Parkinson’s and Alzheimer’s are disorders of the brain. Damage to the brain affects how the nerve cells work, leading to movement, cognition, and behavior changes.
Parkinson’s disease is a neurodegenerative disorder of the brain. Symptoms of Parkinson’s usually appear gradually and progress over time.
The National Institute on Aging (NIA) notes that Parkinson’s affects dopamine-producing nerve cells in a part of the brain called the substantia nigra. Death or impairment of nerve cells leads to a decrease in dopamine production which affects movement.
Parkinson’s may also affect other neurotransmitters that regulate functions such as blood pressure, digestion, and sweating.
A loss of nerve endings decreases norepinephrine, which can lead to symptoms of Parkinson’s, including fatigue and changes in blood pressure.
In Alzheimer’s, a type of protein called beta-amyloid builds up between nerve cells in the brain to form plaques.
A protein called tau also builds up and forms threads that tangle up inside of nerve cells. These neurofibrillary tangles impair the way nerve cells communicate with each other.
Healthy nerve cells lose their connection to other nerve cells and stop functioning properly or die.
Brain damage in Alzheimer’s begins in the hippocampus and the entorhinal cortex, which are the areas of the brain involved in creating memories. As Alzheimer’s progresses, damage can affect more brain areas, and sometimes brain atrophy, or shrinking of the brain, can occur.
Although Parkinson’s and Alzheimer’s share some similar symptoms and risk factors, there does not appear to be a link between Parkinson’s and Alzheimer’s, nor any evidence that one can lead to the other.
People may find it difficult to tell the difference when they or a family member begin to develop the first signs of Parkinson’s disease or Alzheimer’s disease.
Early on, both conditions can cause people to feel as if they are not themselves and become less sharp in their thinking and less quick in their movements.
|Parkinson’s disease||Alzheimer’s disease|
• body stiffness
• slow movement
• impaired balance and coordination
• difficulty swallowing and chewing
• difficulty speaking
• urinary problems
• sleep disruptions
|• memory problems
• difficulty carrying out everyday tasks
• difficulty finding words
|Age of onset||The average age of onset is typically 60 years.
Rarely, it appears before the age of 40.
|Most cases are late-onset, with symptoms beginning at around 65 years.
Early-onset is less common and can occur before the age of 65.
|Causes||A combination of genetic and environmental factors can contribute to Parkinson’s.||A combination of genetic, lifestyle, and environmental factors can contribute to Alzheimer’s.|
|Risk factors||• older age
• exposure to toxins
• head injury
• being male
|• older age
• family history
• head injury
• cardiovascular conditions
• deep brain stimulation
• physical therapy
• physical activity
• dietary changes
• cognitive and behavioral therapy
|Life expectancy||Parkinson’s does not reduce a person’s life expectancy, but it can cause people to become more vulnerable to infections or falls.||Following a diagnosis, the average life expectancy is 4–8 years, but some people may live up to 20 years.|
|Outlook||As Parkinson’s progresses, symptoms may worsen.||It is a progressive disease, so symptoms may worsen over time.|
People with Parkinson’s and Alzheimer’s disease may experience the following symptoms:
Symptoms of Parkinson’s develop gradually over time. The rate of progression varies between individuals.
The main symptoms affect movement:
- a tremor in the hands, arms, legs, jaw, or head
- stiffness of the limbs and upper body
- decreased facial expression
- slowed movement
- reduced balance and coordination, which may lead to falls
Other symptoms can be non-movement related, such as:
- problems with swallowing, chewing, or speaking
- urinary problems
- skin issues
- disrupted sleep
Parkinson’s can affect anyone, but it affects roughly 50% more males than females.
The first symptoms of Alzheimer’s can include:
- memory problems
- difficulty finding words
- issues with vision and spatial awareness
- impaired reasoning or judgment
- getting lost easily
- taking longer to carry out everyday tasks
- difficulty handling money or paying bills
- repeating questions
- changes in behavior or personality
As the disease progresses, people may develop the following symptoms:
- unable to correctly identify smells or sounds
- worsening memory loss and confusion
- difficulty recognizing familiar faces, such as family and friends
- unable to learn new things or cope with new situations
- unable to carry out everyday tasks that involve multiple steps, such as getting dressed
- delusions or paranoia
- impulsive behavior
In severe Alzheimer’s, a person may lack the ability to communicate and be dependent on caregivers.
Age of onset and progression
The age of onset and how the condition progresses varies between the two diseases.
Parkinson’s can begin earlier than Alzheimer’s, usually at around 60 years.
Around 5–10% of people will develop early-onset Parkinson’s before the age of 50.
The progression of Parkinson’s can vary between individuals. Parkinson’s symptoms tend to develop gradually and worsen over time. People may find it more difficult to walk or talk as usual as Parkinson’s progresses.
In most cases, people with Alzheimer’s first develop symptoms at about 65 years old.
When people develop symptoms before the age of 60, healthcare professionals refer to this as early-onset Alzheimer’s. This is less common.
According to the NIA the following stages mark the progression of Alzheimer’s:
- Mild: People who have cognitive difficulties may receive a diagnosis at this stage.
- Moderate: The disease affects memory, reasoning, and sensory processing.
