Objective: This study investigated the effects of subjective vertical position, which a PD patient subjectively perceives as the vertical position, in exacerbating forward flexion posture when standing still.

Background: Although various factors are known to cause postural abnormalities in Parkinson’s disease (PD), very few reports have focused on the integrated abnormality of proprioception.

Method: In patients who consented to the study between September 2019 and March 2021, a one-year prospective observational study was conducted. Posture evaluation included the forward flexion of the trunk (FFT) angle and the lateral flexion of the trunk (LFT) angle when standing still immediately after standing up, as well as the subjective vertical position (SV angle), which the patients subjectively perceive as the vertical position. Measurements were made at initial observation, after 6 months, and after 12 months. The association between the initial SV angle and the FFT angle after 6 months and 12 months, as well as factors that affect the FFT angle after 12 months, were analyzed.

Results: As of October 2021, 140 patients from 13 institutions (mean age, 71.4 years; 64 men and 76 women; mean duration of illness, 67 months; Hoehn-Yahr severity, 2.4; levodopa dose, 398 mg/day; percentage of patients taking a dopamine agonist, 52%) were enrolled in the study. In the analysis of 101 patients who could be observed for 12 months, the initial FFT angle was 11.8±8.5 degrees, and the initial LFT angle was 3.9±3.9 degrees, with no significant changes during observation; however, the SV angle worsened significantly by 2.3 degrees (P=0.002) after 6 months. The initial SV angle was significantly correlated with the FFT angle after 12 months (r=0.68, P=0.001), but it was not correlated with the LFT angle after 12 months. The initial SV angle (P=0.005) and the FFT angle after 6 months (P=0.0001) were identified as factors that affect the FFT angle after 12 months, based on hierarchical multiple regression analysis, adjusted for age, sex, and dopamine agonist use.

Conclusion: The SV angle appears to be useful for predicting FFT angle progression and could show a different trend from clinical assessment items other than posture. The changes in the SV angle over time require further investigation.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/effect-of-perception-of-vertical-position-on-forward-flexion-posture-in-patients-with-parkinsons-disease-a-multicenter-observational-study-interim-report/