About

Joshua J. Fenton, M.D., M.P.H., is a professor and Vice Chair of Research in the Department of Family and Community Medicine at UC Davis Health. His clinical practice focuses on providing primary care for adults and children, with expertise in general family medicine, adult internal medicine, geriatrics, preventive medicine, and mental health and substance use. He speaks Spanish and is dedicated to delivering personal, conscientious healthcare grounded in the latest medical knowledge. His research concentrates on screening, prevention, patient-doctor communication, and enhancing the value and safety of primary healthcare. Dr. Fenton's academic interests include exploring innovative approaches to improve healthcare delivery and patient outcomes. He has received multiple awards for his clinical excellence and research contributions, and his work has significantly contributed to understanding opioid dose tapering, cancer screening, and patient-centered communication in primary care settings.

Research topics

• Medicine
• Internal medicine
• Anesthesia
• Family medicine
• Emergency medicine
• Psychiatry
• Environmental health

Selected publications

• Clar-Friesova skrivnost

  Repository of the University of Primorsk (University of Primorska) · 2026-01-12

  articleOpen access1st authorCorresponding

  A fullerene is a 3-regular plane graph whose faces are hexagons and pentagons. The Fries number of a fullerene is the largest number of benzene rings over all possible Kekulé structures while the Clar number of a fullerene is the largest number of independent benzene rings over all possible Kekulé structures. One question was whether it is always the case that a largest set of independent benzene rings, giving the Clar number, must be a subset of some largest set of benzene rings giving the Fries number. This question is still open for benzenoids, but was answered negatively for fullerenes, with the first counterexample given in paper from E. J. Hartung in 2014. In 2016 in paper from J. E. Graver and E. J. Hartung, the authors constructed a family of fullerenes with the property that the set of benzene rings giving the Clar number was actually disjoint from the set of benzene rings giving the Fries number. Fowler and Myrvold then developed a program for computing the Clar number directly and discovered a significant number of fullerenes in which the Clar sets were not a subset of any Fries set and most of these were not of the type constructed in paper from J. E. Graver and E. J. Hartung in 2016. Exactly why this occurs is somewhat of a mystery. In her Ph.D. thesis, Hartung developed the concept of Clar chains to describe the Kekulé structure giving the Clar sets

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• "It's Part of Dialysis": Lived Experiences of Transportation Challenges Among Patients and Staff in In-Center Hemodialysis.

  PubMed · 2026-02-02

  article

  Transportation insecurity significantly affects dialysis care, yet little research examines its impact from both patient and provider perspectives. This qualitative study explored how transportation challenges influence the experiences of patients receiving in-center hemodialysis and dialysis clinic staff. We conducted 78 semi-structured interviews with patients (n = 49) and staff (n = 29) across four Northern California dialysis clinics. Participants described challenges of navigating two systems, healthcare and transportation, and how this creates emotional distress for patients and staff, disrupts clinic workflows, and compromises treatment adherence. Transportation services are a major part of the patient and staff experience in dialysis clinics. Our findings highlight the need to improve transportation for dialysis patients through collaboration between healthcare systems, transportation providers, and community stakeholders.

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• “It’s Part of Dialysis”: Lived Experiences of Transportation Challenges Among Patients and Staff in In-Center Hemodialysis

  PubMed Central · 2026-02-02

  articleOpen access
  Publisher

• Rebuilding the foundation: recommendations from the Summit to Revitalize Primary Care (Rev PC)

