Demographic and Clinical Characteristics in Different Motor Subtypes of Parkinson's Disease: How Well Do the Findings Fit Within the Framework of Existing Hypotheses?

Background and purpose: This study aimed to investigate risk factors, prodromal signs, and non-motor symptoms (NMSs) across various motor subtypes of Parkinson's disease (PD) and to interpret the findings within the context of existing hypotheses on PD subtypes.

Methods: A search of the database yielded 300 individuals who satisfied the study's inclusion and exclusion criteria. Among them, 168 patients diagnosed with idiopathic PD underwent a comprehensive evaluation of both motor and non-motor symptoms. The classification of motor subtypes was conducted according to the methodology proposed by Stebbins.

Results: The study population consisted of 59.9% males, with an average age of disease onset at 65.45 years. Among them, 87 (51.8%) were classified as having the tremor-dominant (TD) subtype, 61 (36.3%) had the postural instability and gait disorder (PIGD) subtype, and 20 (11.9%) fell into the intermediate (I) subtype. Significant differences between motor subtypes were observed in age at assessment (p = 0.03), age at onset (p = 0.02), education level (p = 0.015), handedness (p = 0.013), proportion of non-smokers (p = 0.021), cognitive impairment (p = 0.003), and apathy (p = 0.003). Additionally, statistically significant variations were found across different rating scales and questionnaires, including MoCA (p = 0.009), HAM-A (p = 0.008), HAM-D (p = 0.007), H&Y (p = 0.004), SAS (p = 0.004), NMSS Domain 3 (mood/apathy) (p = 0.003), and NMSS Domain 5 (attention/memory) (p = 0.003).

Conclusions: The study revealed substantial differences between motor subtypes, underscoring the complexity of PD. These findings highlight the importance of comprehensive evaluations of both MS and NMSs to optimize patient care, improve quality of life, and fit well within the framework of the existing hypotheses of PD subtypes.