Overview
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder in which the brain shrinks and the cells of the central nervous system do not work and die. It worsens with time and cannot be cured or reversed. Over time, death is inevitable.
There is marked cognitive and behavioral dysfunction that considerably interferes with social and daily functions. It is a type of dementia that adversely affects memory, thinking, and behavior. Symptoms eventually become severe and interfere with daily tasks.
Alzheimer’s is a progressive disease in which plaques develop in the hippocampus, a center in the brain that helps to store memories. It also involves other areas of the cerebral cortex that control thinking and decision-making.
Whether plaques develop and cause Alzheimer’s or whether they develop because of AD remains unknown.
Alzheimer’s disease is the most common cause of dementia in which there is a progressive decline in brain function. The person starts losing his thinking, behavioral and social ability and begins to lose his capability to function independently and carry out his daily tasks.
The early signs of the disease include forgetting recent incidents but as the disease progresses, the person will develop severe memory loss and will not be able to carry out everyday activities.
Most people with Alzheimer’s are 65 years and older. Medications may improve or slow the progression of symptoms, but that is only temporary. They may help improve the declining functional ability and maintain the independence of the person for some time.
Different programs and services for such patients are available and they can help support the person but only temporarily.
There is no cure and in the advanced stages of the disease, complications develop in the form of severe brain function loss. Dehydration, malnutrition, or infection develop and result in death.
However, early, accurate diagnosis and treatment of Alzheimer’s disease are beneficial because they keep improving the quality of life of the patient for a longer period of time. This is because most medicines currently available are more effective for people in the early or middle stages of the disease.
Causes and pathophysiology
The exact causes of Alzheimer’s disease aren’t entirely understood. But, basically, the brain proteins do not function, which disrupts the working of the neurons (brain cells). The neurons are damaged and there is a loss of neurotransmission leading to the death of the nerve cells ultimately.
Research believes that in most cases, there is no single cause for AD. It is a combination of genetic, lifestyle, and environmental factors that collectively are responsible for its etiology.
The brain has 100 billion nerve cells (neurons). Each nerve cell connects with many others to form groups or networks that communicate with each other. These groups of neurons perform special tasks such as thinking, learning, and memorizing. Others help with special senses like seeing, hearing, and smell.
The causative process starts years before the first symptoms manifest. This progressive pathology most often starts in the area of the brain that controls memory.
Damage to the neurons is not localized and spreads in a fixed pattern to other regions of the brain. In the late stage of the disease, there is significant shrinkage of the brain.
The cause of Alzheimer’s disease is focused on the role of two proteins: plaques and tangles, which are prime suspects in damaging and killing nerve cells.
1. Plaques are deposits of a larger protein fragment called beta-amyloid that build up in the spaces between nerve cells and they appear to have a toxic effect on neurons.
2. Tangles are twisted fibers of another protein called tau that builds up inside cells. These proteins change shape and arrange themselves into structures called neurofibrillary tangles. The tangles disrupt the neurotransmission system and cause neuron toxicity.
Though many people develop some plaques and tangles as they age, those with Alzheimer’s develop them much more, beginning in the areas responsible for memory before spreading to other areas in the brain.
Experts believe plaques and tangles play a vital role in blocking neurotransmission and disrupting processes necessary for cellular survival.
It’s the damage and death of nerve cells that cause AD symptoms like memory loss, behavioral changes, and inability to perform daily tasks.
What deficiencies can cause Alzheimer’s disease?
“Levels of one neurotransmitter, acetylcholine, are particularly low in the brains of people with Alzheimer’s disease”.
“Vitamin D also plays an important role in neurodegenerative processes. Its deficiency is a genetic risk factor for AD, Parkinson’s disease, multiple sclerosis, and vascular dementia”.
“A deficiency of a protein called RbAp48 in the hippocampus appears to significantly contribute to the memory loss that creeps up on you as you age”.
“Elevated methylmalonic acid and serum homocysteine levels are specific markers of vitamin B12 deficiency and are also associated with poor myelination. Elevated homocysteine levels may be associated with Alzheimer’s disease”.
Risk factors
- Age. Advancing age is the greatest known risk factor for Alzheimer’s disease. This is seen by the fact that the majority of people with Alzheimer’s are 65 and older.
- Family history and genetics. Your risk of developing Alzheimer’s increases if a first-degree relative — your parent or sibling — has the disease. Most of these genetic mechanisms are unexplained and complex. However, a form of the apolipoprotein E gene (APOE), which is a variation of the gene, APOE e4, increases the risk of Alzheimer’s disease but not all people with genetic variation develop the disease. Scientists have identified mutations in three genes that are almost certain to cause AD in a person who inherits one of them. Still, these mutations account for less than 1% of people with Alzheimer’s disease.
- Down syndrome. Many people with Down syndrome develop Alzheimer’s disease. Down syndrome is a condition in which a person has an extra chromosome. Signs and symptoms tend to appear 10 to 20 years earlier in such people than they do in people without Down syndrome.
