Alzheimer's vs Parkinson's Dementia: Key Differences Explained

As we or our loved ones age, we may be prone to memory loss and confusion. These problems can stem from many different underlying conditions. Such conditions affect the brain and impair its functioning. Both Alzheimer’s and Parkinson’s diseases disrupt the way the brain processes information.

Both conditions may lead to memory loss and confusion. They also cause problems with thinking and managing day-to-day life. Together, these symptoms are known as dementia.

How can you tell the difference between Alzheimer's and Parkinson's disease-related dementia?

For starters, Parkinson's usually begins with movement problems. Dementia happens at a later stage, at least a year after diagnosis. When you have Alzheimer's, on the other hand, the disease starts with memory loss and confusion.¹

How do early signs and symptoms differ?

Parkinson's disease generally begins as a movement disorder. Early symptoms include:²

• Tremors, often beginning in the hand or fingers
• Slowed movement, which may include foot dragging
• Rigidity and stiffness
• Difficulty writing
• Slowed automatic movements, like blinking, smiling, or swinging your arms when you walk

Alternatively, Alzheimer's disease generally begins with noticeable memory loss. Early signs and symptoms of Alzheimer's include:^3,4

• Trouble remembering familiar words
• Trouble remembering the names of people
• Misplacing important or common objects
• Increasing trouble with planning or organizing
• Challenges performing everyday tasks, such as balancing a checkbook

How do brain changes differ?

Specific brain changes define each condition. The key brain changes linked to Parkinson's disease and its related dementia are abnormal deposits of a protein called alpha-synuclein.
These deposits are known as Lewy bodies, named after the doctor who discovered them. As these proteins clump in the brain, normal brain cells begin to die off.¹

In Alzheimer’s disease, the primary brain changes include the buildup of different proteins called amyloid and tau. When amyloid proteins clump together, they form abnormal structures known as plaques. Abnormal groups of tau proteins form tangles.³

Over time, the buildup of these proteins causes normal brain cells to die, and affected parts of the brain may shrink.⁵

How are symptoms related to brain function different?

There is some overlap. However, the overall cognitive symptoms people experience are usually different.

Alzheimer's mainly affects language and memory at the outset. Parkinson's affects problem-solving, speed of thinking, memory, and mood.⁶

Unlike those with Alzheimer's disease, people with Parkinson's-related dementia often experience hallucinations, delusions, and paranoid thoughts. Both conditions can lead to depression, anxiety, and sleep disturbances.^4,6

How many people are affected by Alzheimer’s and Parkinson’s?

Parkinson's disease is thought to affect about 2% of Americans over 65. Of those, about 50% to 80% will go on to develop Parkinson's-related dementia.¹ The Parkinson's Foundation estimates that nearly 1 million Americans were living with Parkinson's by 2020. The disease affects 1.5 times more men than women.⁷

Approximately 5.8 million Americans are currently living with Alzheimer's disease. That number is expected to increase to 14 million by 2050.⁸ There is little difference between the numbers of men and women who develop Alzheimer's. However, there are more women living with the disease because women tend to live longer than men.³

Can you have both Parkinson's and Alzheimer's?

People who already have Parkinson’s disease and later develop signs of dementia are diagnosed with Parkinson’s dementia. However, if you initially have Alzheimer’s disease and then develop signs of movement difficulties, you can also have a diagnosis of Parkinson's disease.⁶