Researchers have concluded that Alzheimer’s disease likely does not have a single cause. Instead, several risk factors, including genetics, lifestyle and environment, contribute to the brain’s health and pathology. Below are these contributing factors.
AGE
“Alzheimer’s is not a term for brain aging: it is not normal.”
—Meg Smith, CEO, Cure Alzheimer’s Fund
While Alzheimer’s is a disease of aging, it is not a natural part of the aging process. Still, aging is the most significant risk factor for Alzheimer’s disease. Less than 10% of all known cases begin before the age of 65. However, at age 65, the risk of developing Alzheimer’s doubles roughly every five years, reaching almost 50% by age 85. Research on age-related factors contributing to the disease includes neuroinflammation, blood vessel damage, aging of the blood-brain barrier and increased vulnerability of specific brain areas. To learn more, read about in-depth studies here and on this page.
GENETICS
Our genetics may contribute to—or protect against—Alzheimer’s disease. As an example, the APOE gene is known to have a role in Alzheimer’s disease. APOE2 is recognized as protective for the disease, while the greatest genetic risk factor for sporadic Alzheimer’s is the APOE4 gene variant. Researchers estimate that 15% to 20% of the population carries the APOE4 gene, inherited from our biological parents. Having one copy of APOE4 increases the risk for Alzheimer’s about three to four times, and having two copies (one from each parent) increases the risk up to 12 times. It is important to know that having one or two copies of APOE4 does not guarantee that the disease will develop.
There are a number of other genes known to have a relationship with Alzheimer’s disease, and researchers are studying new candidates for their role in the disease. Visit this page to learn more about the genetics of Alzheimer’s disease.
SEX
Women are diagnosed with Alzheimer’s disease at a greater rate than men; some studies have estimated that up to two out of every three Alzheimer’s disease patients are women. In fact, the first person ever diagnosed with Alzheimer’s disease—Auguste Deter—was a woman. While women, on average, live longer than men, longevity alone does not account for the disparate impact of Alzheimer’s on women. Why women are disproportionately affected compared with men, and the study of sex-based differences, is essential to developing future therapies. Follow this link to learn more about the research discoveries in understanding the role of sex-based differences.
LIFESTYLE AND ENVIRONMENTAL FACTORS
Alzheimer’s disease risk factors include age, genetics, environment, behavior, and individual experiences and lifestyle factors. Although one’s genetics and age cannot be changed, some risk factors are modifiable, and may reduce the risk of dementia and improve our brain health.
FROM THE NATIONAL INSTITUTES OF HEALTH AND THE NATIONAL INSTITUTE ON AGING:
“Research suggests that a host of factors beyond genetics may play a role in the development and course of Alzheimer’s disease. There is a great deal of interest, for example, in the relationship between cognitive decline and vascular conditions such as heart disease, stroke, and high blood pressure, as well as metabolic conditions such as diabetes and obesity. Ongoing research will help us understand whether and how reducing risk factors for these conditions may also reduce the risk of Alzheimer’s.”
EXERCISE
A low level of physical activity is a known modifiable risk factor for dementia, including Alzheimer’s disease, so people should stay active in mid-life and late life as part of an overall health plan. Studies show that increasing levels of exercise can delay cognitive loss or improve cognitive functions in humans as well as mouse models of Alzheimer’s disease. To learn more about the impact of exercise, please read about the research uncovering its benefits here, its protective power here, and how it may stimulate the birth of new neurons in the brain here.
DIET
Studies suggest that a diet low in saturated fats and processed sugar with higher levels of unsaturated fats is associated with lower risk of developing cognitive decline. An example of such a diet is the Mediterranean diet. To learn more, read about the research on the benefits and drawbacks of certain diets.
SLEEP
As we age, our sleep/wake cycle changes and older adults sleep less and less. Many studies show that quality sleep is essential to the health of our brains. During sleep, the brain performs cleaning processes and removes unwanted debris and toxins that build up during normal brain function while awake. These maintenance functions during sleep are crucial for brain health. Researchers have long suspected a direct link between poor-quality sleep and Alzheimer’s disease. Both are associated with deficits in cognition, and sleep disturbances are common in Alzheimer’s patients. To learn more, read about the research into Alzheimer’s disease and sleep and watch our webinar.
STRESS
You might not think twice if someone told you that eating healthy, getting enough sleep and managing stress can significantly reduce your risk of a heart attack. Now, emerging evidence suggests that high stress levels may also cause changes in the brain, contributing to cognitive decline and Alzheimer’s disease. Read more here.
POLLUTION
Multiple studies have tied components of air pollution to accelerated cognitive decline and increased risk of Alzheimer’s and dementia. Several studies funded by Cure Alzheimer’s Fund have provided insights into the potential negative impact of pollution on the health of our brains. To learn more, read about the discoveries here and visit this page for a historical overview exploring the connection between the disease and environmental pollutants.
EDUCATION AND CONTINUED LEARNING
Studies show that higher levels of education during childhood and young adulthood, such as completing high school and college, along with continuous learning throughout life, may reduce the risk of developing dementia. Engaging in challenging cognitive activities can help form new synapses in the brain’s neural networks and potentially improve overall brain health. Stimulating the brain with such activities may build cognitive reserve—the brain’s capacity to utilize flexible pathways that allow a person to function despite the changes caused by Alzheimer’s disease. Researchers believe a strong cognitive reserve may enhance the brain’s resilience to Alzheimer’s pathology.
SOCIAL ENGAGEMENT
As we enter our senior years, staying socially active may be more difficult and isolation can become common. However, research shows that staying socially active and engaged is important to the health of our bodies and our brains. The National Institute on Aging offers a toolkit to reduce social isolation and loneliness. Find it here.
CARDIOVASCULAR HEALTH
Researchers increasingly recognize the vascular contributions to Alzheimer’s disease, suggesting that damage to the brain’s blood vessels may be one of the earliest markers of the condition. Many risk factors for cardiovascular disease also are risk factors for Alzheimer’s. These include hypertension, high LDL cholesterol, low HDL cholesterol, obesity and diabetes. Smokers are at higher risk of heart disease and dementia than nonsmokers. Even if done at an older age, eliminating the habit of smoking reduces risk for cardiovascular and brain maladies. Excessive alcohol consumption is also a modifiable risk factor for heart disease and dementia, and reduction in alcohol intake lowers the risk for both.
Scientists may discover other risk factors for Alzheimer’s disease over time. For those risk factors where we have some control, implementing changes may have positive benefits for our hearts and our brains.