About

Brandon David Lewis Marshall is the Royce Family Professor of Teaching Excellence in Epidemiology at the Brown University School of Public Health and the Founding Director of the People, Place & Health Collective (PPHC) at Brown University. He received his PhD in epidemiology from the School of Population and Public Health at the University of British Columbia and completed postdoctoral training at Columbia University Mailman School of Public Health. His research broadly focuses on substance use epidemiology, harm reduction, and the social, environmental, and structural determinants of health among drug-using populations. Marshall's work aims to improve the health and well-being of people who use drugs, and he has authored or co-authored over 400 peer-reviewed publications and two book chapters. He is the Principal Investigator of multiple NIH-funded projects, including the Rhode Island Prescription and Injection Drug Use Study (RAPIDS) and PROVIDENT, a randomized trial to prevent overdose deaths. Additionally, he serves as the Scientific Director of PreventOverdoseRI, Rhode Island's drug overdose surveillance dashboard, and as an expert advisor to the Rhode Island Governor's Overdose Prevention and Intervention Task Force. Marshall also serves as an Associate Editor for the International Journal of Drug Policy.

Research topics

• Medicine
• Internal medicine
• Psychiatry
• Environmental health
• Demography
• Emergency medicine
• Medical emergency
• Sociology
• Political Science
• Nursing
• Psychology
• Family medicine
• Pediatrics
• Intensive care medicine
• Virology
• Pharmacology
• Gerontology

Selected publications

• Advancing systems thinking in implementation science: An epidemiologic perspective

  Annals of Epidemiology · 2026-04-15

  article
  PublisherDOI

• Overdose Prevention Centers and Neighborhood Commercial Activity in New York City

  JAMA Network Open · 2026-02-27

  articleOpen access

  Importance: Overdose prevention centers (OPCs) are interventions to reduce overdose mortality and support health care engagement. In the US, concerns have been raised that OPCs may be associated with reduced economic activity in their surrounding neighborhoods. Objective: To evaluate changes in the local economic activity in New York City (NYC), measured by neighborhood-level foot traffic and consumer spending, following the opening of the first 2 publicly recognized OPCs in the US. Design, Setting, and Participants: This cohort study used anonymized mobility and spending data from June 1, 2021, to June 13, 2022, for the areas surrounding the East Harlem and Washington Heights OPCs in NYC. These neighborhoods were defined using 5-minute and 10-minute walking buffers and Business Improvement Districts (BIDs). Synthetic control donors included walking buffers and BIDs around syringe service programs without OPCs and opioid treatment programs that were operational as of OPCs' opening. Analyses were conducted from February to July 2025. Exposures: Opening of the 2 NYC OPCs on November 30, 2021. Main Outcomes and Measures: Primary outcomes were foot traffic and in-person consumer spending within 10-minute walking buffers. Secondary analyses considered 5-minute walking buffers and BIDs. Augmented synthetic control models were adjusted for neighborhood-level demographic and socioeconomic features, with fit assessed using root mean squared error before OPC opening. Permutation tests and conformal inference were used to assess significance. Results: A total of 27 biweekly observations (13 in pre-OPC and 14 in post-OPC periods) were analyzed. The 10-minute walking buffer analyses captured 1259 consumer spending sites and 7816 foot traffic sites across 2 treated buffers and 56 donor buffers. In East Harlem, the average treatment effect on the treated (ATT) estimate (SE) was -$21.96 ($40.53) for consumer spending (P = .16) and 1.28 (5.40) visits for foot traffic (P = .19). In Washington Heights, ATT (SE) estimates were $14.94 ($37.38) for consumer spending (P = .13) and 0.44 (3.54) visits for foot traffic (P = .97). Secondary analyses produced consistent results. No statistically significant results were observed at any post-OPC time point. Conclusions and Relevance: This cohort study found that OPC opening was not associated with significant changes in local economic activity. Given the absence of observed economic harms, policy debates should instead focus on the public health implications of OPCs.

  PublisherOA PDFDOI

• Abstract WP145: Micro-Contextual Factors are Related to Delayed Hospital Arrival: Findings From the Time is Brain Stroke Response Questionnaire

