Everyone ages, and as we do, we experience decreased speed of thought and difficulty remembering certain details. In some people, however, this cognitive decline is much more rapid in its pace and more pronounced in its affects, leading to a condition called dementia. In a large number of dementia cases, the sufferer is afflicted by a specific form called Alzheimer’s disease. People suffering from this disease experience severe declines in cognitive ability which produces adverse effects on their memory and behavior.
What Causes Alzheimer’s Disease?
The brain is composed of billions upon billions of cells called neurons. Working in concert through electro-chemical reactions, neurons are responsible for all aspects of human cognition and activity, from speech to learning to action. As with all cells and organs, the effective functioning of neurons in the brain decreases as we age, leading to problems with memory and changes in our behavior.Alzheimer’s disease is characterized by particularly debilitating degeneration and death of neurons. The typical mental symptoms of aging occur much more quickly and with greater intensity in Alzheimer’s patients. While the exact causes are still unknown, there are consistent mechanisms by which Alzheimer’s develops and progresses, spreading outward from the initial site into adjacent areas of the brain. Two characteristic, abnormal structures develop in the brain, in and amongst the constituent neurons. These are called plaques and tangles. Plaques are buildups of protein fragments called beta-amyloids. Plaques aggregate in the gaps between neurons, called synapses, inhibit the chemical communication between neurons. Tangles, on the other hand, are twisted fibers of tau protein inside of individual neurons, damaging their integrity and disrupting electrical function. Plaques and tangles develop over the course of most people’s lives, but the plaques and tangles associated with Alzheimer’s disease are more extensive and crippling.Medical scientists are still unsure of how, exactly, plaques and tangles cause the characteristic symptoms of Alzheimer’s disease. They have, however, confirmed that these abnormal structures develop far more extensively and in characteristic patterns in the brains of people afflicted with Alzheimer’s disease. Plaques hinder communication amongst neurons, ultimately blocking certain important paths. Tangles disrupt the internal processes by which neurons maintain themselves and perform their functions. These effects eventually lead to decreased brain size and function.
At this stage, a person afflicted with Alzheimer’s disease will show no symptoms; their memory will be unimpaired and their behavior will carry on characteristically. However, during this stage, the beta-amyloid and tau proteins discussed above are building up and aggregating in and amongst the still-healthy neurons. This development and progression can be seen with brain imaging techniques. However, since these toxic structures are not yet pervasive enough to inflict debilitating damage, a person at the preclinical stage of Alzheimer’s disease shows no noticeable cognitive or behavioral impairment.
The initial damage of Alzheimer’s disease occurs in an area of the brain called the hippocampus. This is a structure of neurons that performs an essential role in the formation of new memories. The damage that plaques and tangles wreak in the hippocampus leads directly to early difficulty remember recently learned information.This condition is called mild cognitive impairment. It entails greater difficulty thinking and remembering things than is normal for people of a given age, but not to an extent that it interferes with daily activities or their quality of life. As a result, these early symptoms of Alzheimer’s disease make it difficult, if not impossible, for sufferers to recognize that they are experiencing cognitive issues. Those issues, however, will likely be more evident to the people around them, such as friends, family and coworkers.
From the hippocampus, plaques and tangles spread outward, affecting more and ever-larger portions of the brain. This progression leads to disorientation and loss of motor functions.The most recognizable symptoms of late-stage Alzheimer’s disease are severe memory loss and confusion regarding time, location, and events. These symptoms are concurrent with changes in the afflicted patient’s disposition and behavior. This may manifest as delusions, hallucinations and even paranoid suspicions about the people in their everyday lives, including friends, family and caregivers.Ultimately, Alzheimer’s disease pervades the brain and affects all aspects of mental and physical life. This leads to an inability to perform even the most basic of activities, like speaking, eating and walking. In the end, the brain is too impaired to maintain the basic functions of life.If you suspect symptoms of Alzheimer’s disease in yourself or a loved one, it is important that you or they visit a doctor as soon as possible. Although medical understanding of Alzheimer’s disease is far from complete, professionals are now able to diagnose the disease and implement treatment at an early stage. While Alzheimer’s disease is incurable and ultimately fatal, it is nonetheless possible to extend a patient’s life for as much as a decade if action is taken before the disease progresses too far.