Parkinson’s disease is a progressive brain condition that develops as the nerve cells which make a chemical called dopamine are gradually lost. Dopamine is what lets your body move smoothly, so as those cells disappear, symptoms such as tremor and slowed movement start to show. “Progressive” means the symptoms don’t arrive all at once — they build slowly, over years.
What happens in the brain
The cells that make dopamine sit deep in the brain, in an area called the substantia nigraThe area of the brain where dopamine-producing nerve cells are concentrated. In Parkinson's, the cells here are gradually lost.Learn more. Their job is to supply dopamine to the basal gangliaThe brain circuit that controls movement. It relies on dopamine from the substantia nigra to keep movement smooth.Learn more, the circuit that keeps your movements smooth and coordinated. As those cells are lost, that circuit can no longer regulate movement properly.
One thing worth knowing: the movement symptoms usually only become noticeable after 60% to 80% of the substantia nigra neurons have already been lost or impaired. In other words, the process has been quietly underway for a long time before the first tremor appears. Why those cells are lost in the first place is still not fully understood.
How common is it
An estimated 1.1 million people in the U.S. are living with Parkinson’s disease, and nearly 90,000 people in the U.S. are diagnosed each year. Worldwide, the figure is estimated at more than 10 million people.
Age is the main risk factor — the chance of developing it rises as you get older. That said, it is not only a condition of later life: an estimated 4% of people with Parkinson’s are diagnosed before age 50, which is referred to as young-onset Parkinson’s. Men are about 1.5 times more likely to have Parkinson’s than women.
How it is diagnosed
There is no single blood test or scan that can confirm Parkinson’s disease. A neurologist takes a careful history — your symptoms, the medications you take, your family history — and examines how you move, your muscle strength, your walking and your balance. The diagnosis comes from putting all of that together. The core requirement is bradykinesiaA general slowing of movement. It is the hallmark motor symptom of Parkinson's disease.Learn more (slowed movement) together with at least one of the following: rest tremor, rigidityStiffness in the limbs, one of the main motor symptoms of Parkinson's disease.Learn more, or problems with balance.
When the picture is unclear, doctors may add supporting tests — a DaTscanA nuclear-medicine scan that images dopamine function in the brain. A negative result does not completely rule out Parkinson's disease.Learn more, which images dopamine function in the brain, or a Syn-One testA test on a small skin sample that looks for phosphorylated alpha-synuclein, a protein linked to Parkinson's disease.Learn more, which checks a small skin sample for a specific protein. MRI scans and blood tests may also be used, mainly to rule out other conditions.
What symptoms look like
The best-known symptoms are the motor ones: tremor in the hands, slowed movement (bradykinesia), and stiffness in the limbs (rigidity). But there are also non-motor symptoms — trouble sleeping, constipation, low mood — and because these are far less well known, people often don’t connect them to Parkinson’s at all. Our overview of symptoms goes through them in detail.
How it got its name
The name goes back to 1817, when the English physician James Parkinson observed six people and wrote the first detailed account of the condition, which he called “the Shaking Palsy.” His name was later attached to the disease, and it became the Parkinson’s disease we know today. Two centuries of research later, there is still no cure.
What you can do now
There is no cure yet, but medication and consistent exercise let many people manage their symptoms and carry on with daily life. How quickly it progresses, and which symptoms show up, differs from person to person — which is why staying in regular contact with your care team, and working out what fits you, matters more than any general rule.
This article is not a substitute for medical diagnosis or treatment. If you have questions about your symptoms or your diagnosis, please talk with your care team.
