The objective of this study is to investigate the effects of relatively long-term use of a wearable device that provides personalized and intelligent cues (e.g. only when FOG is detected) on FOG.

The objective of this study is to investigate the effects of relatively long-term use of a wearable device that provides personalized and intelligent cues (e.g. only when FOG is detected) on FOG. It is hypothesized that the use of this device will reduce FOG in the home and in the community more than in a group of freezers who only receive basic gait information unrelated to FOG-episodes.

This study is a single- blinded bi-centric randomized controlled trial, consisting of 4 weeks of intervention, pre- and post- assessments and free-living monitoring. For this purpose, the DeFOG system was developed through a collaboration between our research group, the Sourasky Medical Center Tel Aviv and mHealth Technologies Bologna, Italy. The system consists of a smartphone, 2 foot-mounted inertial measurement units (IMU's) and earphones which enable transmitting feedback and auditory cues for gait, when FOG is about to occur. The patients will be randomized into an intervention group (DeFOG group) or a control group (N=31 per group). All patients will wear the DeFOG system (mHealth Technologies, mHT) and both groups will receive feedback about the daily number of steps produced. But, only the DeFOG group will receive cueing following detection of FOG. The cueing consists of a metronome, and if FOG persists, also a verbal instruction will be delivered. A therapist will personalize the settings of the DeFOG system and will support the patients in using the system (for instance in coping with false positives). Pre- and post- assessments will be performed by a blinded researcher, both before and after taking medication (in OFF and ON medication state, respectively), consisting of FOG-provoking tasks and questionnaires. During the post-assessment, the FOG provoking protocol will be repeated in both groups with and without the cueing option of the DeFOG system in the home situation.

If therapists involved in the trial note an increase of falls throughout the trial, then it can be decided to involve an interim analysis of the data monitoring committee.

Inclusion criteria:

1. Clinical diagnosis of Parkinson's disease (PD) (n=31 per site) according to the UK PD Society Brain Bank criteria
2. Modified Hoehn & Yahr Stage I to IV in the ON-state;
3. Age between 40 and 90 years;
4. Ability to walk 5 minutes while unassisted by another person;
5. Mini-Mental State Examination (MMSE) score of >= 21 or > 16 on the 26-item MMSE screening;
6. Stable PD medication during the previous month and no medication change foreseen for the next 6 weeks.
7. Self-reported freezing of gait (FOG) severity of at least 1 FOG episode per day, based on Characterizing of Freezing of Gait Questionnaire, irrespective of FOG occurring ON- or OFF-medication.

Exclusion criteria:

1. Participation in another clinical study;
2. Use of a cueing device as normal practice;
3. A fall frequency of more than once a day;
4. Acute musculoskeletal or other neurological or cardiovascular conditions affecting gait or any other medical condition which, in the opinion of the investigator, may prevent completing the protocol;
5. Hearing problems, precluding use of auditory feedback from the DeFOG system;
6. The occurrence of any of the following within 3 months prior to informed consent: orthopedic surgery of the lower extremity, myocardial infarction, hospitalization for unstable angina, coronary artery bypass graft, percutaneous coronary intervention, implantation of a cardiac resynchronization therapy device, implantation of deep brain stimulation;
7. Substance abuse, major depressive disorder or clinical apathy that affects daily walking activity or may interfere with the patient's compliance;
8. Inability to walk without a rollator indoors;
9. Use of a Duodopa® or apomorphine injections, jeopardizing OFF-medication assessments;
10. Absence of clinically observed FOG during the FOG-provoking assessment at the pre-intervention assessment (T1).

Prior to randomization, all participants will be informed that the goal of the study is to compare the effects of two types of feedback about physical activity on freezing of gait. By withholding information about the cueing intervention, we hope that the participants in the control group will not realize that they are in the control group, in order to avoid a lack of motivation in this group. The intervention group will probably become unmasked after group allocation, as the cueing therapy was not mentioned in the informed consent.

During the post-assessment, the FOG provoking protocol will be performed with and without cueing. This induces the risk of the investigator/outcome assessor becoming unmasked, as patients in the control group may mention that this cueing option is something they haven't experienced during the intervention period. In order to prevent this, the therapist will ask patients in the intervention group to also act surprised to the cueing modality.