How Parkinson's and Alzheimer's Differ

Medically Reviewed

Diagnosing cognitive impairment in Parkinson’s disease patients is made challenging by the fact that it is often difficult to determine whether certain symptoms are due to Parkinson’s or Alzheimer’s disease. Here are some key ways in which these two diseases differ:

Parkinson’s disease

1. Dual impairments. There is a greater impact on social functioning with Parkinson’s due to the combination of movement and cognitive impairments.

2. Dementia comes much later. The dementia component of Parkinson’s typically occurs after several years of movement impairment.

3. Hallucinations. These are more common in both Parkinson’s disease dementia and Lewy body dementia than in Alzheimer’s disease, and typically involve people or animals that may or may not be threatening to the patient.

4. Dementia is not a given. Dementia may or may not occur in people with Parkinson’s. Upward of 30 percent of patients with Parkinson’s do not develop dementia.

Alzheimer’s disease

1. No movement component. Alzheimer’s is primarily a memory disorder that rarely includes any type of movement impairments.

2. Dementia is the hallmark of the ailment. People with this fatal brain disease become confused about time and place, have difficulty remembering how to perform simple tasks, and have difficulty recognizing people.

3. Different causes. In Alzheimer’s, it’s the neurotransmitter acetylcholine that is progressively lost over the course of the disease. Worsening memory and intellect can progress and become severe without any effect on the patient’s movement ability. Parkinson’s disease results from the loss of dopamine-producing neurons needed to control movement and coordination.