Alzheimer’s is a disease that affects many individuals, yet the cause is uncertain and a cure is undiscovered. Alzheimer’s Disease is a type of dementia characterized by memory loss, mood and behavioral changes, as well as decreased function in activities of daily life. While the exact cause is uncertain, there are factors thought to be associated with Alzheimer’s Disease. Age, sex, physical activity level, social activity level, cognitive stimulation, diet, genetics, heart health, and brain injury are all factors thought to be associated with Alzheimer’s disease. While the “old school” pathophysiological theory of Alzheimer’s Disease posited memory loss to be caused by plaques and tangles, more modern research suggests plaques and tangles to be a mere byproduct of the mechanisms truly causing memory loss. The following article will provide a comprehensive overview of Alzheimer’s Disease, which includes defining the disease, presenting various ways the disease is broken down and understood, detailed information on the factors associated with Alzheimer’s Disease, signs and symptoms of the disease in comparison to typical age-related changes, up-to-date theories on brain processes associated with Alzheimer’s Disease, Alzheimer’s Disease diagnostic criteria, behavior abnormalities associated with some cases of Alzheimer’s Disease, as well as caregiver resources and how to proceed if you think you may have Alzheimer’s Disease, or if you have recently been diagnosed.
Understanding Alzheimer’s Disease
Alzheimer’s Disease is a subtype of dementia. To understand Alzheimer’s, one must understand dementia. According to the National Institute of Health (2023), dementia is a general term that refers to nerve cells not working properly, which leads to impairment in thinking, remembering, reasoning, and functioning in daily activities, as well as changes to personality and behavior. There are specific types of dementia which include Alzheimer’s Disease, frontal-temporal, lewy-body, and vascular dementia. A person may have just one type or they may have several types. In people 85 and older, one out of every three people is diagnosed with dementia, but it is not a normal part of aging.
The NIH defines dementia generally, but they also present some specific patterns of dementia. These patterns include:
- Experiencing memory loss, poor judgment, and confusion
- Difficulty speaking, understanding and expressing thoughts, or reading and writing
- Wandering and getting lost in a familiar neighborhood
- Trouble handling money responsibly and paying bills
- Repeating questions
- Using unusual words to refer to familiar objects
- Taking longer to complete normal daily tasks
- Losing interest in normal daily activities or events
- Hallucinating or experiencing delusions or paranoia
- Acting impulsively
- Not caring about other people’s feelings
- Losing balance and problems with movement
Image 1. Alzheimer’s Association, 2023.
While the exact cause of Alzheimer’s Disease is unknown at this time, it is agreed upon that Alzheimer’s Disease is characterized by damaged nerve cells without a known, direct cause. In autopsies, individuals with Alzheimer’s Disease had particular patterns of plaques and tangles in the brain that differed from individuals who had not been diagnosed with Alzheimer’s Disease (Alzheimer’s Association, 2023). The Alzheimer’s Association (2023) presents, “10 Early Signs and Symptoms of Alzheimer’s” as well as a comparison between the signs and symptoms of Alzheimer’s vs. typical age related changes. The, “10 Early Signs and Symptoms of Alzheimer’s” include:
- Memory loss that disrupts daily life
- Challenges in planning or solving problems
- Difficulty completing familiar tasks
- Confusion with time or place
- Trouble understanding visual images and spatial relationships
- New problems with words in speaking or writing
- Misplacing things and losing the ability to retrace steps
- Decreased or poor judgment
- Withdrawal from work or social activities
- Changes in mood and personality
Many individuals may wonder where the line is drawn between typical age-related changes and signs and Alzheimer’s and dementia. Overall, the distinguishing factor between the disease and typical aging appears to be a pattern of cognitive difficulty versus occasional cognitive difficulty. The Alzheimer’s Association (2023) presents a table to help distinguish between Alzheimer’s Disease and typical aging.
Image 2. Alzheimer’s Association, 2023.
