Parkinson’s disease is a movement disorder, while Alzheimer’s disease affects cognition (memory and thinking). Although these two conditions are different, they do have some things in common. Knowing the similarities and differences can help you or your loved one get the right diagnosis and care.

Here’s what you need to know about how Parkinson’s and Alzheimer’s disease alike — and how they differ. This may help you talk to a healthcare provider about diagnosis, treatment, and more.

Similarities Between Parkinson’s and Alzheimer’s

There are a few ways that Parkinson’s and Alzheimer’s are similar. Knowing these can help you understand what you or a loved one may be experiencing, no matter which condition you or your family member is eventually diagnosed with.

1. Both Are Neurological Conditions

Both Parkinson’s disease and Alzheimer’s are neurological conditions. This means they involve parts of the brain and how they work. In Alzheimer’s disease, abnormal protein buildup around brain cells causes them to stop working. In Parkinson’s, brain cells that make a chemical called dopamine stop working properly and eventually die.

2. Both Get Worse Over Time

Alzheimer’s disease and Parkinson’s are both progressive, meaning they get worse over time. Parkinson’s usually starts with movement (or motor) symptoms. These symptoms start slowly and get worse gradually. Other symptoms may appear later on, too.

Alzheimer’s also starts off slowly and can progress over many years. Some people may live with it for more than 10 years. Most people progress through five stages over the course of the disease.

3. Both Include Symptoms of Dementia

Both conditions can cause dementia. Dementia involves cognitive (thinking-related) symptoms including problems with memory, thinking, or social skills that are serious enough to affect daily life. In Alzheimer’s disease, dementia is the main symptom.

In Parkinson’s, dementia isn’t always present, but it can be. About half of people with Parkinson’s have mild cognitive impairment, which are cognitive symptoms that don’t interfere with daily life. Some people with Parkinson’s disease develop dementia as the condition progresses.

4. Both Can Involve Delusions and/or Hallucinations

Parkinson’s and Alzheimer’s can both cause delusions and hallucinations. Delusions are false beliefs that aren’t based in reality, such as being paranoid or very suspicious. Hallucinations happen when a person sees or hears people or things that aren’t there.

In Parkinson’s disease, delusions and hallucinations may happen because of dementia. They may also happen as a side effect of some of the medications used to treat the condition.

In people living with Alzheimer’s, delusions and hallucinations (sometimes called Alzheimer’s psychosis) can also happen. Hallucinations with Alzheimer’s may be caused by changes in the brain due to the condition. They can also be triggered by illnesses or medications.

5. Both Require Significant Caregiving

As both Alzheimer’s and Parkinson’s affect the brain, they often require long-term care. When thinking or movement becomes difficult, a person may need help with daily tasks like getting dressed, eating, cooking, and moving around. Having good care can improve a person’s quality of life and help people with either diagnosis live as well as possible.

Differences Between Parkinson’s and Alzheimer’s

Even though Parkinson’s and Alzheimer’s disease share some symptoms, they are very different diseases. These differences help healthcare experts providers make the right diagnosis and create the best care plan for each person.

1. They Have Different Causes

One major difference between Alzheimer’s and Parkinson’s is what causes them. Alzheimer’s disease is linked to two proteins in the brain that don’t work the way they should. These are called beta-amyloid and tau proteins.

Parkinson’s is linked to a different protein called alpha-synuclein. This protein is connected to the destruction of cells that produce dopamine.

2. They Have Different Treatments

Because Parkinson’s disease and Alzheimer’s disease have different causes and symptoms, their treatments are also different. Most treatments for Parkinson’s focus on increasing dopamine, helping the brain use dopamine more effectively, or stopping dopamine from breaking down too quickly.

Treatments for Alzheimer’s, on the other hand, mostly help cells communicate better and aim to prevent additional proteins from working incorrectly.

In both conditions, doctors may also treat specific symptoms as they show up.

3. Dementia Onset Looks Different

Dementia is often the first symptom of Alzheimer’s disease. This may include memory loss, difficulty with decision-making or problem-solving, and trouble planning or reasoning.

People living with Parkinson’s disease may eventually experience some of these same symptoms. However, it usually happens much later in the course of the disease. This is called Parkinson’s disease dementia (PDD).

Some people with Parkinson’s may start having symptoms of dementia within a couple of years of developing motor symptoms. However, most people live with motor symptoms for many years before they experience dementia.

In rare cases, people with Parkinson’s may experience dementia symptoms first or alongside their motor symptoms. When this happens — along with other signs — it may be diagnosed as dementia with Lewy bodies, or Lewy body dementia. This is not the usual progression for someone diagnosed with Parkinson’s disease, though.

4. Dementia Itself May Look Different

While dementia can affect people with both Parkinson’s and Alzheimer’s, it often looks different in each condition. People living with Alzheimer’s disease usually struggle to form new memories. They may, for instance, remember things that happened years ago but forget something that just happened an hour ago.

People with Parkinson’s, on the other hand, often have slower thinking and may have trouble with tasks.

5. Parkinson’s Has Specific Movement Symptoms

Parkinson’s disease is closely tied to motor symptoms, as noted above. In fact, doctors look for at least two out of three specific motor symptoms to diagnose it. These symptoms are:

• Slower movements, called bradykinesia — People living with Parkinson’s may not be able to move as quickly as they used to, even when they try.
• Muscle tremors while at rest — This looks like shaking and often starts in the fingers and hands, though it can affect the feet, jaw, or other parts of the body, too.
• Muscle rigidity — Muscles might feel stiff even when they shouldn’t. They might feel tense, and movement can become jerky.

While Alzheimer’s disease can eventually affect the way you move, it doesn’t cause these symptoms. Also, these motor symptoms are often the first symptoms of Parkinson’s, but changes in movement ability usually show up much later in Alzheimer’s disease.

Talk With Others Who Understand

At myALZteam, you’ll find the social network for people with Alzheimer’s and their loved ones. On myALZteam, members come together to ask questions, give advice, and share their stories with others who understand life with Alzheimer’s.

Have you lived with or cared for people diagnosed with both Alzheimer’s and Parkinson’s? What similarities and differences stood out to you? Share your experience in the comments below, or start a conversation by posting on your Activities page.