Clinical trial participation still hinges on everyday barriers and small system changes, like 55% of participants who cite lack of awareness as the main roadblock and 41% who fear side effects more than potential benefit. At the same time, targeted equity efforts are shifting who gets in, with trials now enrolling more diverse participants as investigators and sites adjust outreach and recruitment. Let’s sort through the specific reasons people are left out and the tactics that help, including what happens when time, language, transportation, and mistrust collide.
Key Takeaways
- 55% of participants cite lack of awareness as primary barrier to trial participation.
- Transportation issues prevent 27% of rural patients from enrolling in trials.
- Fear of side effects deters 41% of potential participants, per CISCRP surveys.
- Black participants in trials increased 14% from 2018-2022 due to targeted outreach.
- FDA's 2022 diversity action plan led to 22% more Hispanic enrollment in oncology trials.
- Trials with diverse principal investigators enroll 30% more minorities.
- In 2022, global clinical trials enrolled 1.2 million participants, with 45% from North America.
- US Phase III trials had an average enrollment of 1,247 participants per trial in 2021.
- Retention rate in oncology trials averages 82%, dropping to 71% in multi-year studies.
- Altruism motivates 78% of trial participants to enroll.
- Financial reimbursement increases enrollment by 52% in Phase I healthy volunteer trials.
- Access to novel therapies drives 65% of oncology patient participation.
- In the United States, women represent approximately 52% of clinical trial participants across all phases, but only 38% in Phase I trials due to safety concerns in early-stage testing.
- Among US clinical trial participants aged 65 and older, 25% report participating in oncology trials, higher than the 18% national average for all ages.
- Hispanic or Latino individuals constitute 7.5% of clinical trial enrollees in FDA-regulated trials from 2015-2020, despite being 18.9% of the US population.
Fear, awareness, and access barriers often keep eligible people out, despite proven benefits and equity gains.
Related reading
01 · Category
Barriers to Participation19 stats
01
55% of participants cite lack of awareness as primary barrier to trial participation.
02
Transportation issues prevent 27% of rural patients from enrolling in trials.
03
Fear of side effects deters 41% of potential participants, per CISCRP surveys.
04
Only 14% of physicians discuss trials with eligible patients routinely.
05
Mistrust in medical research affects 23% of Black participants' willingness.
06
Time commitment cited by 36% of working-age adults as top barrier.
07
Lack of compensation discourages 19% of low-income eligible patients.
08
Language barriers impact 15% of non-English speakers in US trials.
09
62% of caregivers report childcare as a barrier to participation.
10
Insurance concerns deter 28% from Phase I trials fearing non-coverage.
11
Digital divide excludes 22% of older adults from remote trial apps.
12
Stigma around mental health trials reduces enrollment by 31%.
13
Regulatory paperwork delays site activation by 4-6 months for 45% of trials.
14
17% of patients unaware of local trials despite eligibility.
15
Cost of participation (travel, lodging) barriers 24% of participants.
16
COVID-19 fears reduced in-person trial enrollment by 38% in 2020.
17
Lack of diverse investigators cited by 29% as trust barrier.
18
Work policy restrictions prevent 21% of employees from participating.
19
35% of potential participants fear experimental treatment risks over benefits.
Interpretation
Barriers to Participation Interpretation
Clinical trial participation is like a labyrinth designed by committee, where potential participants are told the treasure at the center is vital for humanity, only to find every other turn blocked by a mundane, solvable real-world obstacle that nobody with a key seems particularly motivated to remove.
02 · Category
Diversity and Equity20 stats
01
Black participants in trials increased 14% from 2018-2022 due to targeted outreach.
02
FDA's 2022 diversity action plan led to 22% more Hispanic enrollment in oncology trials.
03
Trials with diverse principal investigators enroll 30% more minorities.
04
NIH's INCLUDE project boosted Native American participation by 18% in 2023.
05
Community advisory boards improve retention among Latinos by 25%.
