Rey Auditory Verbal Learning Test (RAVLT) was used to assess memory, with participants' scores recorded across five learning trials. Total scores ranged from 0 to 75, with a maximum raw score of 15 per trial. Higher scores indicate better memory performance.

Rey Auditory Verbal Learning Test (RAVLT) delayed recall assesses participants' memory based on the number of words recalled from a 15-word list after 30 minutes of learning. Total scores can thus range from 0 to 15. Higher scores indicate better memory performance.

Rey Complex Figure Test (RCFT) copy was used to assess participants' visuospatial abilities. Performance is evaluated based on the reproduction of 18 figure elements, each scored on a scale from 0 to 2 (0 = incorrectly placed/absent; 0.5 = inaccurately drawn/incorrectly placed but recognisable; 1 = accurately drawn but poorly placed/incomplete but correctly placed; 2 = accurately drawn and correctly placed), yielding a maximum raw score of 36. Higher scores reflect better performance.

Rey Complex Figure Test (RCFT) immediate recall was used to assess participants' memory by requiring them to reproduce a complex figure from memory after a short delay. Performance is evaluated based on the reproduction of 18 figure elements, each scored on a scale from 0 to 2 (0 = incorrectly placed/absent; 0.5 = inaccurately drawn/incorrectly placed but recognisable; 1 = accurately drawn but poorly placed/incomplete but correctly placed; 2 = accurately drawn and correctly placed), yielding a maximum raw score of 36. Higher scores reflect better performance.

The Information subtest of the Wechsler Adult Intelligence Scale (WAIS) was used to assess participants' verbal comprehension. The subtest comprises 26 dichotomously scored questions (0 = incorrect; 1 = correct), with a maximum raw score of 26. Higher scores indicate better performance.

The Similarities subtest of the Wechsler Adult Intelligence Scale (WAIS) was used to assess participants' verbal reasoning. Consisting of 18 pairs of words, for which participants are asked to describe how the items are similar, responses are scored on a 3-point scale (0 = incorrect; 1 = functional/concrete; 2 = abstract). Raw scores range from 0 to 36, with higher scores indicating better performance.

The Block Design subtest of the Wechsler Adult Intelligence Scale (WAIS) assesses participants' visuospatial abilities. Performance is scored based on the accuracy and speed in reproducing geometric patterns. While the first few items are simple and scored on a 2-point scale (0 = inaccurate; 2 = accurate), later items become more complex and thus yield higher scores (ranging from 0 to 7 depending on the speed of completion). Total scores range from 0 to 66, where higher scores indicate better performance.

The Digit Span subtest of the Wechsler Adult Intelligence Scale (WAIS) was administered to assess participants' working memory and attention. Participants repeated digit sequences of increasing length, with each trial scored as correct or incorrect. The span length of digits to be recalled ranged from 2 to 9 for the forward and sequencing conditions and from 2 to 8 for the backward condition. Total scores range from 0 to 48, with higher scores indicating better performance.

The Coding subtest of the Wechsler Adult Intelligence Scale (WAIS) was used to assess processing speed. Within a 120-second time limit, participants are required to transcribe symbols paired with digits as quickly and accurately as possible. Performance is scored as the number of correctly completed symbols (0 = incorrect; 1 = correct), with higher scores indicating better performance.

The Arithmetic subtest of the Wechsler Adult Intelligence Scale (WAIS) was administered to assess working memory and processing speed. Participants solved 22 orally presented arithmetic problems. Performance was scored as the number of correct answers, with one point awarded per correct item (minimum = 0; maximum = 22). Higher scores indicate better performance.

The Matrix Reasoning subtest of the Wechsler Adult Intelligence Scale (WAIS) was used to assess logical thinking. Comprising 26 items of increasing difficulty, participants identify patterns and select the correct missing piece from several response options. Responses are scored dichotomously (0 = incorrect; 1 = correct), yielding a total score ranging from 0 to 26. Higher scores indicate better performance.

The Trail Making Test A (TMT-A) was administered to assess attention and processing speed. Performance is measured by the time required to sequentially connect numbered dots in ascending order, with longer completion times indicating worse performance.

The Trail Making Test B (TMT-B) was administered to assess executive functioning. Performance is measured by the time required to connect numbered and lettered dots in an alternating ascending order, with longer completion times indicating worse performance.

Presence of parkinsonism was determined based on clinical interviews with participants. Responses were coded as present/absent/unknown for parkinsonism symptoms.

The Unified Parkinson's Disease Rating Scale Part III (UPDRS-III) was administered to assess the presence and severity of parkinsonian motor symptoms. The scale comprises 33 items rated on a 5-point scale (0 = normal to 4 = severe), with higher scores indicating greater motor impairment (minimum = 0; maximum = 132).

The presence of visual hallucinations was assessed based on clinical interviews. Responses were coded as either present/absent/unknown.

The Neuropsychiatric Inventory (NPI) was used to assess the presence of visual hallucinations. Responses were evaluated across three stages: presence, frequency, and severity. Presence of visual hallucinations was coded dichotomously as "Yes" or "No". Frequency was rated on a 4-point scale ranging from 1 (occasionally) to 4 (very frequently), whereas severity was rated on a 3-point scale ranging from 1 (mild) to 3 (severe). Domain scores were calculated by multiplying frequency and severity scores, resulting in a total score ranging from 0 to 12. Higher scores indicate greater impairment from visual hallucinations.

Clinical interviews were used to assess the presence of cognitive fluctuations. Responses were coded as present/absent/unknown.

The Mayo Fluctuations Scale was administered to assess cognitive fluctuations. The scale comprises four dichotomous questions (0 = no; 1 = yes), with total scores ranging from 0 to 4. Higher scores thus indicate greater impairment.

Clinical interviews were used to assess the presence of REM Sleep Behaviour Disorder (RBD). Responses were coded as present/absent/unknown.

The Mayo Sleep Questionnaire is a 16-item instrument used to assess the presence of REM Sleep Behaviour Disorder (RBD). Items are answered dichotomously (0 = no; 1 = yes). The likelihood of RBD is estimated by summing the "yes" responses to the four key RBD sub-questions, yielding a total score ranging from 0 (low likelihood of RBD) to 4 (high likelihood of RBD).

Polysomnography was used to assess the presence of REM Sleep Behaviour Disorder (RBD) according to standard clinical assessment. Polysomnographic findings were coded as present/absent/unknown for the diagnosis of RBD.