Man sitting on chair and thinking

Some people with Parkinson’s disease (PD) experience mild cognitive impairment. Feelings of distraction or disorganization can accompany cognitive impairment, along with finding it difficult to plan and accomplish tasks.

It may be harder to focus in situations that divide your attention, like a group conversation. When facing a task or situation on their own, a person with PD may feel overwhelmed by having to make choices. They may also have difficulty remembering information or have trouble finding the right words when speaking. These changes can range from being annoying to interfering with managing household affairs.

To some degree, cognitive impairment affects many people with PD. The same brain changes that lead to motor symptoms can also result in slowness in memory and thinking. Stress, medication and depression can also contribute to these changes.

Symptoms of mild cognitive impairment (MCI) often do not interfere with home and work life. They may not even be noticeable, but can be detected through testing. Doctors used to believe that cognitive changes did not develop until middle to late-stage PD, but recent research suggests that mild changes may be present at the time of diagnosis.

Tell your doctor if you have concerns about cognitive changes. You may need to change your medication or see a neurologist or neuropsychologist for assessment. An occupational therapist can also help you find strategies for adapting and coping with these symptoms. A speech therapist can help with language difficulties.

In general, mental and motor decline tend to occur together as the disease progresses. Significant cognitive impairment in PD is often associated with:

  • Caregiver distress
  • Worse day-to-day function
  • Diminished quality of life
  • Poorer treatment outcomes
  • Greater medical costs due to nursing home placements
  • Increased mortality

Cognitive impairment is different from dementia, which is when cognitive impairments occur in more than one area of cognition, leading to more severe loss of intellectual abilities that interferes with daily, independent living. While 20% to 50% of people with PD will experience mild cognitive impairment, not all lead to a dementia diagnosis.

Two long-term studies suggest that many people with PD will eventually develop a mild form of dementia as the disease progresses, usually many years after their initial diagnosis. One medication, Exelon (rivastigmine tartrate), can treat dementia in PD. Other medications are being studied.

What causes cognitive changes in people with PD?

One cause is a drop in the level of dopamine, the neurotransmitter that is involved in regulating the body’s movements. However, the cognitive changes associated with dopamine declines are typically mild and restricted.

Other brain changes are likely also involved in cognitive decline in PD. Scientists are looking at changes in two other chemical messengers — acetylcholine and norepinephrine — as possible additional causes of memory and executive function loss in Parkinson’s. 

Effects of Cognitive Changes

The cognitive changes that accompany Parkinson’s early on tend to be limited to one or two mental areas, with severity varying from person to person. Areas most often affected include:

How are cognitive issues diagnosed?

Common ways to assess and diagnose cognitive disorders:

  • Interview the person with PD.
  • Ask family members or care partners about their observations.
  • Administer cognitive screening tests such as the Mini-Mental State Examination (MMSE) or Montreal Cognitive Assessment (MOCA). The neurologist will ask questions that evaluate the person’s understanding of where and who they are, the date and year, attention, memory, language and problem-solving skills.
  • A neurologist may suggest seeing a clinical neuropsychologist for a more detailed assessment.
  • Neuropsychological assessment can be an important diagnostic tool for differentiating PD from other illnesses such as Alzheimer's disease, stroke or dementia.

How are cognitive changes in PD different than Alzheimer’s disease?

Overall, dementia produces a greater impact on social and occupational functioning in PD than Alzheimer’s due to the combination of motor and cognitive impairments.

There is some overlap between symptoms and biological changes seen in Alzheimer’s and PD. However, it is less likely for both disorders to occur at the same time. Development of dementia in people with PD represents progression of the disease, usually after several years of motor impairment.

Dementia may or may not occur in people with PD. According to recent research, 30% of people with Parkinson’s do not develop dementia as part of the disease progression.

See 10 Signs of Alzheimer’s.

What co-existing conditions affect thinking and memory?

There are other factors that can have a negative impact on a person’s cognitive skills, such as disorders of mood, anxiety and sleep. In some cases, these factors can make memory and thinking deficits worse, as well as directly affect a person’s quality of life.

Some medications used to treat PD have also been shown to have stimulating effects on thinking and energy levels (like selegiline (Eldepryl®) and amantadine).

Seeking Help for Cognitive Changes

Cognitive change is a sensitive issue. In fact, the doctor is often as hesitant to address this subject as the person with PD is to ask about it. Sometimes, the doctor will delay discussing cognitive impairment out of concern for the person who is still coping with the shock of a new PD diagnosis or struggling with motor symptoms.

For this reason, the person with PD often needs to be the one to initiate the conversation. Tell your doctor if you or your loved one is experiencing problems that upset the family or cause interruptions at work.

Cognitive issues are never too mild to address with your care team. A doctor can provide ways to help, often referring you to a psychiatrist, neuropsychologist, speech or occupational therapist for further evaluation and assistance. The neuropsychological evaluation can be particularly useful, especially in the early stages of a cognitive problem. Having this baseline test can help the doctor determine whether future changes are related to medications, the progression of the PD itself or to other factors such as depression.

When reporting symptoms of mild cognitive impairment, the doctor will first want to rule out causes other than PD, such as vitamin B-12 deficiency, depression, fatigue or sleep disturbances. It should be noted that PD does not cause sudden changes in mental functioning. If a sudden change occurs, the cause is likely to be something else, such as a medication side-effect.

If cognitive symptoms are traceable to PD, there are drug therapies available. Though developed for Alzheimer’s, these medications have been found to have some effect in PD. These include rivastigmine (the only medication approved by the FDA for dementia in PD), donepezil and galantamine. In addition, a person with attention difficulties that are due to daytime sleepiness may benefit from stimulants.

How are cognitive problems treated?

Much remains to be learned about the basic biology that underlies cognitive changes in PD. Researchers work towards the development of diagnostic tests to identify people who seem to be at greatest risk for cognitive changes and to differentiate cognitive problems in people with PD from those that occur in another disorder — related but different — known as dementia with Lewy bodies.

A combination of medications and behavioral strategies is usually the best treatment for cognitive problems in PD.

Tips for Care Partners

  • Offer help only when asked.
  • Prompt the person — for example, instead of asking, “Did anyone call?” ask, “Did Linda call?”
  • Say the name of the person and make eye contact when speaking to gain and hold attention.
  • Put reminder notes and lists in a prominent place.
  • Keep things in routine places.
  • To ensure medications are taken on time, provide a dispenser, perhaps with a built-in alarm.
  • Use photos on cell phone contact entries to prompt face-name association.
  • If the person is searching for a word, provide a cue, such as, “the word you are looking for probably begins with ‘d’.”
  • Do not finish the sentences of a person who needs more time to put them together.
  • When presenting the person with a list of actions, first verbalize them, then write them down.
  • Ask questions to moderate the conversation pace and allow catch up and reinforcement.

Page reviewed by Dr. Kathryn P Moore, Movement Disorders neurologist at Duke Health, a Parkinson's Foundation Center of Excellence.

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