Objective: Our goal was to investigate the rate of progression to dementia (PDD) in our cohort of Parkinson’s disease (PD) patients and to explore how motor features change over time in patients who will convert to PDD.

Background: There seems to be a particular pattern of motor progression in PD that precedes conversion to dementia with gait and posturality disorders clustering with PDD milestone at similar latencies.

Method: In this a prospective cohort study we followed 130 patients for 4 years. At each visit mild cognitive impairment (PD-MCI) and PDD were diagnosed according to Movement Disorders Society task force criteria (level 2 for PD-MCI). Depending on the change in cognitive status over time, a cognitive outcome was determined. Detailed motor measurements were applied, including rigidity, axial, bradykinesia, tremor and postural instability gait disorders (PIGD) scores. Progression rates for each of the motor scores were calculated and compared between dementia converters (PDDc), patients who remain cognitively intact during the follow up (PD-CNs) and patients with PD-MCI throughout the study (PD-MCIs) who did not convert to PDD.

Results: A total of 32 (29.62%) patients became demented during the follow-up period, resulting in an incidence rate of dementia of 102 cases per 1000 person-years in this sample. There was a significant difference in mean progression rates of axial motor score, whilst controlling for age and PD duration, (F(2,62)=7.836, p=0.001) between PD-CNs, PD-MCIs, and PDDc. UPDRS motor scores at the two time points (year1 and year2) and at baseline showed significant interaction (F(1,34)= 6.79 p = 0.013), i.e. the ‘effect’ of time from baseline was different for PD-MCIs and PDDc group – increase by 3.9 units from year 1 to year 2 in PDDc group (53.1 vs 57, p(Bonferroni)=.01, while the scores in PD-MCIs group remained constant (51.5 vs. 48.7, p(Bonferroni)=.18). A large interaction effect was obtained with axial score as a dependent variable (F(1,34)=23.12, p=.001, partial eta squared=.28) with increase by 2.1 units from year 1 to year 2 in PDDc group (7.2 vs. 9.3, p(Bonferroni)<.001, while the scores in PD-MCIs group remained practically the same (6.4 vs. 6.1, p(Bonferroni)=.45).

Conclusion: Conversion to PDD is associated with faster buildup of axial motor symptoms.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-prospective-study-of-parkinsons-disease-progression-towards-dementia-dynamics-and-defining-motor-features/