Background: Mild Cognitive Impairment in Parkinson's disease (PD-MCI) is considered a predictor for the development of dementia, a major source of eventual treatment-refractory disability. Physical activity, which has proved effective in improving motor symptom, has also been proposed as a possible non-pharmacological intervention for preventing/delaying the onset of cognitive impairment in Parkinson's disease (PD).

Objectives: This study evaluates the effect of a 4-week rehabilitation therapy on cognitive functions in mid-stage PD-MCI patients.

Methods: 40 PD-MCI patients were randomized to receive physical therapy (PT) or no physical therapy (CT) according to a controlled single-blind design. Subjects in the PT group (n. 17) attended a rehabilitation program with 6 sessions/week, each lasting 60 minutes, for 4 weeks in addition to their usual pharmacological therapy; subjects in CT group (n. 22) received only pharmacological therapy. Cognitive and motor functions were assessed at baseline (T0) and at the end of the intervention period (T1) in both groups.

Non-pharmacological intervention may represent adjunctive therapy to medications in order to delay the onset of the cognitive deficits or dementia.

Previous studies observed a positive effect of cognitive training on cognition both in healthy elderly people and patients in the early stage of neurodegenerative diseases such as PD-MCI.

Several exercise interventions have proved to be effective on cognition in PD: tango, aerobic exercises and resistance exercise training. Physical activity may reduce dementia risk has not been established and issues regarding type, frequency and duration of exercises, as well as the best timing in which operate (disease stage and level of cognitive deterioration) remain unresolved.

Given the well-established irreversibility of cognitive impairment in neurodegenerative disorders, the scientific attention has shifted more and more on the identification of early interventions that, applied before the onset of deficits, may delay their full development. In this frame, the aim of the present study was to assess the effect of 4-week intensive physical training (6 session/week, 60 minutes/day) on both motor and cognitive impairments in patients with mid-stage PD-MCI.

Patients with idiopathic PD and MCI were recruited from the Neurorehabilitation Unit and Parkinson and Movement Disorders Unit of IRCCS Mondino Foundation.

All patients were treated with dopamine agonists or L-DOPA and had been on a stable therapy schedule for at least 3 months. No variations were allowed during the training and follow-up period. All groups were sex and age-matched.

The PD-MCI diagnosis was formulated on the basis of a comprehensive neuropsychological evaluation (baseline cognitive assessment - T0) according to the guidelines (level II criteria).

The following standardized tests assessing different domains were used:

• global cognitive function: Mini-Mental State Examination (MMSE) and Montreal Montreal Overall Cognitive Assessment (MoCA);
• memory: verbal (Verbal Span, Digit Span) and spatial (Corsi's block-tapping test - CBTT) span; verbal long-term memory (Logical Memory Test immediate and delayed recall) (Rey's 15-word test immediate and delayed recall); spatial long-term memory (Rey Complex Figure delayed recall - RCF-dr);
• logical-executive functions: non-verbal reasoning (Raven's Matrices 1947 - RM47) ; categorical abstract reasoning (Weigl's Sorting test); frontal functionality (Frontal Assessment Battery - FAB); semantic fluency (animals, fruits, car brands), phonological fluency (FAS);
• attention: visual selective attention (Attentive Matrices) (Carlesimo et al., 1995); simple speed processing and complex attention (Trail Making Test parts A - TMT A and part B - TMT B);
• visuospatial abilities: constructive apraxia Rey Complex Figure copy - RCF-copy.

At follow-up evaluation, we used a selection of previous tests in order to selectively investigate various features of executive functions. All the test scores were corrected for age, sex, and education and compared with the values available for the Italian population.

Motor performances were also assessed by means of MDS-Unified Parkinson's Disease Rating Scale, part III, Tinetti balance and gait score (Tinetti, 1986) and Hauser Index both at the baseline the follow-up evaluation.

This study is a prospective controlled, parallel-group randomized study. At baseline (T0) all the PD patients recruited underwent both cognitive and motor assessments. Patients enrolled were randomized to receive physical therapy (PT) or no physical therapy (CT). The physical therapy program consisted of 6 individual sessions/week, each lasting 60 minutes for 4 weeks in addition to their usual pharmacological therapy; while subjects in CT group received only pharmacological therapy. Cognitive and motor performances were evaluated after 4 weeks (T1) by means of the above-mentioned tests to detect the effect of physical therapy on both motor and cognitive performances (T0 vs T1).

Our physical therapy program included a variety of different exercise modalities (aerobic exercises, treadmill training and exercise intervention program) performed under the supervision of a physiotherapist, in order to facilitate goal-directed learning through cognitive engagement (learning through verbal feedback, cues, maintaining motivation and attention, improving awareness).

Inclusion Criteria:

• diagnosis of idiopathic PD according to UKPDBB criteria 26 and Hoehn & Yahr scale ≤3;
• presence of PD-MCI single- or multiple-domain;
• age between 50 and 85 years;
• educational level ≥ 5 years.

Exclusion Criteria:

• pre-existing cognitive impairment (e.g. aphasia, neglect);
• severe disturbances in consciousness;
• concomitant severe psychiatric disease or others neurological conditions (e.g. depression and behavioural disorders).