Objective: To analyze racial and ethnic disparities and to identify perceived effective strategies for patient recruitment and retention at Parkinson Study Group (PSG) sites.

Background: Many racial and ethnic groups remain underrepresented in Parkinson’s disease (PD) clinical research, limiting the generalizability of observational and interventional data.

Method: Based on existing literature, we created a questionnaire assessing the study participant race and ethnicities, surrounding community demographics, and strategies employed to increase recruitment and retention of underrepresented populations. This survey was distributed to research staff at North American PSG study sites. We used US Census race and ethnicity categorizations.

We used responses to estimate inclusion of racial and ethnic groups in PSG study populations compared to each site’s reported local demographics. Additionally, we identified strategies that site staff found most helpful for increasing recruitment and retention of underrepresented groups.

Results: 40 staff responded to the survey. We calculated a disparity score for seven ethnic groups by dividing the research participant population percentage by local population percentage and subtracting 1 so that a score of 0 indicates proportional representation. This allowed us to have a negative value for underrepresentation and positive value for overrepresentation. Black, Hispanic or Latino, and Asian patients showed the highest underrepresentation (mean disparity scores -5.71, -4.94, -2.56, respectively). White patients were overrepresented (+12.02). 

Responders reported that provision of bilingual study materials and staff, and staff dedicated to recruitment and retention as the most helpful strategies. There was no clear correlation between strategies employed and the calculated disparity score.

Conclusion: These survey data, which capture the perceptions of research staff at PSG sites, highlight ongoing racial and ethnic disparities in PD research trials recruitment. However, responses also suggest effective strategies for reducing these disparities. Future systematic interrogation of these strategies and quantitative investigation of their impact will help reduce the racial and ethnic underrepresentation that continues to challenge PD research.

Enrollment disparity per race.

Helpfulness Score for Outreach Strategy

References: National Academies of Sciences, Engineering, and Medicine; Policy and Global Affairs; Committee on Women in Science, Engineering, and Medicine; Committee on Improving the Representation of Women and Underrepresented Minorities in Clinical Trials and Research; Bibbins-Domingo K, Helman A, editors. Improving Representation in Clinical Trials and Research: Building Research Equity for Women and Underrepresented Groups. Washington (DC): National Academies Press (US); 2022 May 17. 2, Why Diverse Representation in Clinical Research Matters and the Current State of Representation within the Clinical Research Ecosystem. Available from: https://www.ncbi.nlm.nih.gov/books/NBK584396/

Ison JM, Jackson JD, Hemley H, Willis A, Siddiqi B, Macklin EA, Ulysse C, Fitts MS, Pham TT, Afshari M, Agarwal P, Aminoff M, Bissonnette S, Fullard M, Khan TS, Larson DN, Wielinski C, Sanchez AV. Fostering Inclusivity in Research Engagement for Underrepresented Populations in Parkinson’s Disease: The FIRE-UP PD study. Contemp Clin Trials. 2024 Sep;144:107619. doi: 10.1016/j.cct.2024.107619. Epub 2024 Jul 5. PMID: 38971301.

U.S. Census Bureau, “DP1 PROFILE OF GENERAL POPULATION AND HOUSING CHARACTERISTICS,” 2020, , accessed on April 10, 2025.

Office of Management and Budget. (2023). OMB bulletin 23-01: Revised delineations of metropolitan statistical areas [PDF]. Retrieved from https://www.bls.gov/bls/omb-bulletin-23-01-revised-delineations-of-metropolitan-statistical-areas.pdf

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MDS Abstracts - https://www.mdsabstracts.org/abstract/analyzing-perceived-effectiveness-of-implemented-recruitment-and-retention-strategies-for-underrepresented-racial-and-ethnic-groups-in-parkinsons-disease-clinical-trials/