Alzheimer's Disease: Epidemiological Data, Symptoms and Causes

Alzheimer's disease is a progressive neurological disorder that leads to memory loss and cognitive decline and eventually impairs the ability to carry out daily tasks. It is the most common cause of dementia, which is a general term for a decrease in mental ability severe enough to interfere with daily life. Alzheimer's typically affects older adults, though it can occur in younger individuals (referred to as early-onset Alzheimer's).

The brain changes associated with Alzheimer's include the buildup of proteins called beta-amyloid plaques and tau tangles. These disrupt normal brain cell function, leading to cell death. Brain shrinkage, or atrophy, occurs as the disease progresses, particularly in areas responsible for memory and cognition.

Alzheimer’s epidemiological data

Approximately 55 million people worldwide are living with dementia, and Alzheimer’s disease accounts for about 60-70% of these cases. This means roughly 33 to 38.5 million people globally are affected by Alzheimer’s. Around 10 million new cases of dementia are diagnosed each year. This equates to one new case every 3.2 seconds. By 2050, the number of people living with dementia, including Alzheimer’s, is projected to rise to 139 million, primarily due to aging populations, especially in low- and middle-income countries.

Alzheimer’s disease risk increases significantly with age. While around 10% of individuals over 65 have Alzheimer’s, nearly 33% of people over 85 have the disease. Alzheimer’s is more common in women than in men, with women making up about two-thirds of Alzheimer’s cases. This may be due in part to the longer average lifespan of women.

In high-income countries, the prevalence of Alzheimer’s is relatively high due to the more significant proportion of older adults. In the United States alone, over 6 million people are currently living with Alzheimer’s, with this number expected to double by 2050.

Alzheimer’s is one of the leading causes of death globally. In the U.S., it ranks as the 6th leading cause of death overall and the 5th leading cause for adults aged 65 and older.

Alzheimer’s symptoms

Early Stage (Mild)

In the early stage, symptoms may be subtle and easily mistaken for typical age-related changes. Common symptoms include:

Memory Loss: Difficulty recalling recent events, appointments, or information. Memory lapses are often the first noticeable symptom.
Difficulty Planning or Solving Problems: Struggling to manage finances or work with numbers.
Poor Judgment: Making uncharacteristic decisions or showing reduced awareness of risks and safety.
Language Problems: Difficulty finding the right words or repeating themselves in conversations.
Disorientation in Familiar Places: Getting lost in familiar environments or forgetting routes.
Mood Changes: Depression, irritability, and anxiety may emerge as early signs, alongside a tendency to withdraw from social activities.

Middle Stage (Moderate)

Symptoms become more pronounced in this stage, and assistance with daily tasks is often needed:

Increasing Memory Loss and Confusion: Forgetting personal history, details about family members, or where they are. They may also lose track of the time or day.
Difficulty Recognizing Friends and Family: They may recognize faces but struggle to remember names or relationships.
Difficulty with Language and Communication: They may have trouble following conversations, understanding context, or finding words.
Problems with Spatial Relationships: Difficulty judging distances, depth perception, or recognizing objects, leading to increased risk of accidents.
Repetitive Behavior: Asking the same questions repeatedly or engaging in repetitive actions.
Changes in Sleep Patterns: Increased daytime sleepiness, difficulty sleeping at night, or confusion between day and night.
Increased Personality and Behavioral Changes: Agitation, suspicion, aggression, and impulsivity may arise, along with more frequent mood swings.
Loss of Independence in Personal Care: Difficulty dressing, bathing, or using the restroom without assistance.

Late Stage (Severe)

In this stage, the person is entirely dependent on caregivers and may have significant physical and cognitive impairments.

Severe Memory Loss: Inability to recognize close family members, friends, or even themselves in a mirror.
Loss of Ability to Communicate: Verbal skills become limited to single words or sounds, and nonverbal communication becomes the primary mode of expression.
Decline in Physical Abilities: Loss of mobility and control over bodily functions—difficulty swallowing, sitting, or even holding up one’s head.
Vulnerability to Infections: Due to immobility and weakened immune function, there is an increased risk of infections, especially pneumonia.
Loss of Awareness of Surroundings: People may no longer recognize their environment or people around them.
Extreme Personality and Mood Changes: The person may become anxious or fearful or display inappropriate emotional responses.

Behavioral and Psychological Symptoms Across Stages

Throughout the disease, people with Alzheimer’s may also experience a range of behavioral and psychological symptoms, including:

Depression and anxiety
Apathy and social withdrawal
Irritability and agitation
Hallucinations or delusions (typically in later stages)

Alzheimer’s causes

Alzheimer's disease is believed to result from a complex combination of genetic, environmental, and lifestyle factors that affect the brain over time. Although the exact causes are not fully understood, several key factors contribute to the development of Alzheimer’s disease.

