- ICD screening positivity was similar in TD-PD and PIGD-PD (21.4% vs 21.2%; OR 1.01, p = 0.970).
- Continuous and categorical normalized QUIP-CS scores did not differ between subtypes (continuous p = 0.674; categorical p = 0.632).
- Sensitivity analyses and Bayesian evidence support the null, suggesting motor-subtype cerebellar differences do not influence ICD symptoms in early PD.
medRxiv [Preprint]. 2026 Sep 8:2026.09.04.26362266. doi: 10.64898/2026.09.04.26362266.
ABSTRACT
OBJECTIVE: Impulse control disorders (ICDs) are clinically important nonmotor features of Parkinson’s disease (PD). Tremor-dominant PD (TD-PD) has been associated with greater cerebello-thalamo-cortical involvement, whereas postural instability/gait difficulty-dominant PD (PIGD-PD) has been linked to more prominent basal ganglia and frontostriatal dysfunction. We therefore examined whether ICD symptoms differ by motor phenotypes.
METHODS: This cross-sectional study analyzed baseline data from the Parkinson’s Precision Medicine Initiative (PPMI). Motor subtype classification was based on Movement Disorder Society-Unified Parkinson’s Disease Rating Scale (MDS-UPDRS) criteria. ICD symptoms were assessed using the Questionnaire for Impulsive-Compulsive Disorders in Parkinson’s Disease-Current Short Form (QUIP-CS) and evaluated across multiple levels of analysis using the standard screening definition and normalized QUIP-CS scores analyzed categorically and continuously. Temporal-alignment, subgroup, multivariable, and Bayesian analyses were performed to assess the robustness of the primary findings.
RESULTS: We analyzed 305 participants (173 TD-PD, 132 PIGD-PD). Screening-defined ICD positivity was similar between subtypes (21.4% vs 21.2%, OR = 1.01, 95% CI 0.58-1.76, p = 0.970). Continuous and categorical normalized QUIP-CS scores likewise did not differ between groups (continuous score: 0.0338 vs 0.0384, p = 0.674; categorical score: 3.5% vs 4.5%, p = 0.632). Temporally aligned, subgroup, and multivariable sensitivity analyses consistently supported the primary finding, and Bayesian analysis provided moderate evidence supporting the null hypothesis (BF 01 = 7.21).
CONCLUSIONS: ICD symptoms do not differ between TD-PD and PIGD-PD motor subtypes in early PD. These findings suggest that motor subtype-associated differences in cerebellar involvement do not substantially influence ICD symptoms in early PD.
PMID:42732189 | PMC:PMC13564804 | DOI:10.64898/2026.09.04.26362266
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