The Relationship between Parkinson’s Disease Symptom Side-of-Onset, Performance on the Unified Parkinson’s Disease Rating Scale Part IV: Motor Complications, and Environmental Exposures Open Access

Bay, Allison (Spring 2018)

Permanent URL:


Abstract: Parkinson’s disease (PD) is a neurodegenerative condition associated with aging and is characterized by loss of dopamine-producing neurons in the substantia nigra pars compacta and a reduction in dopamine levels in the striatum. PD is commonly treated using dopamine-replacement medication called levodopa. Unfortunately, levodopa has decreasing efficacy over time. Periods when levodopa is not effective at controlling symptoms of PD are called “OFF time” or “medication-related motor fluctuations,” (MRMF). One characteristic of PD is unilateral side of symptom onset. Little is known about the differences in left and right onset PD in relationship to response to levodopa treatment; however previous studies have found that side of onset was associated with differential motor and cognitive PD-related symptoms. For example, those with right side onset have faster disease progression than those with left side onset.

Purpose: The objective for this study was to examine differences in MRMF and environmental exposures between left and right onset PD in 64 individuals with mild-moderate PD (age: M(SD)= 68.72 (8.88), years with PD: M(SD)= 6.61 (5.05); Hoehn and Yahr stage Med (1st, 3rd quartile)= 2.0 (2.0, 3.0)).

Methods: We conducted two-tailed independent sample t-tests to examine the differences on the Movement Disorders Society Unified Parkinson disease rating scale (MDS-UPDRS) scores between PD patients with left versus right onset. We then looked at the biserial point correlation and odds of several environmental exposures between right and left onset patients. Finally, we created a logistic regression model to try to examine the ability of environmental exposures to predict side of onset.

Results: Right onset PD was significantly associated with more OFF time (p=0.04), greater impact of motor fluctuations (p=0.02) and more complex MRMF (p=0.01), implying people with right onset PD may have more complications with levodopa treatment. Additionally, we found occupational pesticide exposure to be significantly associated with right onset PD (OR=0.267, CI= 0.072, 0.995) and that pesticide exposures through occupational and proxy (well water, living on a military base) sources were significantly associated with more severe motor symptoms of PD.

Conclusions: Pesticide exposure may be associated with more severe motor symptoms of PD. Alternative and/or adjuvant treatments to alleviate motor symptoms of PD may be particularly beneficial for controlling PD symptoms for those with right onset PD. 

Table of Contents


Table of Contents

















Appendix A (Environmental Exposures Questionnaire)_________________________________19




            Table 1: Pharmaceutical Treatments for PD________________________________________­­__________20


        Table 2: Participant Characteristics _________________________________________21


       Table 3: MDS-UPDRS sum scores by Side of Onset______________________________22


      Table 4: MDS-UPDRS Part IV Items by Side of Onset____________________________22

       Table 5: Side of Onset and Environmental Exposure Factors______________________23 


       Table 6: Biserial Correlations, MDS-UPDRS Sum Scores and Environmental Exposures_24


        Table 7: Correlations between UPDRS: IV Items and Environmental Exposures_______25

        Table 8: Logistic Regression Model for Predicting Right Side of Onset

by Environmental Exposure Status_____________________________________________26



About this Master's Thesis

Rights statement
  • Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.
  • English
Research Field
Committee Chair / Thesis Advisor
Committee Members
Partnering Agencies
Last modified

Primary PDF

Supplemental Files