1. Genetic Factors

Family History: A family history of Alzheimer’s increases an individual's risk, suggesting a genetic component. Those with a parent or sibling with Alzheimer’s are at a higher risk of developing the disease.
Genes: Certain genetic mutations are linked to Alzheimer’s:

-APOE ε4: This is the most well-known genetic risk factor for late-onset Alzheimer’s (typically occurring after age 65). People who inherit one copy of the APOE ε4 gene have an increased risk, while those with two copies have an even higher risk.

-Early-Onset Genetic Mutations: In rare cases, specific gene mutations (in the APP, PSEN1, and PSEN2 genes) lead to early-onset Alzheimer’s, which can develop in people as young as their 30s or 40s.

2. Amyloid and Tau Proteins

Beta-Amyloid Plaques: In Alzheimer’s, beta-amyloid protein fragments accumulate and clump together between neurons, forming plaques. These plaques interfere with cell-to-cell communication and may trigger an immune response that damages brain cells.
Tau Tangles: Inside neurons, tau proteins typically help stabilize structures called microtubules. In Alzheimer’s, tau proteins become abnormally altered and form tangles, which disrupt nutrient and signal transport within cells, ultimately leading to cell death.

3. Age-Related Changes in the Brain

Brain Shrinkage: Some brain areas naturally shrink with age, impacting memory and cognitive functions. In Alzheimer’s, this shrinkage is more pronounced.
Inflammation: As we age, the brain may experience increased inflammation due to a less efficient immune system, which can lead to cell damage. In Alzheimer’s, this inflammatory response is often heightened and contributes to the disease’s progression.
Mitochondrial Dysfunction: Mitochondria are cell structures responsible for energy production. In Alzheimer’s, mitochondrial function is impaired, leading to lower neuron energy levels and increased vulnerability to damage.

4. Cardiovascular Health

Conditions that affect heart health, such as high blood pressure, high cholesterol, and diabetes, also impact brain health. Reduced blood flow to the brain can lead to damage in blood vessels, increasing the risk of Alzheimer’s.
Atherosclerosis: This condition, where arteries harden and narrow due to plaque buildup, can reduce blood flow to the brain, affecting its function and increasing the risk of Alzheimer’s.

5. Lifestyle and Environmental Factors

Physical Inactivity: A sedentary lifestyle is associated with a higher risk of Alzheimer’s. On the other hand, regular physical activity promotes blood flow to the brain, supporting overall brain health.
Diet: Diets high in refined sugars and processed foods may increase Alzheimer’s risk, while diets rich in antioxidants, omega-3 fatty acids, and whole foods (such as the Mediterranean diet) may reduce it.
Social Engagement and Mental Stimulation: Limited social interaction and mental activity are linked to a higher risk of cognitive decline. Staying socially and mentally active helps build cognitive reserve, potentially delaying symptoms of Alzheimer’s.
Education and Cognitive Reserve: Studies suggest that people with higher education levels and cognitively stimulating lifestyles are at lower risk. Cognitive reserve—the brain’s ability to compensate for damage—may delay the onset of symptoms.

6. Head Trauma

Severe or repeated head injuries are linked to a higher risk of Alzheimer’s. Head trauma can trigger a cascade of events that may accelerate the formation of amyloid plaques and tau tangles.

7. Sleep Patterns

Poor sleep quality, particularly sleep disorders such as sleep apnea, has been associated with a higher risk of Alzheimer’s. Sleep is essential for clearing beta-amyloid from the brain, and chronic sleep issues may contribute to the buildup of these harmful proteins.

8. Chronic Inflammation and Immune Response

Chronic inflammation may play a role in Alzheimer’s development. In some cases, the body’s immune response to plaque formation triggers an inflammatory reaction, which leads to neuron damage.

Ongoing Research and Emerging Factors

Researchers continue to explore other possible contributing factors, including viral infections (like herpes simplex virus), exposure to toxins, gut microbiome imbalance, and hormonal changes, which may also play roles in Alzheimer’s development.

Alzheimer’s appears to be caused by a multi-factorial interaction of these elements rather than a single factor alone. Understanding these causes and risk factors has been essential in developing preventive and therapeutic strategies.

