Alzheimer’s and Parkinson’s Disease: What’s the Connection?

Parkinson's disease and Alzheimer's disease are both neurological conditions caused by neurodegeneration (gradual damage to brain cells).

Like other progressive brain diseases, they are associated with a buildup of certain proteins in the brain. Each of these conditions has its own set of symptoms and a specific type of protein accumulation in certain locations of the brain.

While it's not common, it's possible to have both diseases at the same time. Alzheimer's disease always causes dementia; Parkinson's disease, a movement disorder, can sometimes cause dementia. This article describes the different and similar cognitive (thinking ability) and behavioral changes of Alzheimer's and Parkinson's.

Parkinson’s Disease: Symptoms, Stages, and Treatment

Parkinson's disease usually begins after age 60, gradually progressing over the years. Some people can have early-onset Parkinson's disease, starting in their 30s or 40s. It is primarily a movement disorder characterized by resting tremors and slowness and stiffness of movement.

In the late stages of the disease, Parkinson's dementia can develop. But most people who have Parkinson's disease do not develop dementia as a part of the condition.

Parkinson’s Disease Symptoms

Sometimes the symptoms of Parkinson's disease fluctuate over the course of the day, with an overall decline that is noticeable over time. In its late stages, the condition can limit mobility and self-care.

The most common symptoms include:

• Tremors while at rest, usually of the arms, legs, or jaw
• Slow, shuffling way of walking
• Trouble with balance
• Quiet, rapid speech, with minimal mouth movement
• Stiff arm and leg movements
• Expressionless face
• Dry skin
• Diminished emotions or very emotional expressions (such as frequent crying)
• Depression
• Constipation
• Cognitive impairment
• Dementia
• Hallucinations

You can experience several of these symptoms in the early stages, and you may eventually experience all of them in the late stages.

Side effects of Parkinson's medications can include hallucinations and dyskinesia, which are movement problems that are different than the movement problems caused by Parkinson's disease.

Parkinson’s Disease Stages

There are well-defined stages of Parkinson’s disease.

The stages are defined as:

• Stage 1: Mild symptoms, typically affecting one side of the body
• Stage 2: Worsening symptoms, affecting both sides of the body; daily tasks can be slow or difficult.
• Stage 3: Symptoms can interfere with daily life; falling may occur.
• Stage 4: Severe symptoms, requiring a walker or other assistance to stand and walk
• Stage 5: Unable to walk, relies on a wheelchair, or may be bedbound; cognitive effects can be substantial.

Most people with Parkinson’s disease will progress through these stages, but sometimes progression can vary, and you might remain in an early stage for many years.

Parkinson’s Disease Treatment

Many effective treatments can control symptoms of Parkinson’s disease, even at late stages. There are no treatments proven to prevent progression, but early treatment might slow progression for some people.

Common treatments include:

• Parkinson’s medications: These medications affect neurotransmitter (chemicals in the brain) activity to reduce the symptoms of Parkinson’s disease.
• Symptomatic treatments: These medications do not specifically treat Parkinson’s disease, but they may control some symptoms. For example, your doctor might prescribe treatment for constipation or depression.
• Deep brain stimulation: This is a type of Parkinson’s disease surgery in which a device is implanted in the brain to create electrical signals that help control the movement symptoms. It can be effective for some people, and you might be able to reduce the dose of medication you take for Parkinson’s disease treatment.
• Occupational and physical therapy: You might benefit from working with a therapist to gain better control over your body movements so you can avoid falls and do the things you need and want to do.

Alzheimer’s Disease: Symptoms, Stages, and Treatment

Alzheimer’s disease is a condition characterized by impairment of memory, thinking, behavior, and self-care. It often begins after age 70, but it can start sooner. Alzheimer’s disease is not associated with symptoms that affect physical movement.

Alzheimer’s Symptoms

The effects of Alzheimer’s disease worsen over time. Sometimes the symptoms can be more noticeable when a person is tired or has another illness, such as an infection, kidney disease, or liver disease.

Common symptoms of Alzheimer’s disease are:

• Difficulty remembering things
• Trouble concentrating
• Difficulty with problem solving
• Getting lost
• Changes in appetite
• Paranoia and mistrust of others
• Excessive sleeping
• Agitation
• Lack of attention to self-care
• Depression

Sometimes these symptoms are associated with each other. For example, forgetting where something is located can make people think it was stolen, worsening paranoia.

Stages of Alzheimer’s

There are several ways that stages of Alzheimer’s disease are defined, and they can progress quickly or slowly. Sometimes progression can seem to slow down, and then the disease can rapidly worsen.

