cognitive reserve.

What to Do

If someone is showing signs of mental decline, such as getting lost on the way home from running an errand or forgetting familiar things, the first step would be to see their family physician for a mental status exam, Dr. Horrigan said. The doctor could then refer the patient to a neurologist. It's helpful if a spouse or family member accompanies the patient.

“It’s important to consider their perspective as well,” Dr. Horrigan said. “Most of the time, an accurate diagnosis depends largely on the patient's story. It's essential to truly understand what is happening in their world.”

He recommends that family members write a letter or email ahead of the visit to avoid having to broach sensitive topics during the appointment. Blood tests and brain imaging may be conducted to confirm or rule out an Alzheimer’s diagnosis. Dr. Horrigan added that, for female patients, he might also consult their obstetrician or gynecologist for additional input.