Alzheimer's art

What is Parkinson’s disease?

Nearly one million people in the United States are living with Parkinson’s disease. Parkinson’s is the second-most common neurodegenerative disease after Alzheimer’s disease. The incidence of Parkinson's increased with age, but an estimated 4% of people with Parkinson's are diagnosed before age 50, and men are 1.5 times more likely to have Parkinson's than women.

Parkinson's disease is a progressive degenerative disorder of certain brain cells. The disease affects movements of the body and causes other problems, including dementia, as many individuals experience a decline in cognition that develops at least a year after diagnosis.

Typically, symptoms of Parkinson's start gradually, with a barely noticeable tremor on one hand. Tremors are common in individuals with Parkinson's, but the disorder also causes stiffness or slowing of movement. This slowing of movement means stiffness in the body, arms and legs, with the stiffness mostly concentrated in the shoulder or hips often seen as an early sign of Parkinson's. Also with the disorder, there is difficulty with balance and falls, and the individual might begin stooping, leaning or slouching while standing or walking.

Difficulty in sleeping is another symptom of Parkinson's, especially when the individual experiences sudden movements during sleep or becomes very restless and even acts out dreams while being in a deep sleep. Loss of smell could be another sign of Parkinson's in addition to a change in voice and facial features. Additionally, though constipation is often a recurring problem in aging adults, straining frequently during a bowel movement could be an early indication of Parkinson's and a symptom that should not be ignored. And, if the individual's handwriting has changed significantly, such as letter sizes are smaller and words are crowded together, then this change could be a sign of Parkinson's called micrographia.

Parkinson's disease is an extremely diverse disorder and like Alzheimer's disease, no two people experience Parkinson's in the same way. Many people with advanced Parkinson’s disease will develop dementia, and Parkinson’s disease shares some similar symptoms with Lewy body dementia in that individuals with both diseases may develop trembling in their hands, have difficulty walking and often feel weak and unsteady. 

Some studies have reported that the average time from onset of Parkinson’s to developing dementia is about 10 years. One large study found that about three-quarters of people who live with Parkinson's for more than 10 years will develop dementia. Before they develop dementia, they experience milder cognitive changes called mild cognitive impairment. Among individuals with normal cognition at Parkinson's diagnosis, about 30% will develop MCI after five years. However, cognitive changes and when they occur vary from person to person.

Certain factors at the time of Parkinson’s diagnosis may increase future dementia risk, including advanced age, greater severity of motor symptoms and mild cognitive impairment. For more information and resources, visit

Questions about Alzheimer's disease or related disorders can be sent to Dana Territo, author of  "What My Grandchildren Taught Me About Alzheimer's Disease," at