Telerehabilitation is a promising tool for treating and preventing further disease progression in Parkinson's disease (PD) [1, 2]. First studies in people with PD (PwPD) verified the feasibility of home-based digital cognitive training [3-7]. Progression in cognitive impairment and the onset and worsening of problems with complex everyday tasks are hallmarks of the prodromal phase of Parkinson's disease dementia (PDD). Consequently, the risk of PDD conversion is dramatically increased for PwPD with both mild cognitive impairment (PD-MCI) and complex activities of daily living (ADL) problems related to cognitive impairment [8]. Therefore, this group may be a promising target group for interventions, as they are at risk for serious and rapidly progressive cognitive deterioration.

PwPD with PD-MCI show deficits in motor-cognition [9] and attentional-control, both of which affect ADL [10]. Dual-task cognitive trainings (DCT) shows great potential to lower down the disease process [11, 12], but so far no home-based DCT with the primary endpoint of complex ADL and cognition has been conducted in PwPD. We adapted an on-site DCT to improve both physical and cognitive function in PwPD [13]. The training will be conducted as a telerehabilitation training in PwPD with PD-MCI and cognitive ADL impairment, identified with the Functional Activities Questionnaire (FAQ). Of PwPD with PD-MCI who have more cognitive rather than motor associated ADL dysfunction (reflected by a value of the FAQ quotient > 1.008), nearly 50% develop dementia (PDD) within three years [8].

In our single-center randomized, controlled non-pharmacological intervention, 42 PwPD with PD-MCI and FAQ quotient >1.008 will be assessed with pre-(T0) and post(T1), 6-months (T2) and 12-month follow-up (T3) testing. After 1:1 randomization to either the experimental DCT or the control motor training (CMT), both groups will leg-cycle safely in a comfortable chair on a bicycle ergometer, 3 times a week for 30 minutes. While cycling, the DCT group will additionally perform digital cognitive training on a tablet, covering attention, working memory and executive function. The cognitive training will automatically adapt to performance levels and is remotely accessible. The training is aimed to enhance cognition as well as ADL and to prevent its further decline, with an emphasis on maintaining ADLs in the prodromal stage of Parkinson's disease dementia (PDD).

Inclusion Criteria:

• PD diagnosis confirmed by a neurologist
• PD diagnosis at least for one year
• Age between 51-80 years
• German as their mother tongue
• Diagnosis of PD-MCI according to the Level II criteria of the Movement Disorder Society
• Cognitive ADL impairment as defined by the FAQ quotient
• An informant who has given consent to provide information about the participant's activities of daily living (ADLs) and who lives in the participant's home.
• Access to a WIFI Network at home
• Unimpaired or corrected vision and hearing
• Appropriate text comprehension and reading ability
• Ability to communicate well with the investigator, to understand and comply with the requirements of the study
• Provide written informed consent to participate in the study and understand the right to withdraw consent at any time without prejudice to future medical care

Exclusion Criteria:

• Diagnosis of PDD
• Intake of anti-dementia drugs
• Deep brain stimulation
• History of brain disease other than PD (e.g. head trauma, stroke, encephalitis) also including muscular diseases (e.g. myestenia gravis or myopathy)
• Pre-existing condition that limits limb movement (e.g. muscular injuries, knee and hip disorders
• severe cardiovascular diseases with heart failure
• severe respiratory diseases (e.g. asthma and lung disease)
• severe other accompanying illnesses with impairment of lung function
• renal insufficiency
• acute stage of infectious disease
• acute stage of cancer
• other disease with pronounced physical weakness
• History of brain disease other than PD, e.g., head trauma, stroke, encephalitis
• Alcohol, medication, or drug dependency or abuse (except for nicotine)
• Signs of severe depression indicated by either the 15 item version Geriatric Depression Scale (≥ 5 points)
• Acute psychosis
• Any disability or issues that may prevent the subject from completing the informed consent form or other study requirements
• Other neurodegenerative disease which renders the subject unable to communicate well with the investigator or to understand and comply with the requirements of the study
• Participation in any clinical investigation of a new compound or therapy within 4 weeks prior to baseline visit, and any other limitation of participation based on local regulations

Data sharing with other researchers requiere the permission of our ethic committee and a data transfer agreement

IPD will be available upon request

Data can be requested by the primary contact persons of this study