Alzheimer's functional medicine root causes

In functional medicine, Alzheimer's disease is approached through the lens of underlying root causes, looking beyond symptoms to identify and address the body-wide imbalances that may contribute to the disease’s development. Here are some of the primary root causes from a functional medicine perspective:

1. Chronic Inflammation

Systemic Inflammation: Ongoing, low-grade inflammation throughout the body has been linked to an increased risk of Alzheimer’s. This inflammation can stem from infections, autoimmune conditions, chronic stress, or an unhealthy lifestyle.
Neuroinflammation: Inflammation, specifically in the brain, can damage neurons and impair brain function. It’s thought to be triggered by factors like infections, toxic exposures, and immune responses, contributing to the formation of amyloid plaques and tau tangles characteristic of Alzheimer’s.
Gut Health and Dysbiosis: Gut health is closely linked to inflammation and brain health. Imbalances in gut bacteria (dysbiosis) can lead to increased intestinal permeability ("leaky gut") and promote systemic inflammation. This gut-brain axis connection is crucial, as inflammation originating in the gut can influence brain health.

2. Hormonal Imbalances

Insulin Resistance and Blood Sugar Dysregulation: Known as “Type 3 diabetes” by some experts, Alzheimer’s has a strong link with insulin resistance. High blood sugar and insulin resistance impair brain cells’ ability to metabolize glucose, leading to cognitive decline. Elevated blood sugar can also increase inflammation and oxidative stress.
Thyroid and Adrenal Health: Thyroid dysfunction can affect brain health, and adrenal imbalances caused by chronic stress can lead to hormone imbalances, including cortisol, which negatively impacts memory and cognitive function.

3. Nutritional Deficiencies

Antioxidants: Deficiencies in antioxidants like vitamins C and E and glutathione reduce the body’s ability to fight oxidative stress, which damages brain cells and accelerates brain aging.
B Vitamins: B vitamins, especially B6, B12, and folate, are crucial for cognitive health. Low levels of these vitamins are associated with elevated homocysteine, an amino acid linked to increased Alzheimer’s risk.
Omega-3 Fatty Acids: Omega-3s, particularly DHA, are essential for brain cell membranes and cognitive function. Deficiencies in omega-3s can increase inflammation and reduce neuroplasticity, which is the brain's ability to adapt and form new neural connections.

4. Toxic Exposures

Heavy Metals: Exposure to heavy metals like mercury, lead, and aluminum has been associated with neurodegenerative changes. These metals can accumulate in the brain, causing oxidative stress and neuronal damage.
Environmental Toxins: Toxins such as pesticides, air pollutants, and industrial chemicals can have neurotoxic effects. Chronic exposure to these environmental toxins is linked to inflammation and oxidative stress in the brain.
Mycotoxins: Mold produces mycotoxins, which can harm the brain and nervous system. For people with chronic mold exposure or mold sensitivity, mycotoxins can lead to cognitive symptoms and increase their risk of Alzheimer’s.

5. Oxidative Stress

Oxidative stress occurs when there is an imbalance between free radicals and the body's antioxidant defenses. In the brain, oxidative damage leads to neuron dysfunction and death. Factors contributing to oxidative stress include a diet low in antioxidants, pollution, smoking, and inflammation. Oxidative stress is a key driver in the buildup of amyloid plaques and tau tangles in Alzheimer’s.

6. Mitochondrial Dysfunction

Mitochondria, the energy-producing structures in cells, are crucial for brain function. Mitochondrial dysfunction can reduce energy production and increase free radical damage, leading to neuronal death. In Alzheimer’s, mitochondrial dysfunction impairs cognitive abilities and accelerates brain aging.

7. Impaired Detoxification Pathways

The body’s ability to detoxify can influence brain health. When the liver, kidneys, and lymphatic systems are overwhelmed, or under-functioning, toxins, and metabolic waste can accumulate, contributing to brain inflammation and oxidative stress. A poor diet, dehydration, chronic illness, and exposure to environmental toxins can all impact detoxification pathways.

8. Chronic Infections

Viral Infections: Chronic infections, such as herpes simplex virus type 1 (HSV-1), have been found in brain tissue of some Alzheimer’s patients, suggesting an infectious component to the disease. Infections can trigger chronic immune activation and inflammation in the brain.
Bacterial Infections: Conditions like periodontal disease can contribute to inflammation and immune system dysregulation, increasing the risk of Alzheimer’s.
Fungal Infections: Fungal infections or mold exposure may also affect neuroinflammation. Emerging research suggests that the brain may harbor fungal cells in Alzheimer’s, potentially contributing to plaque formation.

9. Genetic Susceptibility and Epigenetics

Genetic Risk Factors: Specific genes, like APOE ε4, increase Alzheimer’s risk. However, functional medicine emphasizes that lifestyle and environmental factors can influence gene expression (epigenetics). By addressing diet, lifestyle, and environmental factors, individuals may reduce the risk associated with genetic susceptibility.
Epigenetic Modifications: Through diet, exercise, and toxin reduction, individuals can influence their genetic expression, potentially mitigating Alzheimer’s risk even in those with genetic predispositions.