Why Alzheimer's Disease Is More Common In Women

Medical providers have long known that more women contract Alzheimer's disease (AD) than men. Until recently, many attributed this difference to female longevity. However, recent research has shown that multiple biological and social factors make women more vulnerable to AD.

It's not just a matter of women living longer. By age 65, 1 in 5 women has Alzheimer's, while only 1 in 11 men has the condition.

Biology Makes Women More Vulnerable to AD

1. Apolipoprotein E

Lipid biology is an essential factor in how AD impacts women more than men. The human body produces four Apolipoproteins (apoE1, apoE2, apoE3, and apoE4) that play a significant role in Alzheimer's disease.

The most interesting protein of the four is apoE4.

People with genes that code for apoE4 are more likely to contract Alzheimer's late in life. However, women with the apoE4 gene are more prone to AD than men with the same gene. Female apoE4 carriers are twice as likely to develop Alzheimer's as women who lack this gene. Conversely, male apoE4 carriers contract AD slightly more often than non-carriers.

Why epoE4 causes women to develop AD far more often than men isn't clear. Many researchers assume the difference has something to do with sex hormones, but exactly what role they play hasn't been explored. However, studies show that epoE4 carriers who use hormone replacement therapy (HRT) after menopause increase their AD chances. Meanwhile, female non-carriers lower their risk of AD by using HRT.

ApoE4 isn't the only lipoprotein that affects Alzheimer's. Both men and women who express the apoE2 gene show a reduced risk of AD.

Apolipoprotein E studies suggest genetic testing can play an important role in limiting AD risk. For example, determining whether or not a woman codes for the epoE4 gene can help medical providers create a treatment plan that reduces Alzheimer's risk.

2. Estrogen and Rat Mitochondria

ApoE4 biology isn't the only role estrogen plays in AD. Studies suggest that estrogen also can affect brain cells.

Mitochondria produces energy by converting glucose into adenosine triphosphate (ATP). Rats (and presumably people) who contract AD are also more likely to show reduced mitochondria function in the brain.

Studies show that estrogen seems to protect the mitochondria in the brain cells of female rats. Since mitochondria use oxygen to produce energy, mitochondria are exposed to high levels of 02. However, oxygen also can cause mutations in animal cells (known as "oxidative stress"). Estrogen apparently protects mitochondria from oxidative damage, which helps maintain energy production in the brains of female rats.

However, this protection wanes when estrogen levels decline in older female rats. These studies suggest that older female rats become more likely to suffer O2 damage, which causes a lack of energy in the brain, resulting in AD.

It's a chain reaction.

Why the mitochondria of male rats, who naturally produce only low estrogen levels, don't suffer the same risk of AD is unclear. Perhaps both male and female sex hormones protect mitochondria from AD. Since males don't experience menopause, their mitochondria could retain hormonal protection against oxidative stress their entire lives.

3. Depression Affects Women Differently Than Men

The hippocampus is the part of the brain responsible for retaining memories. When a person becomes depressed, studies show that the hippocampus shrinks.

In women, this shrinkage interferes with memory formation. However, it doesn't produce the same result in men.

Since women suffer from depression more often than men, they get hit with a double whammy. First, they are more likely to get depressed, and that depression is more likely to interfere with their memory.

4. Selection Bias

Both heart disease and diabetes are well-known risk factors for developing Alzheimer's. Men, however, are more likely to develop both conditions than women.

Both conditions also create a higher risk of early death.

Consequently, more men with AD are likely to die from either heart disease or diabetes before age 65 than women with AD. This reality creates a selection bias that causes a higher percentage of women to reach that age with Alzheimer's.

Social Factors That Increase AD Risk for Women

1. Exercise Less Than Men

Fitness plays a key role in staving off Alzheimer's. Clinical research shows high levels of fitness can reduce AD risk by as much as 88% compared to moderate fitness. However, women have historically been less likely to exercise than men.

This trend may be quite different in the coming years. In the past, our culture considered exercise "unfeminine," which discouraged many women from developing regular fitness routines. Since the 80s, this social belief has changed. As people from more recent eras advance into their elder years, the "exercise gap" will likely narrow.

The critical point is that people can drastically reduce their Alzheimer's risk with regular exercise. These studies also suggest that elderly people benefit from fitness training more than young people.

2. More Likely to Provide Elder Care

Many studies show that suffering stress increases the risk of developing AD. Obviously, caring for an elderly person is often a stressful experience. Far more elderly women become caregivers for their late-in-life family members than elderly men.

Our society needs to pay more attention to the mental health needs of caregivers. Further, the cultural expectations and gender role bias surrounding elder care need to change. For example, women feel more pressure to become caregivers and suffer more stress when they require care. This effect is known as "grateful guilt" and can compound the mental distress of elderly women.

3. Limited Education

Many studies show that regular mental exercise reduces the Alzheimer's risk. In earlier generations, women typically received less education than men. This lack of formal schooling meant elderly women were less likely to use abstract reasoning as they aged.

Even patients who show amyloid and tau deposits (proteins strongly correlated with AD) in their brain cells often will not develop the disease if they regularly use abstract reasoning.

This research suggests it's essential for elderly people to use their brains. Filling out crossword puzzles, reading, and playing complex card games like poker or bridge have all been associated with lower Alzheimer's risk. Holding a job that demands complicated decision-making can also help stave off AD.

The good news is that this education gap will close rapidly in the coming years. Currently, women earn 62% of all higher education degrees. In fact, in the future, we're likely to see this gap reverse and men lagging behind women in abstract reasoning.

4. Doctors Often Miss AD in Women

Medical providers screen for Alzheimer's using cognition tests that depend on verbal communication. Yet, women are typically better in this area than men.

Women buy 70% of all books sold in the United States. Women also show higher scores on communication and reading tests than men. This ability to use language can disguise the loss of cognitive ability in the tests doctors use to diagnose AD.

Failing to identify AD in the early stages can prevent effective treatment. Therefore, it's critical to slow down disease progression as early as possible. Unfortunately, doctors often miss this early treatment opportunity in women.

Women Must Guard Against Alzheimer's

Given the biological and social factors that make women more vulnerable to Alzheimer's, they must combat the disease with increased awareness. Regular exercise, solving puzzles, taking on complex mental tasks, testing improvements, and stress relief techniques can reduce women's risk of developing AD. However, these tools do little good if patients fail to use them.

The good news is that patients can do a lot to reduce Alzheimer's risk. For example, exercise alone can bring women's AD risk down to typical male levels.