Alzheimer’s disease (AD) is a progressive, fatal brain disease. In the United States 5.3 million individuals suffer from Alzheimer’s disease. With the aging of the population and without successful treatment, AD will rise to affect 14 million American’s and 100 million people worldwide by 2050.
While increasing age is the largest risk factor for developing Alzheimer’s disease, severe memory loss is not a normal part of aging. Alzheimer’s disease is the most common form of dementia among older people.
Alzheimer’s disease affects the areas of the brain that are essential for thinking, memory and behavior. Symptoms of the disease include:
- Memory loss
- Misplaced things
- Changes in personality and behavior
- Poor judgment
- Problems with language
- Impaired visuospatial skills – difficulty perceiving spatial relationships or finding one's way
AD is caused by the abnormal accumulation of proteins in the brain -- amyloid protein, tau protein – leading to cell death. Risk factors for AD include:
- Age and family history
- Certain genes
- High blood pressure
- High cholesterol
Protection factors include:
- Mental activity
- Physical activity
- Healthy diet with antioxidants
- Mediterranean diet
How common is Alzheimer’s disease?
One in 10 people over age 65 and nearly half of people over 85 have Alzheimer’s disease. AD can affect people in their 40s. The percentage of people who have the disease increases every decade after the age of 60.
Other causes of dementia
Alzheimer’s disease is the most common cause of dementia, accounting for 60-70% of cases. Other causes of dementia include:
Tests commonly used to diagnose Alzheimer’s or to exclude other medical conditions include:
- Mental status test -- questions/tests to evaluate the amount of decline in mental functioning, including orientation, memory and language skills
- Neuropsychological testing
- Magnetic resonance (MR) scan of the brain
- Blood tests – blood counts, vitamin levels, liver and kidney function, mineral balance, thyroid gland function
- Positron emission tomography (PET) metabolic or amyloid scanning in some patients
Brain imaging helps to diagnose and understand Alzheimer’s disease
- Magnetic resonance imaging (MRI) can show brain shrinkage (atrophy)
- Decreased brain metabolism on FDG PET scans
- Increased brain amyloid on amyloid PET scans
Stages of Alzheimer’s disease
- No symptoms with Alzheimer’s present in the brain
- Mild symptoms with Alzheimer’s changes in the brain. Called prodromal AD, this is the phase of AD before Alzheimer’s dementia.
- Alzheimer’s dementia (mild) where daily function is beginning to be impaired.
- Alzheimer’s dementia (moderate) exhibits more severe impairment of memory and thinking. Behavioral changes are common in this stage.
- Alzheimer’s dementia (severe) is associated with very severe impairment. People in this stage often have difficulty walking and experience incontinence.
Brain changes in Alzheimer’s disease
Key changes in the brain in Alzheimer’s disease include:
- Brain shrinkage (atrophy)
- Loss of nerve cells
- Neuritic amyloid plaques
- Neurofibrillary tangles
- Brain inflammation
These three images show a routine T1-weighted MRI sequence from a normal subject. Within the brain, the white matter appears slightly brighter than the grey matter, or cortex. Regions containing cerebrospinal fluid (CSF) appear darker.
The top three images also show a routine T1-weighted MRI sequence, but from a patient with advanced Alzheimer's disease. In striking contrast to the normal subject, there is prominence of the CSF spaces both outside the brain (for example all the sulci are prominent) and within the ventricles. This increase is all caused by volume loss of the brain's white matter and grey matter.
The bottom 8 images are from an FDG-PET examination, which measures the brains metabolism. Using the colorized "heat" scale, where red shows the brain's normal high metabolism, and green-blue shows abnormally low metabolism, you can see a typical pattern of reduced metabolism in the bilateral parietal lobes, compatible with mid-stage Alzheimer's disease.
The medicines used to treat Alzheimer’s disease include the cholinesterase inhibitors (donepezil, rivastigmine, and galantamine), and the NMDA antagonist, memantine.
- Donepezil, rivastigmine, and galantamine work by slowing the breakdown of acetylcholine, the chemical that helps nerves communicate. They do not cure Alzheimer’s or stop the progression of the disease; they help relieve some memory impairment and reduce some behavioral symptoms. The most common side effects of the drugs are nausea, vomiting, and diarrhea. In some people, loss of appetite, insomnia or bad dreams, weakness, or fainting occur.
- Memantine blocks a brain receptor that is thought to enhance the cellular injury associated with Alzheimer’s disease. Side effects include somnolence (drowsiness), headache and dizziness.
- Patients can help develop new and better treatments for AD by participating in clinical trials. Cleveland Clinic Lou Ruvo Center for Brain Health is conducting several trials of promising drugs.
Alzheimer’s disease gets worse over time and is ultimately fatal. The course of the disease varies from person to person.
What research is being done on Alzheimer’s disease?
Researchers continue to study medications to treat Alzheimer’s disease. Carefully designed and conducted clinical trials are necessary to give a clear picture of safety and effectiveness before any approval might be considered.