Objective: To determine the effects of motor subtypes’ stability on non-motor symptoms (NMS) over three years in early Parkinson’s disease (PD).

Background: Research have found significant correlations between NMS and PD motor subtypes. However, there is limited literature on motor subtype stability and its relationship with NMS such as anxiety, apathy and depression.

Method: 109 early PD patients from the Early PD Longitudinal Singapore Study (PALS) were split into 3 subtype stability groups: tremor-dominant stable (TD-S; N=51), postural instability and gait difficulty (PIGD-S; N=10), and non-stable (NS; N=48) across 3 years. Motor subtypes were classified according to the Movement Disorder Society’s Unified PD Rating Scale (MDS-UPDRS) criteria. A repeated measures linear model was run to determine the effects of subtype stability on NMS scores of anxiety, apathy, depression, fatigue and sleep while controlling for age, gender, baseline LEDD and MDS-UPDRS III.

Results: There was an overall significant effect of subtype stability on NMS between subjects (λ1=0.136, F(6,98)=2.22, p=0.04) and a significant time and subtype stability interaction effect within subjects (time*subtype: λ1=0.065, F(6, 202)=0.06, p=0.04). Univariate analyses found increasing anxiety levels to be significantly associated with time (F2,204=3.77, p=0.03) across all groups. Apathy levels were also significantly different between groups (F2,102=4.87, p=0.10) across 3 years. Pairwise comparisons after adjustment for multiple comparisons showed significant differences between TD-S and NS in apathy, with TD-S having higher apathy levels than NS (MD: 2.71, p= 0.007).

Conclusion: Increased anxiety levels were found over time across all groups regardless subtype stability. TD-S had significantly higher apathy levels than NS. We postulate that this may be due to learned helplessness as TD-S generally experience lesser fluctuations, which may allow them to feel more indifferent about their condition or less motivated to work toward reducing their disease progression. In contrast, due to its fluctuating nature, the NS group may feel the effects of contributing factors such as medication, exercise and disease progression more drastically. This may allow them to feel more concerned about their progress and more motivated to act on it in hopes to reduce fluctuations. 

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MDS Abstracts - https://www.mdsabstracts.org/abstract/effects-of-motor-subtype-stability-on-non-motor-symptoms-in-early-parkinsons-disease/