Subtle Changes in How You Walk May Signal Parkinson's Nearly 7 Years Early

When your right leg moves forward, your left arm usually swings forward with it. That motion helps counter the twist of your body as you step.

Parkinson's disease can disrupt that coordination.

As the brain loses nerve cells that make dopamine, a chemical that helps control movement, muscles can stiffen and movements can slow.

A team at the University of New South Wales in Sydney wanted to know how early those effects might show up in an ordinary walk.

In people who later received a Parkinson's diagnosis, wrist recordings revealed differences in arm movement nearly seven years before diagnosis.

The study's joint first authors were Paulo Pelicioni, a researcher at the university's School of Health Sciences, and Sophie Waller, who is affiliated with its School of Clinical Medicine and the neurology department at Sydney's Prince of Wales Hospital.

They and their colleagues drew on the UK Biobank, a long-running health study that invited more than 100,000 volunteers to wear a wrist sensor for a week.

The team analyzed usable recordings from 73,413 people and followed them through their medical records for up to a decade. During that time, 314 received a Parkinson's diagnosis after wearing the sensor.

A wrist sensor registers the movement of a hand reaching for a cup as readily as it registers a swinging arm. The team used software called Watch Walk to find the stretches of the recordings that captured walking. It estimated how many steps people took, how fast they walked, and how regularly their steps fell.

The direction the wrist pointed and the way it moved helped the software distinguish a swinging arm from a hand held near the head or in front of the body.

The researchers grouped the people who later received a diagnosis by how much time passed between the recording and their diagnosis. Those diagnosed within 40 months of wearing the sensor averaged about 4,000 steps a day, compared with about 6,400 among people with no recorded Parkinson's diagnosis during follow-up.

The gap was smaller among people whose diagnosis came later. People who later received a diagnosis also tended to reach lower top walking speeds. The rhythm of their steps and the share of their walking done in longer stretches differed, too.

The wrist told part of the story that a step count alone would miss. People who went on to receive a diagnosis tended to spend less of their walking time swinging their arms naturally. The team could see a difference even in recordings made nearly seven years before diagnosis.

Scientists have also looked for early signs of Parkinson's in blood proteins. Wrist recordings offer a view of how people move outside the exam room. If the findings hold up in other groups, the recordings could help researchers identify people to invite into trials of treatments designed to slow the disease in its early stages.

For now, the results describe differences between groups. They can't tell an individual whether they'll develop Parkinson's. Pain, medication, and other health conditions can also affect how someone walks.

The team recorded each person's movements during a single monitoring period, so it couldn't tell when anyone's arm swing began to change. A follow-up study could track the same people at regular intervals to see how their walking changes over time.

Three authors disclosed an agreement with SpaceTalk Inc. to commercialize the Watch Walk algorithm and may receive royalties. Research groups can use the algorithm for free.

The research was published in the Journal of Neural Transmission.