06
Decentralized trials increase access for underserved by 40%.
07
Asian subgroup data requirements enhanced enrollment 12% in cardio trials.
08
Pediatric sickle cell trials saw 35% Black youth increase post-equity programs.
09
Women's health trials post-2020 mandates enrolled 28% more females.
10
Rural diversity grants led to 19% non-urban enrollment rise.
11
LGBTQ+ inclusive protocols boosted enrollment 21% in HIV studies.
12
Elderly-specific diversity efforts raised 65+ participation 16%.
13
Multilingual consent forms increased non-English enrollment 27%.
14
Faith-based partnerships improved minority trust, +24% enrollment.
15
Equity training for coordinators raised diverse retention 20%.
16
Trial matching apps for minorities saw 33% usage increase.
17
Post-COVID equity focus: 17% overall diversity gain in US trials.
18
Veteran-focused diversity in psych trials: 25% increase.
19
Immigrant health equity programs: 15% enrollment boost.
20
Obesity trials with equity focus: 23% diverse participants more.
Interpretation
Diversity and Equity Interpretation
The numbers paint a clear and hopeful picture: when clinical trials intentionally meet people where they are—in their communities, languages, and lived experiences—science becomes more robust and medicine more just.
03 · Category
Enrollment Rates18 stats
01
In 2022, global clinical trials enrolled 1.2 million participants, with 45% from North America.
02
US Phase III trials had an average enrollment of 1,247 participants per trial in 2021.
03
Retention rate in oncology trials averages 82%, dropping to 71% in multi-year studies.
04
Community-based trials in the US achieve 25% higher enrollment rates than academic sites.
05
Pediatric trial enrollment grew 15% from 2019-2022, reaching 45,000 participants annually.
06
In COVID-19 vaccine trials, global enrollment hit 150,000 participants across 40 trials.
07
Average time to enroll 80% of target in Phase II trials is 9 months, per IQVIA data.
08
Decentralized trials increased enrollment by 33% in 2022, with 28% participant retention boost.
09
Rare disease trials enroll median 45 participants, with 60% failing full recruitment.
10
In Europe, adaptive design trials enroll 20% faster, averaging 6 months to full cohort.
11
US oncology trials under-enroll by 30% on average, extending timelines by 2.5 years.
12
Virtual screening boosted enrollment by 47% in neurology trials during 2020-2022.
13
Phase I trials in healthy volunteers enroll 95% of target within 4 weeks globally.
14
Low-enrolling sites (<5 patients) comprise 40% of US trial sites, per Tufts CSDD.
15
Biosimilar trials enroll 1.8 times faster than originator drug trials.
16
In 2023, 72% of trials met enrollment goals on time, up from 59% in 2018.
17
Cell and gene therapy trials enroll median 22 participants, 85% retention.
18
Diversity-focused trials enroll 18% slower but retain 12% better.
Interpretation
Enrollment Rates Interpretation
While North America dominates global enrollment and innovative trial designs are showing real promise in boosting speed and diversity, the sobering reality is that many studies—especially in oncology and rare diseases—still struggle with slow recruitment, high dropout rates, and a persistent reliance on underperforming sites, creating a costly tug-of-war between scientific ambition and practical execution.
More related reading
04 · Category
Motivators and Incentives19 stats
01
Altruism motivates 78% of trial participants to enroll.
02
Financial reimbursement increases enrollment by 52% in Phase I healthy volunteer trials.
03
Access to novel therapies drives 65% of oncology patient participation.
04
Physician recommendation influences 89% of decisions to join trials.
05
Free medical care and monitoring attract 44% of uninsured participants.
06
Family support boosts participation likelihood by 37%.
07
Travel reimbursement offered in 68% of trials increases rural enrollment 29%.
08
Educational resources on trials raise willingness by 25%.
09
Success stories from prior participants motivate 51%.
10
Flexible scheduling (telehealth) incentivizes 43% more working participants.
