What is parkinson's?
Parkinson's disease is the second most common brain disease in the world, after Alzheimer's. It affects about 1 in 100 people over the age of 60, though it can occur much younger.
The four things most people associate with Parkinson's are: a tremor (a shaking, usually in the hands, that happens at rest), stiffness in the muscles, slowness in starting and making movements, and problems with balance. All four of these come down to the same cause: not enough dopamine. Without it, the movement-coordination system in the brain starts sending the wrong signals at the wrong times, or not enough signal at all.
But Parkinson's is more than just a movement disorder. Many people notice problems with their sense of smell, disturbed sleep (sometimes acting out their dreams), constipation, and feelings of depression or anxiety, often years or even decades before any movement symptoms appear. This tells us that the disease starts much earlier than we used to think, and in parts of the brain outside the movement system.
how is movement controlled?
Deep inside your brain, there is a small region called the basal ganglia. Think of it as your brain's movement coordinator: it helps decide which movements to make, how big they should be, and when to stop.
For the basal ganglia to do its job, it needs a steady supply of a chemical messenger called dopamine. Dopamine acts a bit like oil in an engine. Without it, things that should run smoothly start to grind and stall.
The dopamine that serves this part of the brain comes from a cluster of nerve cells in the midbrain called the substantia nigra. This is Latin for "black substance," because when you look at a healthy brain, this area appears dark due to the pigment in those cells.
In Parkinson's, it's these specific cells that gradually die off. And as they go, dopamine levels fall, taking the brain's ability to control movement with them.
Why do these cells die?
Researchers have pieced together a lot of the story, even if some chapters are still being written.
A protein that gets stuck together in clumps
Inside the dopamine-producing nerve cells, a small protein called alpha-synuclein is normally found floating freely, helping to manage the tiny sacs (called vesicles) that store and release dopamine.
In Parkinson's, alpha-synuclein starts to fold into the wrong shape and stick to itself, forming toxic clumps.
These clumps, when they build up inside a nerve cell, are called Lewy bodies, named after the scientist who first described them.
Think of it like a protein that's supposed to be a loose, flowing scarf suddenly tangling itself into a tight knot. Not only is it no longer useful, it's also getting in the way of everything else the cell needs to do.
Lewy bodies are found in the nerve cells of almost everyone with Parkinson's. They disrupt the cell's normal workings and eventually cause it to die.
The disease may actually start in the gut
One of the most surprising recent discoveries is that Parkinson's may not begin in the brain at all. There is growing evidence, backed by a scientist named Heiko Braak, that the disease starts in the gut's own nervous system, or possibly in the nose, and then travels up to the brain along the body's internal communication highways.
This is why constipation and smell problems are so often the very first signs of Parkinson's. By the time the first tremor appears, the disease has often been quietly developing for ten years or more.
Inflammation makes things worse
The brain has its own immune cells, called microglia, whose job is to spot and deal with threats. In Parkinson's, microglia become chronically activated, stuck in a state of high alert, and start releasing substances that damage the very neurons they're meant to protect. This ongoing inflammation speeds up the loss of dopamine-producing cells.
The cell's energy supply becomes unreliable
Dopamine-producing cells are particularly needy when it comes to energy. Making and releasing dopamine is an energy-hungry process, and it also naturally generates chemical waste products that can damage the cell if they're not cleaned up efficiently.
In Parkinson's, the cell's energy generators (mitochondria) begin to fail, producing less energy and more damaging waste.
At the same time, the cell's waste disposal systems slow down. It's as if the bin collectors have gone on strike while the household is producing more rubbish than ever.
parkinson's progression
Parkinson's tends to develop slowly, and the experience varies a lot from person to person.
The tremor in Parkinson's is distinctive. It tends to happen when the hand is at rest, rather than during movement, and often has a rhythmic "pill-rolling" quality. Stiffness can make the body feel rigid, and a common early sign is a reduced swing of one arm while walking. Slowness of movement (known as bradykinesia) is often the most disabling feature. Getting up from a chair, turning around, and starting to walk can all feel like they require enormous effort. Handwriting tends to get smaller. Facial expressions may reduce, giving the impression of a blank or masked face, which can be misread as a lack of emotion.
With appropriate support, many people with Parkinson's continue to live active, fulfilling lives for many years after diagnosis.
current research
Targeting the protein clumps before they spread
If alpha-synuclein clumps travel between nerve cells and spread the disease like a slow domino effect, then stopping that spread could halt or slow Parkinson's in its tracks. Several clinical trials are now testing antibodies designed to grab hold of alpha-synuclein outside the cells and clear it away before it can do more damage.
A surprising lead from diabetes drugs
A class of drugs used to treat type 2 diabetes, called glucagon-like peptide-1 (GLP-1) receptor agonists (which includes drugs like semaglutide), have shown unexpectedly promising effects on Parkinson's in early trials. Scientists believe they may help protect nerve cells and reduce inflammation. Large clinical trials are now underway.
Catching it early
If the disease really does start years before symptoms appear, then the window for really effective treatment could be much earlier than diagnosis. Research into early biomarkers, such as measurable signs in blood, spinal fluid, or brain scans that show the disease is beginning, is one of the most exciting areas of Parkinson's research today.