- Sex. There are more women living than men with AD possibly because they generally live longer than men. Otherwise, there appears to be little difference in risk between both sexes.
- Mild cognitive impairment (MCI). People who have MCI are at a higher risk of developing dementia. If memory is affected in these people, the condition is more likely to progress to dementia due to Alzheimer’s disease. Mild cognitive impairment is a decline in memory and thinking skills that is abnormal for a person’s age. However, the person with MCI is still able to do his work and move in social circles.
- Head trauma. Several studies have found that for people aged 50 years or more who had a history of traumatic brain injury (TBI), the risk of dementia and Alzheimer’s disease increased. The risk is at its greatest during the first six months to two years after the TBI.
- Air pollution. Air pollution can speed up the deterioration of the nervous system. Studies have found that air pollution exposure, especially that generated from traffic exhaust and burning wood increases your risk of dementia.
- Excessive alcohol consumption. It is long known that drinking too much alcohol causes changes in the brain. Several studies discovered that alcohol abuse was linked to an increased risk of dementia, which was likely to onset early.
- Poor sleep patterns. Chronically, having inadequate sleep is associated with a higher risk of Alzheimer’s disease. If you suffer from sleeplessness or have difficulty staying asleep, you are at a higher risk.
- Indisciplined lifestyle. Wrong lifestyle habits lead to health conditions and significantly increase your risk of AD. Reversing these trends can reverse your risk but only before AD sets in. These include:
- Sedentary lifestyle with little or no physical activity
- Obesity
- Smoking
- High blood pressure
- High cholesterol
- Poorly controlled diabetes
Complications
Cognitive changes caused by Alzheimer’s such as memory loss, inability to speak, and impaired judgment can cause hurdles in the treatment of other health conditions that may arise.
This is because of the patient’s inability to understand and communicate his symptoms of another illness, explain any side effects, and understand and forget what the doctor prescribed and advised.
As Alzheimer’s disease progresses to its last stages, that progressing brain changes gradually begin to show physical dysfunctions.
These could include physical functions, such as swallowing, balance, and bowel and bladder control. These dysfunctions increase the risk of additional health problems such as:
- Inhaling food or liquid into the lungs (aspiration) can cause aspiration pneumonia
- Febrile infections like the flu
- Falls leading to fractures are most likely due to osteoporosis, which is often seen in older people
- Bedsores due to prolonged periods of being bedridden
- Malnutrition
- Dehydration
- GI problems like constipation or diarrhea
- Dental problems such as mouth sores or tooth decay due to poor oral hygiene
Aspiration pneumonia is a common cause of death in people with Alzheimer’s because the inability to swallow leads the food and beverages to enter the lungs through the windpipe and cause infection in the lungs.
Other common causes of death among people with Alzheimer’s disease include dehydration, malnutrition, and other infections.
Signs and symptoms
Signs and symptoms vary and increase in severity as AD progresses
Symptoms of preclinical Alzheimer’s disease
The neuropathology of AD can begin many years before symptoms appear, as much as 30 years before dementia symptoms develop.
A patient with preclinical AD may apparently appear completely normal on clinical examination and mental status testing done to check a person’s thinking ability.
Neuroimaging is done to detect preclinical AD in which specific regions of the brain such as the entorhinal cortex and hippocampus are seen to be affected.
CSF fluid biomarkers seen in CSF obtained through a lumbar puncture will show the presence of multiple markers such as tau and beta-amyloid, two markers that form abnormal brain deposits strongly associated with Alzheimer’s.
These investigations can help diagnose preclinical Alzheimer’s even before the symptoms present.
Symptoms of mild Alzheimer’s disease
Signs of mild AD can include the following:
- Loss of memory
- Confusion about understanding anything
- Taking longer to do normal tasks
- Problems in handling money matters
- Error in judgment, which often leads to wrong decisions
- No initiative to do anything
- Mood and personality changes
Symptoms of moderate Alzheimer’s disease
The symptoms of this stage can include the following:
- Increasing memory loss and confusion
- Cannot recognize friends and family
- Difficulty in reading, writing, and speech
- Cannot think logically
- Cannot cope with new situations
- Restlessness, agitation, and anxiety
- Wandering
- Repeating statements
- Hallucinations, delusions, or paranoia
- Sensory and motor problems like for example, trouble getting out of a chair or setting the table
Symptoms of severe Alzheimer’s disease
Patients with severe AD are unable to recognize even family or loved ones and are not able to communicate properly.
They completely depend on others for everyday activities and care.
Common symptoms of severe AD can include:
- Loss of weight
- Seizures
- Difficulty swallowing
- Groaning often
- Increase in sleeping hours
- Loss of bladder and bowel control
- Towards the end stage, AD patients may spend most of their time in bed.
- Death often results due to other illnesses, such as aspiration pneumonia, which is most common.