Alzheimer’s is not a stagnant disease. Overtime, Alzheimer’s Disease worsens and becomes more severe. Disease progression is important to understand, which is why clinical research is so important. The University of Michigan (2023) presents Alzheimer’s Disease on a continuum, which ranges from preclinical Alzheimer’s Disease to severe Alzheimer’s Disease. In this perspective, Alzheimer’s Disease ranges from preclinical, to mild cognitive impairment, mild, moderate, and ultimately severe Alzheimer’s Disease. Preclinical Alzheimer’s Disease is characterized by no symptoms. Mild cognitive impairment due to Alzheimer’s Disease presents as very mild symptoms that do not interfere with everyday activities. Mild Alzheimer’s Disease includes symptoms which interfere with some everyday activities. Moderate Alzheimer’s Disease includes symptoms which interfere with many everyday activities. Finally, Severe Alzheimer’s Disease is characterized by symptoms which interfere with most everyday activities.
Image 3. University of Michigan, 2023.
Further, Alzheimer’s Disease can be viewed in stages. The Alzheimer’s Association (2023) breaks Alzheimer’s Disease into three stages: Early, Middle, and Late. The early stage may include commonly include difficulties such as coming up with the right word or name, remembering names when introduced to new people, having difficulty performing tasks in social or work settings, forgetting material that was just read, losing or misplacing a valuable object, and/or experiencing increased trouble with planning and organizing. The middle stage may include being forgetful of events or personal history, feeling moody or withdrawn, especially in socially or mentally challenging situations, being unable to recall information about themselves like their address or telephone number, and the high school or college they attended, experiencing confusion about where they are or what day it is, requiring help choosing proper clothing for the season or the occasion, having trouble controlling their bladder and bowels, experiencing changes in sleep patterns, such as sleeping during the day and becoming restless at night, showing an increased tendency to wander and become lost, and/or demonstrating personality and behavioral changes, including suspiciousness and delusions or compulsive, repetitive behavior like hand-wringing or tissue shredding. The late stage may require around-the-clock assistance with daily personal care, loss of awareness of recent experiences as well as their surroundings, experience changes in physical abilities, including walking, sitting, and eventually swallowing, difficulty communication, and/or increased vulnerability to infections, especially pneumonia.
Factors Associated with Alzheimer’s Disease
The factors associated with Alzheimer’s Disease can be divided into two categories: risk and protective. These two categories are not mutually exclusive. Most of these factors are categorized as risk factors when they are neglected and protective factors when they are given time, energy, and consideration. Of course, there is no exact, known cause of Alzheimer’s Disease, and no surefire way to prevent Alzheimer’s Disease. According to The National Institute of Health (2023), there are no foolproof prevention strategies, but early intervention is key. Research on preventative strategies is encouraging but inconclusive.
Risk factors associated with Alzheimer’s Disease include genetics, sex, age, family history, head injury, and poor heart health (Alzheimer’s Association, 2023). Females and those aged 65 and up are at an increased risk of developing Alzheimer’s Disease (Alzheimer’s Association, 2023). Head injury, uncontrolled high blood pressure, diets high in sodium, sugar, processed food, and simple carbohydrates, sedentary lifestyles, family members with Alzheimer’s Disease, and APOE 4 genetic markers are all factors associated with an increased risk of developing Alzheimer’s Disease (Richard Johnson, MD; University of Michigan; Alzheimer’s Association, National Institute of Health, 2023).
Image 4. Alzheimer’s Association, 2023.
Protective factors may include cognitive training and blood pressure management. Cognitive training includes activities that strengthen problem solving, memory, and speed of processing pathways. You can access a cognitive training resource here BRAIN BOOSTING ACTIVITIES. Further, individuals with higher levels of education and more social engagement seem to have a correlation with an increase in preserved cognitive function. It is commonly said, “What’s good for the heart is good for the brain.” Blood pressure management early in life is a protective factor in Alzheimer’s Disease. Although diet and exercise are important at every stage of life, early adulthood seems to be a particularly important stage in connection to Alzheimer’s Disease. In terms of physical activity, aerobic exercise and strength training seem to be most beneficial in preserving cognitive function. However, the most important physical activity factor is not living a sedentary lifestyle. An individual would be advised to at least incorporate regular walking into their lifestyle if there is a concern for brain health. In terms of diet, one researcher is coming to the forefront of understanding Alzheimer’s Disease with research on metabolism and Alzheimer’s Disease. Dr. Richard Johnson suggests a link between sugar and impaired cognitive function (2023).
Pathophysiology of Alzheimer’s Disease
Pathophysiology refers to physiological processes associated with disease or injury. At this time, there is pathophysiology known to be associated with Alzheimer’s Disease, but knowledge of the pathophysiology causing Alzheimer’s Disease is still at a theoretical understanding level. As presented by the National Institute on Aging in their video, “How Alzheimer’s Changes the Brain” (2017), there are two main physiological processes associated with Alzheimer’s Disease pathology: protein buildup and chronic inflammation.
