Background: Handwriting changes, such as micrographia, are recognised as an early manifestation of Parkinson disease (PD). Whilst isolated rapid eye movement sleep behaviour disorder (iRBD) is strongly associated with future PD diagnosis, changes in handwriting remain under-explored. Objective: To assess the handwriting of people with iRBD and develop a rating scale for detection of early disease clinical hallmarks. Methods: This is a cross-sectional study involving 33 people with polysomnography (PSG)-confirmed iRBD and 29 healthy controls. Participants copied a standard sentence using a pen and paper. A graphologist analysed each handwriting script blindly and designed a scale based on observed abnormal patterns which included: micrographia, sentence slope, hidden tremor, retracing, resting marks, irregular shape, excessive pen pressure, and inconsistent word spacing. Each item was scored 0/1 based on their absence/presence. Separately, three blinded movement disorders experts assessed the scripts based on their global clinical impression as well as using the developed rating scale. Results: People with iRBD were slower to complete the task than controls (76.70s (SD = 30.39) vs 61s (SD = 10.71); p=0.004). Hidden tremor was the most common feature amongst the iRBD group (72.0% vs 34.5%; p=0.005), followed by sentence slope (60% vs 24% p=0.005) and pen pressure (48% vs 14%; p=0.006). Micrographia was equally observed in both groups (iRBD 45.4%, controls 41.4% p=0.801). Classification accuracy of the scale for iRBD was higher than expert global assessment (AUC 0.76 vs AUC 0.62, p = 0.029). Conclusions: Writing speed, tremor, pen pressure and sentence slope are handwriting features that warrant further investigation to define early patterns in people with iRBD.

The authors have declared no competing interest.

This study did not receive any funding

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

Yes

The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

Ethics approval was granted by the Queen Square Research Ethics Committee (09/H0716/48). Participants received verbal and written information about the study and appropriately consented.

I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.

Yes

I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).

Yes

I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.

Yes

All data produced in the present study are available upon reasonable request to the authors