Parkinsons, Alzheimer's, Can Cause Similar Mental Decline

Parkinson’s disease (search) patients with dementia can lose their mental abilities at almost the same rate as people with Alzheimer’s disease (search), say Norwegian researchers.

Parkinson's disease belongs to a group of conditions called movement disorders. Symptoms of Parkinson's disease include tremors, rigidity, and imbalance. Symptoms vary from person to person, and not everyone is affected by all of the symptoms.

Not all people with Parkinson’s disease have dementia. However, dementia isn’t unusual with Parkinson’s disease, although it may take a decade to appear after Parkinson’s begins.

Parkinson’s disease occurs when brain cells that produce the chemical dopamine die. As a result, dopamine levels drop, garbling the brain's movement signals to the body.

Parkinson’s is usually diagnosed in people aged 50 or older (though it can occur in adults as young as 30). Advanced age is also the main risk factor for dementia. Alzheimer’s disease is the most common cause of dementia.

The latest study on Parkinson’s and dementia comes from scientists including Dag Aarsland, MD, PhD, of the geriatric psychiatry department at Norway’s Central Hospital of Roagland. Aarsland and colleagues studied 129 Parkinson’s patients who did not have dementia when they joined the study.

Participants took tests measuring thinking and memory skills three times: at their initial visit, and four and eight years later. They were screened by a neurologist, a geriatric psychiatrist, and a research nurse.

All participants lost at least some of their mental abilities over the years. But those with dementia had a steeper decline.

At the second visit, four years into the study, 49 patients were diagnosed with dementia. By the end of the eight-year study, 36 participants still did not have dementia. Participants were then about 73 years old, having had Parkinson’s for around 16 years, on average.

Patients without dementia lost little ground. Their average mental exam scores dropped about one point per year, on average. That’s about the same as healthy people, say the researchers.

“Forty-three percent of those who survived the eight-year study had no significant decline on the [tests] during the eight-year follow-up period,” they write in the December issue of Archives of Neurology.

Those with dementia weren’t as fortunate. Their test scores dropped an average of 2.3 points per year. Researchers say this rate of decline is similar to the rate seen in patients with Alzheimer's disease.

The decline was even faster among Parkinson’s patients in their first four years of dementia, say the researchers.

A few risk factors emerged. Old age, hallucinations, and more severe motor problems predicted faster mental decline in Parkinson’s patients.

More studies are needed, but the findings may help patients and caregivers prepare for future needs, say the researchers.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Aarsland, D. Archives of Neurology, December 2004; vol 61: pp 1906-1911. WebMD Medical Reference from Healthwise: “Parkinson’s Disease: Topic Overview.” WebMD Medical Reference from Healthwise: “Parkinson’s Disease: What Increases Your Risk.” WebMD Medical Reference from Healthwise: “Dementia: What Increases Your Risk.” WebMD Medical Reference from Healthwise: “Dementia: Topic Overview.” News release, JAMA/Archives.