Parkinson's disease dementia

Parkinson's disease is best known as a movement disorder. It causes shaking, stiffness, slow movement and balance problems. But over the years, many people with Parkinson's also have changes in thinking and memory. When those changes become serious enough to get in the way of daily life, doctors call it Parkinson's disease dementia (PDD).^1,4

Knowing the early signs helps. Treatment can ease some symptoms, and knowing which medicines to avoid and how to prevent falls keeps the person safer.

What is Parkinson's disease dementia?

In Parkinson's disease, clumps of a protein called alpha-synuclein build up inside brain cells. These clumps are called Lewy bodies. They first harm the brain areas that control movement. Over time, they can spread to areas that handle thinking, attention and vision.¹

Parkinson's affects nearly 2 in 100 people over age 65. Close to one million Americans live with it.¹ Most people are first diagnosed in their early to mid-60s.⁴

Thinking changes often start small. About half of people with Parkinson's have mild cognitive impairment. This means thinking problems that others notice but that do not yet stop daily life.³ In people whose thinking is normal at diagnosis, about 3 in 10 develop mild cognitive impairment within five years.¹ Read more about mild cognitive impairment.

On average, dementia appears about 10 years after Parkinson's starts, though this varies a lot.¹ At any one time, about 3 in 10 people with Parkinson's have dementia. That is about 4 to 6 times the risk of people the same age without Parkinson's.²

The one-year rule: Parkinson's dementia or Lewy body dementia?

Parkinson's disease dementia and dementia with Lewy bodies (DLB) are close cousins. Both are caused by the same Lewy body changes in the brain. Over time, people with either one tend to have similar thinking, movement, sleep and behavior problems.¹⁴ Together they are often called Lewy body dementia.

Doctors tell them apart mainly by which came first:^1,2

Experts admit the one-year cutoff is not based on a clear difference in the brain. It is a practical rule so everyone uses the same labels.² Treatment advice and medicine warnings are much the same for both. See Lewy body dementia.

Signs and symptoms

Parkinson's disease dementia often looks different from Alzheimer's disease. Memory loss is usually not the first or biggest problem. Instead, people tend to have trouble with:^2,3

• Attention. Focus may come and go. Some days or hours are much better than others.
• Planning and thinking speed. Starting tasks, solving problems, following steps and switching from one task to another become hard. Thinking may feel slow.
• Seeing and judging space. The person may misjudge distances, have trouble finding their way, or misread what they see, especially in dim light.
• Memory. Recalling new information is harder. But hints and reminders often help, which is less true in Alzheimer's.
• Speech. Speech may be soft or muffled, and finding words can be hard. Basic language skills are usually kept longer.

Mood, behavior and sleep can change too:^1,2

• Apathy (loss of interest and drive), depression and anxiety
• Visual hallucinations (seeing things that are not there)
• Delusions (fixed false beliefs), such as believing a spouse is unfaithful or a stranger lives in the house
• Daytime sleepiness, and acting out dreams during sleep (REM sleep behavior disorder)

Dementia is diagnosed only when these problems affect daily life on their own, not just because of the shaking or slowness of Parkinson's.²

Who is at higher risk?

Older age is the biggest risk factor. Dementia is also more likely with more severe movement symptoms, thinking problems at diagnosis, early hallucinations, a lot of daytime sleepiness, and walking and balance problems such as freezing and falls.¹ None of these means dementia is certain. They are reasons to watch for changes and tell the doctor early.

How doctors diagnose it

No single test can confirm Parkinson's disease dementia.¹ The doctor, often a neurologist or movement disorder specialist, confirms the Parkinson's diagnosis and when movement symptoms began. They ask the family about changes in thinking, mood, sleep and daily tasks, and use memory and thinking tests.² They also look for other causes, such as depression, infection or a new medicine. See treatable conditions that look like dementia and which specialist to see.

Treatment for thinking and memory

No treatment can slow or stop the brain damage in Parkinson's disease dementia. Care focuses on easing symptoms and keeping the person safe. Deep brain stimulation, a surgery that helps some Parkinson's movement symptoms, is not advised for people with this dementia.¹

How much do these medicines help? A Cochrane review pooled four trials in Parkinson's disease dementia, plus two related trials. Overall, the medicines helped thinking, behavior, daily activities and the doctor's overall rating a small amount.⁶ For example, about 1 in 5 people on the medicine had a clear overall improvement, compared with about 1 in 7 people on a placebo (a look-alike with no medicine).⁶ Moderate evidence

Side effects. People on these medicines were more likely to have side effects and to stop treatment.⁶ Nausea, vomiting, less appetite and weight loss are common, and the heart rate can slow.⁵ Tremor (shaking) may get a little worse: about 9 in 100 people on the medicine reported more tremor, compared with about 3 in 100 on a placebo.⁶

Parkinson's medicines and thinking. Carbidopa-levodopa and some other Parkinson's medicines help movement but can worsen hallucinations and confusion.^1,4 The doctor may need to balance movement against clear thinking. Talk with your doctor or pharmacist before changing anything. Stopping some Parkinson's medicines suddenly can be dangerous.¹³

Hallucinations and delusions

About 2 to 4 in 10 people with Parkinson's have hallucinations or delusions at some point. They become more common as the disease goes on.¹¹ Most are visual, such as seeing people or animals. Some people sense someone nearby, or mistake a coat on a chair for a person.¹¹

Common triggers include:¹¹

• Parkinson's medicines, including carbidopa-levodopa, dopamine agonists, amantadine and anticholinergic drugs
• Delirium, a sudden confused state often caused by an infection such as a urinary tract infection or pneumonia
• Poor sleep, vivid dreams or acting out dreams
• Poor eyesight, depression and the dementia itself

What doctors usually do first. The doctor checks for infection or other illness. Then they often adjust Parkinson's medicines, one at a time.¹¹ If hallucinations are mild and not upsetting, the person may not need a new medicine.