  Stroke · 2026-01-29

  article

  Introduction: Social determinants of health are associated with delayed hospital arrival. However, there is scant evidence on micro-contextual factors that influence arrival delay, especially the role of bystanders and patients’ perceptions of them during prehospital phases. We investigated the association of a series of micro-contextual factors with arrival delay. Methods: In a multicenter observational study, data on in-the-moment factors during symptom onset were prospectively collected from patients with acute stroke syndrome admitted at two tertiary care centers. We assessed bystander characteristics with a novel stroke instrument—the number of bystanders, patients’ perceptions of bystander stroke knowledge, concern about symptoms, trustworthiness, and family status. We aggregated information about each bystander to create separate proportional measures that characterize the micro-contexts during symptom onset. The primary outcome was arrival delay (1 = ≥ 3 hours, 0 < 3 hours). Binary logistic regressions adjusted for age, sex, stroke severity, prior stroke, stroke type, EMS use, home onset, nighttime onset, weekend onset, and hospital distance. Results: We interviewed 280 patients between January 2023 and July 2025 with complete data. Median age was 70 (IQR=55.75-79), 43.9% were female, and median NIHSS was 3 (IQR=1-7). There were 43.9 % of patients with delayed arrival (≥3 hours). The median bystander amount was 2, ranging from 1 to 8. In adjusted regression models, an increasing number of bystanders was associated with a higher likelihood of delay (OR=1.34, 95% CI=1.07-1.68, p=0.0103). Patients with higher proportions of bystanders who were family (OR = 0.38, 95% CI=0.16-0.85, p=0.0200) and trustworthy (OR=0.20, 95% CI=0.09-0.43, p < 0.001) were less likely delayed. There were no significant associations between proportions of bystanders who were perceived as knowledgeable about stroke (OR=0.77, 95% CI=0.38-1.53, p=0.4557) or who were concerned about symptoms (OR=0.50, 95% CI=0.21-1.17, p=0.1113) with delay. Conclusion: We found that micro-contextual factors, particularly the number of bystanders, the presence of family, and the amount of trustworthiness, were associated with delayed arrival, independent of known factors. The proportion knowledgeable about stroke or concerned was not related to delayed arrival. These micro-contextual factors are important because they are potentially modifiable to reduce prehospital delay for acute stroke.

  PublisherDOI

• Impact of COVID-19 on late HIV diagnosis rates by race/ethnicity in Ending the HIV Epidemic (EHE) priority jurisdictions in the United States

  JAIDS Journal of Acquired Immune Deficiency Syndromes · 2026-04-15

  article

  INTRODUCTION: This study aims to determine the effect of the COVID-19 pandemic on changes in late HIV diagnoses by race/ethnicity across Ending the HIV Epidemic (EHE) priority jurisdictions in the US. METHODS: We analyzed annual county- and state-level (when county-level data were unavailable) late HIV diagnosis data in EHE priority jurisdictions from local epidemiological profiles and the AIDSVu between 2017-2022. Descriptive analyses were conducted to examine the percentages of late diagnoses across racial/ethnic groups before and after the onset of the pandemic. We then used interrupted time-series analysis to assess changes in both the level and trend of late diagnosis percentages across non-Hispanic White, non-Hispanic Black, and Hispanic populations. RESULTS: We included a total of 31 jurisdictions. The highest percentages of late HIV diagnoses were more often reported among Black or Hispanic populations. There were statistically significant (P<0.05) downward trends in late diagnosis percentages before the pandemic among the Black population in Kings County, NY(-3.8%), Georgia(-0.8%), and Los Angeles County, CA(-4.5%), and among the Hispanic population in Georgia(-4.9%). Subsequently, there were significant immediate increases in 2020 in the Black population in Kings County, NY(11.5%), Georgia(2.5%), and Los Angeles County, CA(10.8%), and among the Hispanic population in Georgia(11.5%). Additionally, there was a significant annual increase in the trend after the onset of the pandemic in both the Black(1.0%) and Hispanic populations(4.8%) in Georgia. In contrast, no statistically significant changes were found in the White population. CONCLUSIONS: The COVID-19 pandemic appears to have exacerbated existing race/ethnic disparities in late HIV diagnoses among several EHE jurisdictions.

  PublisherDOI

• Abstract HUP7: Significant Difference in Stroke Knowledge by Race: Evidence from the Time is Brain Observational Study

  Stroke · 2026-01-29

  article

  Introduction: Stroke education is a key determinant of timely hospital arrival. While considerable evidence indicates that Black patients experience greater prehospital delay, few studies have investigated whether these gaps extend to stroke knowledge. Methods: Time is Brain is a multicenter, prospective, observational study investigating social, psychological, and demographic determinants of prehospital delay. Demographics, clinical characteristics, and stroke knowledge were collected from patients with acute stroke syndrome presenting to two tertiary care centers in the Northeast. Stroke knowledge was assessed through a validated 19-item stroke knowledge test. A Mann-Whitney U test was performed to compare stroke knowledge scores between Black and White participants of any ethnicity. Rank-based median regression was then used to evaluate the association between race and stroke knowledge while adjusting for sex, age, education level, cognitive status, socioeconomic status (SES), NIH Stroke Scale (NIHSS) and healthcare distrust. Results: A total of 321 patients with acute stroke syndrome were enrolled between January 2023 and July 2025 (mean age = 66.30, SD = 15.64, 43.9% Female, median NIHSS = 2). A total of 60 participants (19%) self-identified as Black and 240 as White (75%). All other racial groups were underpowered for statistical analysis (n&lt;5). Stroke knowledge was non-normal (Shapiro-Wilk p &lt;0.001, skewness=-0.85, kurtosis=0.53). In the unadjusted analysis, Black participants had significantly lower stroke knowledge scores than White participants (median [IQR] 8.5 [6.25-11.0] vs. 11.0 [9.0-13.0], p &lt;0.001). In the adjusted median regression model, Black race was significantly associated with lower stroke knowledge scores (β = -2.35, 95% CI [-3.60, -1.10], p =0.002), independent of sex, age, education level, cognitive status, SES, NIHSS and healthcare distrust. In this model, fewer years of education completed (β = 0.24 [0.07,0.41], p &lt;0.01) and lower cognitive status scores (β = -0.11 [-0.20,-0.02], p =0.020) were also associated with lower stroke knowledge. Conclusion: In this multicenter cohort, Black participants had significantly lower stroke knowledge than White participants, a difference that remained significant when adjusting for demographic, educational, and clinical factors. This difference warrants further investigation into the underlying causes and potential interventions to improve stroke knowledge in Black patients.