  BMC Proceedings · 2026-03-01

  articleOpen access

  In 2021, an ad hoc committee of the United States (U.S.) National Academies of Science, Engineering, and Medicine (NASEM) affirmed that robust, relationship-centered primary care is the foundation of efficient, effective health care. Yet the ad hoc committee also noted primary care was "slowly dying," due to chronic under-investment, ill-suited payment models, and inadequate workforce planning and development. Encouragingly, efforts to revitalize primary care are underway. To accelerate this movement by generating expert consensus recommendations on the highest priority actions to take in repairing the frayed U.S. primary care base, clinical scientists at the University of California Davis (UCD) School of Medicine convened the Summit to Revitalize Primary Care (Rev PC). Summit recommendations were generated in four closed working sessions of a national Expert Committee. Committee members were selected to ensure a breadth of perspectives (e.g., health plans, purchasers of insurance, regulatory agencies, health systems, clinicians, educators, researchers, economists) from the public and private sectors. Seven high priority recommendations emerged: (1) Increase the proportion of spending on primary care, coupled with initiatives to slow the growth in total health care spending; (2) Pay for primary care using models that support high quality, team-based, relationship-centered, equitable care; (3) Assist practices in transformation to advanced primary care models and assess the impacts on clinical teams, patients, and communities; (4) Maximize primary care's potential to equitably advance health; (5) Advocate for training an appropriately large and diverse primary care physician workforce; (6) Expand research to address the most pressing issues in primary care; (7) Collaborate with a broad array of societal stakeholders in messaging the importance of robust primary care. These recommendations both overlap with and expand on those of the NASEM ad hoc committee and subsequent Standing Committee on Primary Care. Broad pursuit of the recommendations would catalyze sustained momentum toward appropriate primary care investment and workforce planning and development, enabling U.S. primary care to realize its yet-unfulfilled potential to improve population health and advance health equity while helping to control growth in total health care costs.

  PublisherOA PDFDOI

• Facilitators and barriers to deferring imaging for acute low back pain: a qualitative study

  BMC Primary Care · 2025-07-02

  articleOpen accessSenior author

  BACKGROUND: Early imaging for uncomplicated acute low back pain has no diagnostic benefit yet is completed after nearly one-quarter of primary care visits for acute back pain. This qualitative study examined patient and clinician perspectives on facilitators and barriers to deferring imaging for acute low back pain, including potential messages regarding a watchful waiting strategy without early imaging. METHODS: Qualitative data derived from six patient focus groups (N = 30 patients with recent visits for acute low back pain) in Sacramento, CA and nine semi-structured physician interviews in 2020. Patients were asked about expectations regarding imaging, perceptions of care received for acute low back pain, and perspectives about potential messages encouraging a watchful waiting approach without early imaging. Clinicians were asked about facilitators and barriers to deferring low-value imaging. We used thematic analysis guided by grounded theory to identify and integrate themes. RESULTS: Over half of patients had received early imaging during their recent back pain episode. Patients expected physicians to provide a detailed rationale for ordering imaging or not. Patients were typically not persuaded by information on potential harms of imaging and sometimes thought discussion of imaging harms would undermine their trust in the clinician. Patients would be more willing to defer imaging if provided detailed and empathic guidance on pain management. Physicians expressed confidence in advocating a watchful waiting approach without imaging but acknowledged challenges in building patient trust during time-pressed visits, particularly when seeing patients for the first time. CONCLUSIONS: This qualitative study highlights several challenges to deferring early imaging in acute low back pain, as patients typically expect early imaging and were skeptical of clinician messaging about imaging harms. Physicians highlighted lack of a previously established, trustful relationship as a common structural barrier to deferring low-value spinal imaging.

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• Unsupervised machine learning identifies opioid taper reversal patterns in a longitudinal cohort (2008–2018)

  PLOS Digital Health · 2025-04-07 · 2 citations

  articleOpen access

  Chronic pain is commonly treated with long-term opioid therapy, but rapid opioid dose tapering has been associated with increased adverse events. Little is known about heterogeneity in the population of patients on high dose opioids and their response to different treatments. Our aim was to examine opioid dose management and other patient characteristics in a longitudinal, clinically diverse, national population of opioid dependent patients. We used spectral clustering, an unsupervised artificial intelligence (AI) approach, to identify patients in a national claims data warehouse who were on an opioid dose tapering regimen from 2008-2018. Due to the size and heterogeneity of our cohort, we did not impose any restrictions on the kind or number of clusters to be identified in the data. Of 113,618 patients with 12 consecutive months at a stable mean opioid dose of ≥ 50 morphine milligram equivalents, 30,932 had one tapering period that began at the first 60-day period with ≥ 15% reduction in average daily dose across overlapping 60-day windows through 7 months of follow-up. We identified 10 clusters that were similar in baseline characteristics but differed markedly in the magnitude, velocity, duration, and endpoint of tapering. A cluster comprising 42% of the sample, characterised by moderately rapid, steady tapering, often (73%) to a final dose of zero, had excess drug-related events, mental health events, and deaths, compared with a cluster comprising 55% of the sample, characterised by slow, steady tapering. Four clusters demonstrated tapers of various velocities followed by complete or nearly complete reversal, with combined drug-related event rates close to that of the slowest tapering cluster. Unsupervised AI methods, such as spectral clustering, are powerful to identify clinically meaningful patterns in opioid prescribing data and to highlight salient subpopulation characteristics for designing safe tapering protocols. They are especially useful for identifying rare events in large data. Our findings highlight the importance of considering tapering velocity along with duration and final dose and should stimulate research to understand the causes and consequences of taper reversals in the context of patient-centered care.

