Alzheimer’s disease is the most shared cause of dementia. It is a biological process that begins with the formation of protein buildups called amyloid plaques and neurofibrillary tangles in the brain. Over time, this leads to the death and shrinkage of brain cells. In the United States, approximately 6.9 million people over the age of 65 have Alzheimer’s disease. Of these, more than 70% are 75 years of age or older. Of the more than 55 million people with dementia worldwide, an estimated 60% to 70% have Alzheimer’s disease. Early symptoms of Alzheimer’s disease include forgetting recent events or conversations. Over time, Alzheimer’s disease causes severe memory loss and affects a person’s ability to perform everyday tasks.
Symptoms
Memory loss is a key symptom of Alzheimer’s disease. In the early stages of the disease, people may have difficulty remembering recent events or conversations. Over time, memory deteriorates, and other symptoms appear.
At first, a person with the disease may notice difficulty remembering and thinking clearly. As signs and symptoms worsen, family members or friends are more likely to see these problems.
Brain changes in Alzheimer’s disease cause the following symptoms, which worsen over time.
Memory
We all experience memory problems from time to time, but the memory loss associated with Alzheimer’s disease is lifelong. Over time, memory loss affects the ability to function at work and home.
People with Alzheimer’s may:
- Repeat the same statements and questions over and over;
- Forget conversations, appointments, or events;
- Lose objects, often placing them in places they don’t understand;
- Get lost in places they used to know well;
- Forget the names of family members and everyday objects;
- Have difficulty finding words, expressing thoughts, or holding conversations.
Thinking and Reasoning
Alzheimer’s disease causes difficulty concentrating and thinking, especially with abstract concepts like numbers. Multitasking is complicated. People with Alzheimer’s may also have difficulty managing finances, keeping track, and paying bills on time. Over time, they may lose the ability to recognise numbers.
Judgment and Decision-Making
Alzheimer’s disease makes it challenging to make good decisions and judgments. People with Alzheimer’s may make poor choices in social situations or wear inappropriate clothing for the weather. Everyday problems can be challenging to solve. A person with Alzheimer’s may not know how to handle burnt food on the stove or how to make decisions while driving.
Planning and Performing Routine Tasks
Routine activities that require completing steps in a specific order can also be strenuous for people with Alzheimer’s. They may have difficulty planning and making meals or playing a favourite game. As Alzheimer’s disease progresses, people forget how to do simple things like dressing and bathing.
Personality and Behaviour Changes
Brain changes that occur in Alzheimer’s disease can affect mood and behaviour. Symptoms may include:
- Loss of interest in activities.
- Social withdrawal.
- Mood swings.
- Distrust of others.
- Anger or aggression.
- Changes in sleep patterns.
- Mind wandering.
- Loss of self-control.
- Delusions include believing someone has stolen something when they haven’t.
Skill Retention
Despite significant changes in memory and skills, people with Alzheimer’s may retain some skills even when symptoms worsen. These skills are called retained skills. They include reading or listening to books, telling stories, sharing memories, singing, music, dancing, drawing, or doing crafts.
Retained skills may last longer because they are controlled by parts of the brain that are affected in later stages of the disease.
Causes
The exact causes of Alzheimer’s disease are not fully understood. But, essentially, brain proteins don’t function properly. This disrupts brain cells, also known as neurons, and triggers a series of events. Neurons become damaged and lose their connection to each other. Eventually, they die.
Scientists believe that most people with Alzheimer’s develop Alzheimer’s due to a combination of genetic, lifestyle, and environmental factors that affect the brain over time. In less than 1% of people, Alzheimer’s disease is due to specific genetic changes that virtually guarantee its development. In this group, the disease usually begins in middle age.
- The disease begins several years before the first symptoms appear. Most often, damage starts in the area of the brain responsible for memory. Neuron loss spreads fairly predictably to other regions of the brain. As the disease progresses, the brain decreases in size.