  PublisherDOI

• A spatially dynamic agent-based model for assessing the effect of gentrification-induced migration and HIV transmission among heterosexual African American/Black women

  Annals of Epidemiology · 2025-08-19

  articleOpen accessSenior author
  PublisherOA PDFDOI

• A descriptive study of drug overdose epidemics, overdose prevention efforts, and opioid settlement fund distribution across six states

  International Journal of Drug Policy · 2025-12-05

  articleOpen access
  PublisherOA PDFDOI

• Trajectories of neighborhood-level overdose risk predictions for prioritization of harm reduction services: Results from the PROVIDENT study

  Drug and Alcohol Dependence · 2025-10-17

  articleSenior author
  PublisherDOI

• Stemming the Tide of the US Overdose Crisis: How Can We Leverage the Power of Data Science and Artificial Intelligence?

  Milbank Quarterly · 2025-06-04

  articleOpen access

  Policy Points We can leverage data science and artificial intelligence to inform state and local resource allocation for overdose prevention. Data science and artificial intelligence can help us answer four questions: (1) What is the impact of laws on access to interventions and overdose risk? (2) Where should interventions be targeted? (3) Which types of demographic subgroups benefit the most and the least from interventions? and (4) Which types of interventions should they invest in for each setting and population? Advances in data science and artificial intelligence can accelerate the pace at which we can answer these critical questions and help inform an effective overdose prevention response.

  PublisherOA PDFDOI

• On the compounding manifestations of racism shaping the US HIV/AIDS epidemic: why ending the HIV epidemic must address these factors for success

  AIDS · 2025-07-04 · 1 citations

  articleOpen access

  OBJECTIVE: Growing racial/ethnic inequities in healthcare access and racially segregated sexual mixing contribute to persistent disparities in HIV incidence in the US. We aim to examine the extent to which eliminating racial/ethnic inequities in healthcare access could reduce disparities in HIV incidence and its interaction with assortative sexual mixing. DESIGN: A mathematical model. METHODS: We used two independently developed HIV transmission models to estimate HIV incidence among Black, Hispanic/Latino, and White/Other MSM and the corresponding incidence rate ratios (IRRs) comparing Black and Hispanic/Latino to White/Other as a measure of disparity in the four "Ending the HIV Epidemic (EHE)" counties in Georgia. We compared three scenarios: status quo; equal service access across racial/ethnic groups with reported assortative sexual mixing by race/ethnicity; and equal service access with random sexual mixing. We standardized both models to enhance comparability. RESULTS: Under the status quo, both models projected a reduction in overall HIV incidence but persistent racial/ethnic disparities, with an IRR as large as 8.3 between Black and White/Other MSM. Compared to the status quo, providing equal health service access resulted in a modest reduction in IRRs with reported assortative sexual mixing in 2030, but yielded a much greater reduction when sexual mixing was at random: IRR reduced by up to 38.8% and 58.3% between Black and White/Other MSM in the two models. CONCLUSION: This study highlights racially segregated sexual mixing as a barrier to efforts to mitigate racial/ethnic disparities in HIV incidence. Reaching EHE targets will require not only equitable healthcare access but also strategies addressing sexual racism and other structural barriers.

  PublisherOA PDFDOI

Recent grants

• Core C: Translational and Transformative Research

  NIH · $37.8M · 2018–2028

• NIH Grant DP2DA040236

  NIH · $2.4M · 2021

• NIH Grant R21MH109360

  NIH · $459k · 2019

• NIH Grant R03DA037770

  NIH · $335k · 2017

• Reducing Drug-Related Mortality Using Predictive Analytics: A Randomized, Statewide, Community Intervention Trial

  NIH · $3.1M · 2019–2025

Frequent coauthors

• Traci C. Green

  Rhode Island Hospital

  261 shared

• Thomas Kerr

  221 shared

• Evan Wood

  Waypoint Centre for Mental Health Care

  209 shared

• William C. Goedel

  Brown University

  207 shared

• Scott E. Hadland

  Massachusetts General Hospital

  162 shared

• Julio Montaner

  University of British Columbia

  131 shared

• Xiao Zang

  University of Minnesota

  125 shared

• Bohdan Nosyk

  St. Paul's Hospital

  122 shared

Labs

• People, Place & Health Collective (PPHC) at Brown UniversityPI

Education

• PhD, School of Population and Public Health

  University of British Columbia

  2011