Apple Devices Identify Early Parkinson's Disease

Daniel M. Keller, PhD

September 24, 2021

Apple Watches and iPhones can differentiate between individuals with early, untreated Parkinson's disease (PD) and healthy controls, new research shows.

Results from the WATCH-PD study show clear differences in a finger-tapping task in the PD vs control group. The finger-tapping task also correlated with "traditional measures," such as the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS), investigators report.

"And then the smartphone and smartwatch also showed differences in gait between groups," lead investigator Jamie Adams, MD, University of Rochester, New York, told Medscape Medical News.

The findings were presented at the virtual International Congress of Parkinson's Disease and Movement Disorders 2021.


The 12-month WATCH-PD study included 132 individuals at 17 Parkinson's Study Group sites, 82 with PD and 50 controls.

Participants with PD were untreated, were no more than 2 years out from diagnosis (mean disease duration, 10.0 ±7.3 months), and were in Hoehn and Yahr stage 1 or 2.

Apple Watches and iPhones were provided to participants, all of whom underwent in-clinic assessments at baseline and at months 1, 3, 6, 9, and 12. The assessments included motor and cognitive tasks using the devices, which contained motion sensors.

The phone also contained an app that could assess verbal, cognitive, and other abilities. Participants also wore a set of inertial sensors (APDM Mobility Lab) while performing the MDS-UPDRS Part III motor examination.

In addition, there were biweekly at-home tasks. Questions and tests on the phone assessed symptoms of mood, fatigue, cognition, and falls as well as cognitive performance involving perceptual, verbal, visual spatial, and fine motor abilities. Both the watch and iPhone were used to gauge gait, balance, and tremor.

Ages of the participants were approximately the same in the PD and control groups (63.3 years vs 60.2 years, respectively), but male to female ratios differed between the groups. There were more men in the PD cohort (56% men vs 44% women) and more women in the control cohort (36% vs 64%; P =.03).

Between-Group Differences

Results showed that MDS-UPDRS total scores and on all individual parts of the rating scale were significantly better for the control group (lower scores are better), as shown in the following table.

Table 1. Between-Group Baseline MDS-UPDRS Mean Scores

Score PD Group Control Group P value
Total 35.0 6.0 < .001
Part I 5.4 2.9 < .001
Part II 5.5 0.4 < .001
Part III 24.1 2.7 < .001


Similarly, the control group performed better than the PD group on the Montreal Cognitive Assessment (MoCA), with higher scores showing better performance on the 0 to 30 scale (28.1 vs 27.6, respectively).

Touchscreen assessments on the phone also showed group differences in a finger-tapping task, with more taps by the control group than by the PD group. The difference was more pronounced when the dominant hand was used.

The median numbers of taps in 20 seconds for the dominant hand were 103.7 for the PD cohort vs 131.9 for control cohort (P < .005); and for the nondominant hand the numbers of taps were 106.6 vs 122.1 (P < .05), respectively. The control group also scored better on tests of hand fine-motor control (P < .01) and on the mobile digit symbols modalities test (P < .05)

Measures of gait in a one-minute walk test also showed group differences.

"The five gait measures that differed most were cadence, which is steps per minute, double support, arm swing amplitude, arm swing variation, and turn duration," Adams said.

Table 2. Mean Gait Measurements at Baseline

Gait measure Control Group PD Group Pvalue
Cadence (steps/min) 113.1 107.6 < .05
Double support* (sec) .27 .28 < .05
Arm swing amplitude (degrees) 49.3 25.9 < .005
Arm swing variability (degrees) 11.3 7.5 < .005
Turn duration (sec) 2.2 2.5 < .005

*Double support: period of gait cycle with both feet in contact with the floor

"Tremendous Interest"

Commenting on the findings for Medscape Medical News, Ludy Shih, MD, MMSc, Boston University School of Medicine, Boston, Massachusetts, noted that in the future, devices such as the ones used in this study may help clinicians remotely monitor their patients' PD conditions and response to therapy.

That would "eliminate some of the transportation barrier for people with Parkinson's," said Shih, who was not involved with the research.

Additionally, the devices can give objective measurements, reducing inter-rater variability in assessment of movements, she noted.

"I think there's tremendous interest in using digital measures to pick up on subtle disease phenotypes earlier than a clinical diagnosis can be made," Shih said.

She also referred to literature "going back a few decades" showing that finger tapping can be used as a pharmacodynamic measure of how well a patient's dopaminergic medications are working, so the devices may be a way to remotely assess treatment efficacy and decide when it is time to make adjustments.

Shih added that she thinks regulatory agencies are now open "to consider these as part of the totality of evidence that a therapeutic [device] might be working."

Whether these would need to be professional grade and approved as medical devices or if patients could just buy smartwatches and smartphones to generate useful data is still a question, she said. Already, there are several Parkinson's apps that the public can download to track symptoms, improve voice, provide exercises, find support groups or research studies, and more.

Shih predicted that the biweekly at-home tasks, as in the current protocol, could be a burden to some people. If only a segment of the population were willing to comply, it could call into question how generalizable the results were, she added.

"There's even a prior publication showing that compliance rate really dropped like a rock," she noted. However, for those people willing to perform the tasks on a regular schedule, the results could be valuable, Shih said.

Adams concurred, saying that she had received feedback from some of her study participants that the biweekly tasks were a bit much.

The study was supported by Biogen and Takeda Pharmaceuticals. Adams receives research support from Biogen. Shih has disclosed no relevant financial relationships.

International Congress of Parkinson's Disease and Movement Disorders (MDS) 2021: Abstract 364. Presented September 17-22, 2021.

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