Pimavanserin (Nuplazid)

Pimavanserin was approved by the FDA in 2016 for hallucinations and delusions linked to Parkinson's disease.¹¹ It works on serotonin, a different brain chemical. Unlike most antipsychotics, it does not block dopamine.¹² This matters because blocking dopamine worsens Parkinson's.

In the main six-week study of 185 people, symptoms improved about twice as much with pimavanserin as with a placebo. It did not make movement worse.¹² Moderate evidence Side effects more common than with placebo included swelling of the legs or feet (7% vs 2%) and confusion (6% vs 3%).¹²

Pimavanserin can affect heart rhythm, so doctors avoid it in some people with heart rhythm problems.¹² Like all antipsychotics, it carries the FDA's strongest warning, a boxed warning. Older adults with dementia who take antipsychotic medicines have a higher risk of death. Pimavanserin is approved only when the hallucinations and delusions are linked to Parkinson's disease, not other dementias.¹²

Other options. Doctors may also use quetiapine or clozapine. Clozapine works well but needs regular blood tests, so it is usually saved for when other choices fail.¹¹

How to respond to a hallucination. Stay calm. Do not argue or try to prove it is not real. Say what you notice, offer comfort, and gently change the subject or the setting. Good lighting, especially in hallways and at night, can reduce scary misreadings.^3,11 See hallucinations, delusions and paranoia and medicines for agitation and behavior.

Falls: a major risk

About 6 in 10 people with Parkinson's fall each year.⁹ Some falls cause lasting harm to mobility and independence.¹⁰ Dementia adds to the risk. It makes it harder to pay attention to walking, and walking while distracted raises the chance of a fall.¹⁰

Other causes include shuffling, poor balance, "freezing" (feet that feel stuck to the floor), blood pressure that drops on standing, and medicines that cause sleepiness.¹⁰

Can rivastigmine help with falls? In a small trial, 130 people with Parkinson's who had fallen in the past year took rivastigmine or a placebo. They took it for 32 weeks. People on rivastigmine fell about 45% less often, and their walking was steadier. But nausea (31% vs 5%) and vomiting (17% vs 5%) were much more common.⁷ People with dementia were not included, and the authors said a larger trial was needed.⁷ A larger trial of 600 people in the United Kingdom, called CHIEF-PD, was set up to test this over 12 months.⁸ Promising

1. Tell the doctor about every fall, and about near-falls, dizziness on standing, or freezing.¹⁰
2. Ask for physical and occupational therapy. Therapists teach balance exercises, tricks for freezing, and safe use of a cane or walker.¹⁰
3. Keep moving. Regular exercise builds balance, strength and mobility.¹⁰ Ask about programs like strength and balance training or tai chi.
4. Make the home safer. Remove clutter, loose rugs and cords. Add grab bars in the bathroom and night-lights on the path to the toilet.¹⁰
5. Slow down. Stand up slowly, turn in wide steps, and keep hands free.¹⁰
6. Check eyes and ears, and consider a fall alert device or smart watch.¹⁰

See preventing falls and making the home safer for more.

Hospital stays need extra care

Hospitals can be risky for people with Parkinson's disease dementia.¹³

• Missed or late doses. Parkinson's medicines should be given on time, every time. Share a list of the exact times the person takes them at home. Stopping levodopa suddenly can cause a rare, life-threatening reaction.
• Unsafe medicines. Remind staff which drugs to avoid. Sleep medicines, strong pain medicines, muscle relaxants and bladder medicines can also cause confusion or hallucinations.

See hospital stays and emergency rooms.

Daily life and caregiving

Caring for someone whose movement and thinking both change is demanding. A few things can help:³

• Keep a steady daily routine. Speak slowly and simply, at eye level, one question at a time. Give extra time to answer.
• When the person seems upset, check for hunger, thirst, pain, tiredness or boredom.
• Plan early for driving, money matters and scams.
• Use a memory notebook to track dose times, falls and hallucinations.
• Take care of yourself too. See caregiver stress and burnout.

Both Parkinson's and the dementia get worse over time, but the speed varies widely.¹ Talk early about wishes for future care. See advance directives and palliative care.

Free help: The Parkinson's Foundation Helpline is 1-800-4PD-INFO (1-800-473-4636).³ The Alzheimer's Association 24/7 Helpline is 800-272-3900.

When to get help

Call the doctor soon if:

• Thinking, memory or behavior changes are new or getting worse
• Hallucinations or delusions start or become upsetting
• The person falls, nearly falls, or feels dizzy when standing
• Nausea, weight loss or more shaking start after a new medicine

Call the doctor the same day if confusion gets much worse over hours or a few days. This can be delirium from an infection or a medicine, and it is often treatable.¹¹

Call 911 for a fall with a head injury, a person who cannot get up, chest pain, fainting, sudden weakness or trouble speaking, or high fever with severe stiffness.

Education only. This page is general information written from the sources listed. It is not medical, legal or financial advice and does not replace a doctor, therapist or lawyer who knows your situation. How we write and check pages.