- Researchers trying to understand the cause of Alzheimer’s disease have focused on the function of two proteins:
- Beta-amyloid is a fragment of a larger protein. When these fragments stick together, they disrupt communication between brain cells. These accumulations form larger deposits called amyloid plaques.
- Tau proteins play a role in the brain cells’ internal support and transport system, transporting nutrients and other essential substances. In Alzheimer’s disease, tau proteins change shape and form neurofibrillary tangles. These tangles disrupt the transport system and cause cell damage.
Risk Factors
Risk factors for developing Alzheimer’s include age, family history, lifestyle, and other factors.
Advanced Age
Advanced age is the most important known risk factor for developing Alzheimer’s disease. Alzheimer’s disease is not part of typical ageing. However, the risk of developing it increases with age.
A study found that four new cases are diagnosed yearly for every 1,000 people between the ages of 65 and 74. Among people aged 75 to 84, 32 new cases are diagnosed per 1,000. After age 85, 76 new cases are diagnosed per 1,000.
Family History and Genetics
The risk of developing Alzheimer’s disease is higher if a first-degree relative, such as a parent or sibling, has been diagnosed with the disease. The influence of familial genes on risk is not fully understood. Genetic factors are likely complex.
A better-understood genetic factor is the shape of the apolipoprotein E (APOE) gene. Having a form of the gene known as APOE e4 increases the risk of developing Alzheimer’s. Between 25% and 30% of the population carries APOE e4. However, not all carriers of this form of the gene develop the disease. Having two copies of APOE e4 increases the risk of developing Alzheimer’s more than having a single copy.
Scientists have discovered rare changes in three genes that virtually guarantee that a person inheriting one will develop Alzheimer’s. However, these changes occur in less than 1% of people with Alzheimer’s.
Down Syndrome
Many people with Down syndrome develop Alzheimer’s. This is likely due to having three copies of chromosome 21. Chromosome 21 is the gene involved in producing a protein that leads to beta-amyloid formation. Fragments of beta-amyloid can form plaques in the brain. People with Down syndrome tend to develop symptoms 10 to 20 years earlier than the overall population.
Sex assigned at birth.
In general, women are more likely to develop this condition because they live longer than men.
Mild cognitive impairment
People with mild cognitive impairment (MCI) experience greater decline in recall or other thinking skills than is typical for their age. However, this decline does not interfere with the person’s ability to function at work or in their social life.
However, people with MCI have a higher risk of developing dementia than people without mild cognitive impairment. When MCI primarily affects memory, the disease is more likely to progress to dementia due to Alzheimer’s disease. A diagnosis of MCI gives people the opportunity to focus on healthy lifestyle changes and develop strategies to compensate for memory loss. They can also see their doctor regularly to monitor their symptoms.
Traumatic Brain Injury
Several large-scale studies have shown that people aged 50 and older who have suffered a traumatic brain injury (TBI) have an increased risk of developing dementia and Alzheimer’s disease. The risk is even higher in people with severe or multiple head injuries.
Air Pollution
Animal studies have shown that air pollutants can accelerate the deterioration of the nervous system. Human studies have shown that exposure to air pollution, especially from exhaust fumes and wood burning, is associated with an increased risk of dementia.
Alcohol Abuse
Excessive alcohol consumption has long been known to cause changes in the brain. Several large-scale studies and reviews have shown that excessive alcohol consumption is associated with an increased risk of dementia, especially early-onset dementia.
Sleep Disorders
Research has shown that sleep disorders, such as difficulty falling or staying asleep, are associated with an increased risk of Alzheimer’s disease. Sleep apnea may also increase the risk of dementia.
Overview
There is no cure for Alzheimer’s disease. In the more advanced stages, loss of brain function can lead to dehydration, poor nutrition, or infections. These complications can be fatal. However, medications can relieve symptoms or slow cognitive decline. Some programs and services can help people with the disease and their caregivers.