The seven stages of Alzheimer’s disease are:

• Stage 1: Before symptoms begin
• Stage 2: Mild forgetfulness
• Stage 3: Increasingly significant forgetfulness
• Stage 4: Forgetfulness and difficulty with decision making
• Stage 5: Severely impaired self-care and interactions with
  others
• Stage 6: Personality changes and lack of independence
• Stage 7: Inability to eat, lack of mobility

People who have advanced Alzheimer’s disease can become very passive, often losing interest in eating. Nutrition, bedsores, and infections can become serious problems. During the advanced stages, agitation can also be a problem, and people may resist medical care, including actions such as pulling out intravenous lines or feeding tubes.

Alzheimer’s Treatment

There are several medical treatments that can be prescribed for Alzheimer’s disease. They may help slow down progression of the disease for some people, but they do not treat symptoms or reverse any effects of the disease.

Medications approved for treating Alzheimer’s disease include:

• Namenda (memantine)
• Aricept (donepezil)
• Razadyne (galantamine)
• Exelon (rivastigmine)
• Leqembi (lecanemab)

Additionally, symptomatic treatments may be prescribed to alleviate some effects of the disease, such as depression or agitation.

Alzheimer’s vs. Parkinson's Disease Dementia

The dementia of Parkinson’s disease has some similarities to the dementia of Alzheimer’s disease. And there are some differences, too. Alzheimer’s disease causes dementia slowly over time, while the dementia of Parkinson’s disease often develops more quickly and dramatically.

The symptoms of Parkinson’s dementia can come and go from day to day, while the symptoms of Alzheimer’s dementia will not go away.

The hallucinations that can occur with Parkinson’s disease are usually caused by the medications used to treat the condition.

Another condition, Lewy body disease, often described as Parkinson plus or parkinsonism, is characterized by some of the movement problems that can occur with Parkinson’s disease, along with severe and progressive dementia and hallucinations.

Associated brain changes differ for each condition:

• Alzheimer’s dementia is associated with changes in the brain, including a buildup of amyloid beta plaques and neurofibrillary tangles in the brain. There is also degeneration of the hippocampus, an area of the brain associated with memory.
• Parkinson’s disease is associated with degeneration of the basal ganglia and a buildup of Lewy body proteins in the brain. Parkinson’s dementia is also associated with additional degeneration of the thalamus and the hippocampus.

These conditions can cause changes on imaging studies, but they don’t always do so. The protein accumulation may be identified based on research studies and autopsy examination and sometimes with functional brain imaging.

The protein accumulation and brain degeneration are not diagnostic—these findings are used in research studies that examine ways to treat or prevent Alzheimer’s disease and Parkinson’s disease.

Coping With Alzheimer’s and Parkinson’s Disease

Living with both Alzheimer’s disease and Parkinson’s disease is extremely challenging. The dementia of Alzheimer’s combined with the movement effects of Parkinson’s (and possibly Parkinson’s dementia) can make self-care especially difficult.

Rivastigmine is the only medication that is specifically approved for the treatment of Parkinson’s dementia. Additionally, you may need medication for the motor symptoms of Parkinson’s disease (those related to movement) and medication to help with other symptoms, such as dry skin.

Lifestyle Changes

Other strategies proven to help people with both Alzheimer’s and Parkinson’s disease include:

• Social engagement
• Mental stimulation
• Regular exercise
• Healthy diet
• Quality sleep
• Attention to vascular health
• Stress management

The burden on loved ones can seem overwhelming. Between providing constant care and worrying about your loved one becoming injured or getting lost, you will need to seek professional support to help you take care of your loved one—and get some rest and self-care for yourself.

Consider reaching out to a therapist and/or a support group so you can express your feelings and learn ways to cope.

Summary

Parkinson's disease and Alzheimer's disease are progressive brain diseases caused by gradual damage to brain cells. Each of these conditions has its own set of symptoms, stages, and treatments. Dementia is always seen in Alzheimer's disease. Parkinson's disease is a movement disorder that can lead to dementia. It's possible to have both diseases at the same time.

A Word From Verywell

Parkinson’s disease and Alzheimer’s disease are each not uncommon, and they occur with advanced age. It can be extremely stressful to learn that you or a loved one has one or both conditions.

The memory and behavioral changes can often be confusing—you might not know whether symptoms are caused by the disease, medication side effects, or another problem (like an infection).

If you or a loved one has been diagnosed with Parkinson’s disease or Alzheimer’s disease, it’s important that you use all the resources available to you—social work, home health, physical therapy, occupational therapy, nutritionist—to have the best quality of life possible.