In healthy brains, neurons communicate with one another through electrical charges. These electrical charges travel through axons and cause the release of chemicals to other neurons. Microglia and astrocyte cells clear away debris and help keep neurons healthy. In Alzheimer’s Disease, the first noteworthy physiological process includes abnormal amounts of Tau and amyloid beta proteins present in the brain. Tau proteins accumulate and cause tangles inside of neurons and beta-amyloid protein clumps into plaques between neurons. The second noteworthy physiological process includes the vascular system. It is thought the vascular system may fail to deliver blood and other nutrients to the brain. The brain then lacks glucose needed to power its activity. Chronic inflammation sets in as microglial cells fail to clear away debris and astrocytes react to distressed microglia, causing neurons to lose their ability to communicate. As neurons die, the brain shrinks. Brain shrinkage begins in the hippocampus, a part of the brain responsible for learning and memory (NIA: How Alzheimer’s Changes the Brain, 2017).
Diagnosing Alzheimer’s Disease
Diagnosing Alzheimer’s Disease tends to lean toward a “process of elimination” approach due to the nature of the disease. Typically, Alzheimer’s Disease cannot be diagnosed until symptoms are present. This is because genetic biomarkers of the disease may be present in someone who never develops Alzheimer’s Disease, and they may not be present in someone who does have Alzheimer’s Disease. Alzheimer’s Disease is diagnosed through a combination of imaging, laboratory values, and symptomatology. In addition, genetic testing can be used to predict the likelihood of an individual developing Alzheimer’s Disease, as well as help confirm an existing diagnosis.
Magnetic Resonance Imaging (MRI) is a tool used to rule other other causes of memory loss. Presence of tumor, stroke, lacunar infarcts, traumatic brain injury, or vascular disease may provide neurologists with information about the source of the memory loss. However, the lack of this presence, typically in combination with hippocampal shrinkage, is one piece of information that indicates Alzheimer’s Disease as the diagnosis.
Although tau and amyloid-beta protein levels were once thought to cause Alzheimer’s Disease, it is becoming more commonly accepted this buildup of protein is a byproduct of other pathophysiology, which is causing memory loss. However, these values may be a good indicator that Alzheimer’s Disease is present. Insurance is not typically covering this particular lab work at this time, but clinical research trials are a good way to get this information.
Symptomatically, Alzheimer’s Disease is rated on a scale that ranges from none to severe. The scale includes ratings of none, questionable, mild, moderate, and severe. Patients are rated on six domains, including memory, orientation, judgment & problem solving, community affairs, home and hobbies, and personal care. To obtain accurate scores for these domains, semi-structured interviews must be conducted by trained clinicians on both the patient and the patient’s caregiver. Then, interviews are translated to subscores and an overall score is calculated by the National Alzheimer’s Coordinating Center (2023). To see descriptions of the six domains at each level of functioning, you can view the Clinical Dementia Rating scoring table here https://knightadrc.wustl.edu/wp-content/uploads/2021/06/CDR-Table.pdf.
Individuals with a family history of Alzheimer’s Disease may be curious about genetic testing. It is important to keep in mind dilemmas may arise from this information such as, what will you do with this information? Who will you tell? Access to this information may be more harmful, so individuals are advised to proceed with caution. For individuals experiencing symptoms of Alzheimer’s Disease, genetic testing may be done through clinical research trials. Some clinics are able to complete genetic testing, but the cost is not covered by insurance at this time. Genetic testing relevant to Alzheimer’s Disease examines the Apolipoprotein E (APOE), a plasma protein on chromosome 19. APO has three common alleles: e2, e3, e4. One APOE allele is inherited from each parent. Presence of one copy of the e4 allele is associated with an increased risk of Alzheimer’s Disease and presence of two copies of the e4 allele is associated with an even higher risk of Alzheimer’s Disease. The e4 allele is a well-established risk factor, yet neither necessary nor sufficient to cause or diagnose Alzheimer’s Disease. APOE is also relevant for other health conditions and additionally, e4 as a modest risk factor for heart disease (University of Michigan, 2023). Additional information about genetic testing may be accessed here https://www.alz.org/media/Documents/genetic-testing-statement.pdf.