- Severe: The brain tissue can shrink, and people might stop eating.
Causes and risk factors
The following are causes and risk factors for Parkinson’s and Alzheimer’s.
According to the NIA, Parkinson’s may be hereditary in some cases. It may occur due to genetic mutations. Typically, however, Parkinson’s occurs randomly.
Parkinson’s may develop due to genetic and environmental factors, including exposure to toxins or a head injury.
Risk factors for Parkinson’s include:
- traumatic brain injury
- area of residence, which may be due to environmental factors or genetics
- exposure to certain metals, although researchers need further evidence
- exposure to solvents, such as trichloroethylene (TCE) and polychlorinated biphenyls (PCBs)
- exposure to pesticides and herbicides, such as paraquat
- being over the age of 60
Parkinson’s more commonly affects males than females.
Early-onset Alzheimer’s may be due to a genetic mutation.
Risk factors for Alzheimer’s include:
- older age
- a family history of Alzheimer’s
- traumatic brain injury
- cardiovascular conditions, such as heart disease, diabetes, stroke, high blood pressure, or high cholesterol.
According to the Alzheimer’s Association, African American’s are approximately twice as likely to have Alzheimer’s and other types of dementia than white Americans.
Hispanic people are one and a half times more likely than white people to have Alzheimer’s or another form of dementia.
However, African Americans and Hispanic people are less likely to receive a diagnosis, and the diagnosis typically occurs when dementia has reached the later stages.
Suspected risk factors for Alzheimer’s, such as high blood pressure and diabetes, are more prevalent in the African American and Hispanic communities.
Treatment options for each condition include:
Certain medications can help to increase dopamine levels, affect brain chemicals, and help relieve non-motor symptoms.
A common medication for Parkinson’s is levodopa, or L-dopa, which helps to replace dopamine levels. People may take another drug called carbidopa at the same time to help reduce side effects. There are many other medications as well.
Many people have physical or occupational therapy, see a nutritionist or dietitian for dietary advice, or do exercises to increase muscle strength and balance.
If medication is not effective, deep brain stimulation (DBS) may help relieve movement-related symptoms. However, this is not a common form of treatment.
DBS involves a surgeon implanting electrodes into the brain, which connect to an electrical device in the chest. DBS stimulates the brain and helps relieve symptoms, such as tremors and loss of movement.
Treatment for Alzheimer’s may help to slow disease progression and relieve symptoms.
A healthcare professional may prescribe donepezil, rivastigmine, and galantamine to help regulate neurotransmitters. A medication called aducanumab may help reduce amyloid buildup in the brain and slow disease progression.
People may also undergo other treatments, such as physical activity, dietary changes, and cognitive and behavioral therapy.
Life expectancy and outlook
Alzheimer’s and Parkinson’s are progressive neurodegenerative conditions, which will worsen over time.
There is currently no cure for Parkinson’s, but treatment can help relieve symptoms and improve quality of life.
Although Parkinson’s is not fatal, it can cause life threatening complications. According to a 2021 study, people with Parkinson’s have an increased risk of aspiration pneumonia, which is responsible for 70% of deaths in people with Parkinson’s.
Alzheimer’s is a progressive disease, which means the symptoms worsen over time.
The average life expectancy for a person with Alzheimer’s is 4–8 years following a diagnosis, but some people may live up to 20 years. Life expectancy can depend on a range of factors, such as overall health.
It is not possible to prevent Parkinson’s or Alzheimer’s disease. However, a person can take steps to reduce the risk of developing the diseases.
A person can try the following to help prevent Parkinson’s disease:
- doing exercise
- eating foods containing vitamin D
- eating foods containing niacin, which is a form of vitamin B
However, more research is necessary to confirm these findings, so people should not consume caffeine and uric acid as prevention strategies.
A person should talk to a medical professional before increasing their caffeine or uric acid intake.
Taking steps to promote healthy aging may reduce the risk of Alzheimer’s, such as:
- eating a healthy, balanced diet
- staying physically active
- keeping socially connected
- avoiding tobacco
- limiting alcohol
- keeping mentally stimulated
Diagnosing Parkinson’s and Alzheimer’s is not always straightforward and may involve a variety of diagnostic tools.
There is no set test to diagnose Parkinson’s, so a doctor may use a combination of methods, such as:
- examining symptoms and medical history
- carrying out a neurological examination
- reviewing a person’s response to Parkinson’s medications
To diagnose Alzheimer’s, a doctor may use a variety of methods, such as:
- asking about medical history, overall health, and any changes in behavior or personality
- performing tests on memory, problem-solving, counting, language use, and attention
- performing blood and urine tests to rule out other conditions
- ordering brain scans, such as CT or MRI scans, to rule out other conditions
Contacting a doctor
People will need to contact a doctor if they or a loved one has any signs of Parkinson’s or Alzheimer’s.
Prompt diagnosis and treatment may help to relieve symptoms and may slow any progression of brain damage.
Both Parkinson’s and Alzheimer’s are brain disorders that affect memory, movement, and communication.
Both conditions are progressive, which means symptoms may worsen over time. Treatment may help to relieve symptoms and slow down disease progression.