  PublisherDOI

• Transportation Insecurity and Outcomes in Hemodialysis Patients

  Clinical Journal of the American Society of Nephrology · 2025-06-13 · 8 citations

  articleOpen accessSenior author

  Key Points Transportation insecurity is a potentially modifiable social risk that can negatively impact individuals with ESKD treated with in-center dialysis. Adults with ESKD who lacked private transportation to dialysis were more likely to miss dialysis treatments and had higher mortality. Identifying transportation insecurity and developing novel transportation interventions has potential to improve dialysis adherence and outcomes. Background Transportation insecurity for people with ESKD treated with in-center hemodialysis may be a modifiable social risk that if addressed could improve access to dialysis treatments and lower mortality and complications associated with ESKD. Methods A retrospective, national cohort study between April 1, 2022, and March 31, 2023. The study included all adults with ESKD receiving in-center hemodialysis within a large dialysis organization for at least 90 days before April 1, 2022, and having completed at least one transportation assessment. Primary outcomes were missed dialysis treatments and mortality. Primary exposure was the mode of transportation to dialysis. Results In this study, 115,982 individuals (mean age 63 years, 43% female, 74% residing in urban setting) met the inclusion criteria. Nearly one third (27%) did not have private transportation, defined as driving themselves or having a friend or family member drive them to dialysis. All individuals who lacked private transportation had higher mortality at 1-year follow-up compared with those with private transportation: adjusted incidence rate ratio (aIRRs) (95% confidence intervals [CIs]), 1.25 (1.19 to 1.30), 1.21 (1.15 to 1.28), 1.70 (1.55 to 1.86), and 1.09 (1.02 to 1.17) for Medicaid, paratransit (available for individuals with a disability or a disabling health condition), private pay nonemergency medical transportation, and public transit, respectively. Medicaid, paratransit, and public transportation users were more likely to miss dialysis treatments compared with those with a private ride: aIRRs (95% CIs), 1.31 (1.27 to 1.35), 1.15 (1.11 to 1.20), and 1.24 (1.18 to 1.30), respectively. All nonprivate transportation users had higher likelihood of missed dialysis treatments attributed to transportation: aIRRs (95% CIs), 2.78 (2.62 to 2.94), 2.55 (2.35 to 2.76), 1.83 (1.58 to 2.12), and 2.73 (2.47 to 3.01) for Medicaid, paratransit, private pay nonemergency medical transportation, and public transit, respectively. Conclusions A lack of private transportation was associated with higher risk of missed dialysis treatments and mortality in adults with ESKD treated with in-center hemodialysis.

  PublisherDOI

• Music intervention associated with improved quality of life in patients with breast cancer after mastectomy

  Evidence-Based Nursing · 2025-01-13

  articleSenior authorCorresponding
  PublisherDOI

• Association Between Transportation and Home Dialysis Transition: Retrospective Cohort Study

  Kidney Medicine · 2025-12-11

  articleOpen accessSenior author

  Rationale & Objective: Transportation insecurity is a social risk factor of particular importance to individuals with end-stage kidney disease (ESKD), as most individuals need to travel multiple times a week to dialysis treatment. Advancing home modalities for individuals with ESKD experiencing transportation insecurity may be beneficial by reducing travel burden and improving access. Study Design: Retrospective cohort study. Setting & Participants: Individuals with ESKD treated with in-center hemodialysis (HD) at a large, national dialysis organization. Exposures: The main transportation mode to HD is categorized into private transportation (individuals who drive themselves or have a family member/friend drive) or those who lack private transportation (Medicaid non-emergency medical transportation, paratransit, public transportation, private pay non-emergency medical transportation, and other). Outcomes: Transition to home dialysis is defined as an individual who has completed at least 1 training treatment for home therapies or at least 1 dialysis treatment at home. Analytic Approach: Log-binomial multivariate regression models to estimate adjusted incidence rate ratios of home dialysis transition by transportation mode. Results: < 0.001) among paratransit users. Limitations: Single transportation assessment, exclusion of individuals already on home dialysis, and absence of caregiver data. Conclusions: Individuals with ESKD receiving in-center HD who lack private transportation may have reduced access to home dialysis, even though this group may benefit from home modalities. Better identifying transportation barriers and targeting home modalities for those with transportation insecurity may reduce the adverse consequences of missed dialysis related to transportation barriers and be an additional opportunity to increase home dialysis uptake.

