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Characterizing a Cohort of Parkinson's Disease Patients and Controls in a Peripheral Biomarker Development Study

Education and Research Strategies
  • Primary Categories:
    • Clinical-Adult
  • Secondary Categories:
    • Clinical-Adult & Pediatric
Introduction:
Despite the success of biomarker research in other neurodegenerative diseases, Parkinson’s disease (PD) has remained challenging for biomarker development.  As a result, patients with early signs of PD may experience delays in diagnosis and treatment. Researchers at the HudsonAlpha Institute for Biotechnology in Huntsville, AL, have previously identified small RNA signatures in amyotrophic lateral sclerosis (ALS) patients that hold potential for earlier diagnosis and monitoring of disease progression. Building on these findings, microRNA sequencing is now being employed in a local cohort of individuals with PD, with recruitment facilitated through the Smith Family Clinic for Genomic Medicine. Data collection has targeted both environmental and family history data, as PD is considered a multifactorial disorder. Here, we report recruitment data and preliminary outcomes.

Methods:
Participants were recruited through flyers, posters, social media outreach, and community engagement at public events. Individuals of any age with a diagnosis of PD were eligible, and control samples were collected from generally age-matched individuals with or without a family history of PD. Data collected included participant demographics, neurological and other medical history, family history, and information on risk factors and exposures. Participants also completed the University of Pennsylvania Smell Identification Test (UPSIT), a 40-item instrument designed to measure olfactory dysfunction, a common early symptom in PD.

Results:
To date, 102 individuals have enrolled in this study, comprising 44 cases and 58 controls. The mean age of all participants is 71.2 years, with cases averaging 73.8 years (range 56-86) and controls averaging 69.2 years (range 35-87). Cases are skewed more heavily toward males (68%, n= 30), while controls are skewed more heavily toward females (69%, n=40). Age at symptom onset is 67.0 years (range 47-83), with an average age at diagnosis of 69.1 years (range 48-85).

 

Thirty-three cases (75%) had never smoked, while 11 (25%) report former tobacco use; 84% of controls report having never smoked, while 12% report former tobacco use and 3% report current occasional use. Twenty seven percent of cases (n=12) had a history of head injury with loss of consciousness, compared to 21% of controls (n=12); 25% of cases (n=11) had a history of repeated blows to the head, compared to 7% of controls (n=4). Eighteen percent of cases (n=8) report a history of exposure to chemical warfare, while 34% (n=15) report a history of prolonged exposure to industrial pesticides or herbicides. In contrast, no controls reported a history of exposure to chemical warfare, and only 10% (n=6) reported prolonged pesticides or herbicide exposure. Twelve affected individuals report a family history of PD (27%), while another 7 (16%) report a family history of symptoms suspicious for PD. Thirty-one controls reported a family history of PD (53%).

 

Individuals with PD demonstrated significantly lower UPSIT scores (mean 19, range 7–36) compared to controls (mean 32, range 11–39) [p<0.0001 by Mann-Whitney test]. Among cases, 50% (n=22) had 'total anosmia', 23% (n=10) 'severe microsmia', 18% (n=8) 'moderate microsmia', 5% (n=2) 'mild microsmia', and 5% (n=2) 'normosmia'. In contrast, only 7% (n=4) of controls scored in the 'total anosmia' range, 3% (n=2) in 'severe microsmia,' 16% (n=9) in 'moderate microsmia,' 31% (n=18) in 'mild microsmia,' and 43% (n=25) in the 'normosmia' range.

Conclusion:
These findings highlight notable differences in olfactory dysfunction and exposure history between PD cases and controls. The increased rates of anosmia, chemical warfare and pesticide exposure, and head trauma history among cases underscore potential environmental risk factors and early indicators for PD. This work also demonstrates the feasibility of targeted recruitment for biomarker research, laying the groundwork for future studies on genomic risk factors, development of polygenic risk scores, early detection, and progression monitoring for PD.

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