African Americans and Alzheimer’s disease

Alzheimer’s disease is characterized by misfolded proteins including amyloid and tau—but it is a complex disease that often involves other problems in the brain, such as problems with blood vessels, inflammation, or metabolic dysfunctions. Because of its complex nature, Alzheimer’s disease does not affect all groups of people equally. We previously discussed how Alzheimer’s disease affects women differently from men. Here, we discuss how African Americans are impacted by Alzheimer’s disease differently from other ethnicities.

African American’s are at a greater risk for Alzheimer’s disease… but it is complicated

It is estimated that African Americans are about twice as likely as Caucasians to develop Alzheimer’s disease [1], although, once diagnosed, they may experience slower cognitive decline [2]. But some of these findings have caveats as they come from observational studies which enroll patients residing in specific geographic locations, and therefore may not apply to the rest of the US [3]. For example, one population-based study looked at all hospital health records from individuals in the Kaiser Permanente Northern California health care system, which included over 3 million people. They found that African Americans have only a 40% greater dementia risk compared to Caucasians [4].

Results are also variable depending on the methods used for the diagnosis of Alzheimer’s disease, which may alter the true Alzheimer’s rate in a population [5][6]. Disparities in years of education or socioeconomic status, especially in elderly African Americans, also affect the scores on dementia tests. One study administered a battery of cognitive tests to individuals living in Baltimore, Maryland. Although African Americans on average scored lower than Caucasians, this difference was significantly diminished after controlling for socioeconomic status [7].

Why might African Americans be at a greater risk for Alzheimer’s disease?

Several factors could partly explain the elevated risk of Alzheimer’s disease in African Americans. For instance, African Americans have higher rates of cardiovascular risk factors such as hypertension (high blood pressure) and diabetes, which are also risk factors for Alzheimer’s disease [8][9]. Hypertension over time may damage the blood vessels in the brain, which can starve the brain of oxygen and vital nutrients for the brain to function properly. Diabetes also affects how well the brain uses glucose, its main fuel source. These changes in the brain can cause lower scores on cognitive tests and contribute to the elevated Alzheimer’s risk.

Another important risk factor is APOE4, a genetic risk factor for Alzheimer’s disease. There are three variants of APOE (2, 3, 4) and each person has two copies. Having one or two copies of APOE4 increases the risk of Alzheimer’s disease in Caucasians compared to having two copies of APOE3. Several studies suggest that APOE4 is more prevalent in African Americans than in Caucasians [10; 11; 12]. Intriguingly, whether APOE4 increases the risk of Alzheimer’s disease in African Americans is unclear. Some studies show that APOE4 does not increase Alzheimer’s risk in African Americans [11; 13] while others suggest it does [14; 15; 16].

Finally, one theory suggests that African Americans are especially vulnerable to the wear and tear that comes with chronic stress due to factors such as socioeconomic status, discrimination, or psychological stress. This chronic stress could be a risk factor for cognitive decline [17]. When someone is in a dangerous or stressful situation (“fight or flight” response), the body releases stress hormones that increase fuel and blood flow to the muscles while suppressing the immune system. Usually, the body returns to its normal state after the stressor is gone. However, chronic stress that comes from low socioeconomic status, discrimination, or psychological stress may decrease the body’s ability to return to its normal state, and this wear and tear increases with age. Chronic stress may be associated with several negative health outcomes such as hypertension, diabetes, cardiovascular disease, and memory impairment [17; 18].

More research is needed to better understand how Alzheimer’s disease affects African Americans

One reason we know relatively little about how Alzheimer’s affects minority populations is that they are underrepresented in Alzheimer’s disease studies. For instance, it was reported that in 18 observational studies and clinical trials, only 7% of the Alzheimer’s participants were African American [19]. Increasing minority enrollment in observational studies will allow us to gain a better understanding of how Alzheimer’s affects minority populations and which interventions are most effective for each population. It is also important to enroll more minorities in clinical trials as different ethnicities may respond to drugs in different ways. For instance, several studies on anti-hypertensives found that Caucasians responded better to one class of drugs (i.e., β-blockers) while African Americans responded better to another class (i.e., diuretics) [20].

The good news is that there are efforts underway to increase Alzheimer’s research in African Americans. On October 10^th, 2018, the National Institute on Aging convened a meeting to discuss how to increase African American participation in research studies. The Washington University Alzheimer’s Disease Research Center discussed a success story. They established an African American Advisory Board in 2000. Since then African American representation at Washington University studies increased from 3% to 18%. With more efforts like these, we look forward to gaining a better understanding of how Alzheimer’s affects African Americans differently from other populations.

How can one reduce the risk of Alzheimer’s disease?

Although there is evidence that African Americans may be at a greater risk of Alzheimer’s disease, the good news is that there are steps everyone can take to reduce their risk. We recommend seven steps for brain health, including eating a healthy diet, sleeping well, exercising, alleviating stress, being social, continuing to learn, and managing chronic illnesses.

Since African Americans have a higher incidence of cardiovascular risk factors, they may gain greater benefit from interventions that promote cardiovascular health, such as diet, exercise, and medications to treat high blood pressure or diabetes (e.g., antihypertensive or antidiabetic drugs, respectively). Increased African American participation in research studies will help reveal which risk reducing strategies are most effective. For instance, studies show that greater adherence to diets, such as the Mediterranean diet, prevents cognitive decline in African Americans [21; 22]. It is never too early to start taking care of your brain because even our lifestyle choices in midlife can change our risk trajectory.

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