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• Predictors of Incident Benzodiazepine Co-prescription Among Patients Prescribed Long-term Opioids

  Journal of General Internal Medicine · 2025-07-16

  articleOpen accessSenior author

  BACKGROUND: Opioid and benzodiazepine co-prescription is associated with overdose, particularly among patients prescribed long-term opioids. OBJECTIVES: Identify predictors of incident benzodiazepine and opioid co-prescription using two separate and complementary large-scale patient cohorts. DESIGN: Two retrospective cohort studies: (a) statewide dataset based on California's prescription drug monitoring program (PDMP, 7/1/2016-12/1/2018) and (b) national sample of commercial and Medicare Advantage enrollees from the Optum Labs Data Warehouse (OLDW, 7/1/2016-12/1/2021). PARTICIPANTS: Patients prescribed long-term opioids, with opioid coverage for ≥ 80% (≥ 144 days) of a 180-day baseline period absent baseline benzodiazepine or buprenorphine prescriptions. OLDW cohort excluded patients without continuous enrollment, with cancer diagnoses or use of hospice or prolonged inpatient skilled nursing care. MAIN MEASURES: Incident benzodiazepine and opioid co-prescription (≥ 20 days of co-prescription during any 30-day period). KEY RESULTS: Of 617,946 and 223,885 patients, incidence rates of co-prescription were 4.6 and 3.9 cases per 1000 patient-months in the PDMP and OLDW cohorts, respectively. Important predictors included patients prescribed > 150 mg morphine equivalents daily during baseline (PDMP, adjusted hazard ratio: 1.74 [95% CI: 1.67-1.81]; OLDW: 2.66 [2.47-2.86]), and initiated buprenorphine indicated for treatment of opioid use disorder, with (PDMP: 1.68 [1.49-1.89]; OLDW: 2.10 [1.71-2.59]) or without continued treatment (PDMP: 1.35 [1.18-1.56]; OLDW: 1.64 [1.27-2.11]). Co-prescription was positively associated with short-term (60-day) decreases in opioid dose (PDMP: 1.07 [1.04-1.10]; OLDW: 1.06 [1.01-1.12]) but negatively associated with long-term (180-day) decreases (PDMP: 0.81 [0.78-0.85]; OLDW: 0.78 [0.73-0.84]). Patients with anxiety diagnoses were at elevated risk for co-prescription (OLDW: 2.16 [2.06-2.27]), although risk was lower if accompanied by treatment with serotonergic anxiolytics (0.63 [0.59-0.67]). CONCLUSIONS: High baseline opioid dose, buprenorphine initiation, short-term decrease in opioid dose, and anxiety without prescriptions for serotonergic anxiolytics were positively associated with co-prescription. A longer-term decrease in opioid dose and anxiety treated with serotonergic anxiolytics were negatively associated with co-prescription.

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Recent grants

• NIH Grant R21CA158510

  NIH · $390k · 2014

Frequent coauthors

• Joann G. Elmore

  University of California, Los Angeles

  266 shared

• Patricia A. Carney

  Oregon Health & Science University

  255 shared

• William E. Barlow

  Fred Hutch Cancer Center

  247 shared

• Stephen H. Taplin

  247 shared

• Linn Abraham

  Kaiser Permanente Washington Health Research Institute

  246 shared

• Gary Cutter

  University of Alabama at Birmingham

  146 shared

• Edward A. Sickles

  University of California, San Francisco

  146 shared

• Eric A. Berns

  145 shared

Education

• MPH, Health Services

  University of Washington

  2004

• MD, School of Medicine

  University of California San Francisco

  1996

• BA, English

  University of California, Berkeley

  1990

Awards & honors

• Joan Oettinger Memorial Award, UC Davis School of Medicine,…
• Distinguished Research Paper, Society of Teachers of Family…
• Julius R. Krevans Award for Clinical Excellence, San Francis…
• Robert H. Crede Award, UC San Francisco School of Medicine,…