11
Community outreach events lead to 22% higher enrollment rates.
12
Personalized risk-benefit counseling increases consent rates by 34%.
13
Lottery-style incentives (e.g., gift cards) boost retention 15%.
14
Hope for personal benefit cited by 72% of rare disease participants.
15
Peer support groups facilitate 28% of referrals to trials.
16
Tax deductions for trial expenses motivate 12% more middle-income.
17
Digital apps for tracking progress retain 19% more participants.
18
Matching donations to charities per visit incentivize 26%.
19
In diversity initiatives, cultural competency training raises trust 41%.
Interpretation
Motivators and Incentives Interpretation
While altruism may light the spark for many, the engine of clinical trial enrollment is pragmatically fueled by a complex blend of trust, access, support, and strategic incentives.
05 · Category
Participant Demographics20 stats
01
In the United States, women represent approximately 52% of clinical trial participants across all phases, but only 38% in Phase I trials due to safety concerns in early-stage testing.
02
Among US clinical trial participants aged 65 and older, 25% report participating in oncology trials, higher than the 18% national average for all ages.
03
Hispanic or Latino individuals constitute 7.5% of clinical trial enrollees in FDA-regulated trials from 2015-2020, despite being 18.9% of the US population.
04
In pediatric clinical trials (ages 0-17), only 12% of participants are from underrepresented racial minorities, compared to 41% in the general child population.
05
Rural residents make up 19% of US clinical trial participants, lower than their 20% share of the population, with 80% of trials located in urban areas.
06
Asian Americans account for 4.2% of participants in cardiovascular clinical trials, despite comprising 6% of the US population.
07
Patients with multiple comorbidities participate at a rate of 15% in chronic disease trials, influencing 22% higher dropout rates.
08
In 2021, 28% of US clinical trial participants had a college degree or higher, correlating with 35% higher enrollment in Phase III trials.
09
Low-income participants (below 200% federal poverty level) represent 22% of enrollees in community-based trials but only 11% in academic centers.
10
Veterans comprise 8% of clinical trial participants in mental health studies, with 45% aged 55+
11
In oncology trials, patients aged 18-39 years represent just 3% of participants, despite 12% incidence in that age group.
12
Native American/Alaska Native individuals are 0.4% of clinical trial participants, versus 1.3% population share.
13
Employed full-time individuals participate at 62% rate in trials allowing flexible scheduling, compared to 41% for unemployed.
14
In rare disease trials, 67% of participants are female, attributed to higher diagnosis rates in women for certain conditions.
15
LGBTQ+ individuals report 14% participation in HIV trials but only 5% in general population health trials.
16
In 2023, 31% of Phase II trial participants in Europe were over 70 years old, up from 24% in 2018.
17
African immigrants represent 2.1% of participants in infectious disease trials in the US.
18
Caregivers participate 18% more in trials offering childcare support, with 55% being female.
19
In neurology trials, participants with family history of disease enroll at 42% rate versus 28% without.
20
Obese participants (BMI >30) make up 39% of diabetes trial enrollees, matching prevalence.
Interpretation
Participant Demographics Interpretation
Clinical trial participation paints a portrait of an America where the path to medical advancement is paved with good intentions but littered with disparities, revealing that who gets a seat at the research table still depends too much on who you are, where you live, and what you can afford.
Reference
Cite This Report
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APA
Min-ji Park. (2026, February 13). Clinical Trial Participation Statistics. Gitnux. https://gitnux.org/clinical-trial-participation-statistics
MLA
Min-ji Park. "Clinical Trial Participation Statistics." Gitnux, 13 Feb 2026, https://gitnux.org/clinical-trial-participation-statistics.
Chicago
Min-ji Park. 2026. "Clinical Trial Participation Statistics." Gitnux. https://gitnux.org/clinical-trial-participation-statistics.
Sources & references
53 datasets cited across this report · attribution is report-level