Enrollment in Clinical Trials: Statistics and Patient Recruitment Strategies

Clinical trials are a vital stage of the process of finding and testing new ways to detect, prevent, and treat human disease. Recruiting patients to participate in these trials, however, has often been and continues to be one of the most challenging aspects of getting a trial up and running.

Drug developers, pharmaceutical companies, and other organizations who sponsor clinical trials are continually looking to refine their patient recruitment strategies to make enrollment in clinical trials more appealing to participants and more effective and efficient overall.

By understanding the patterns of enrollment and recruitment in clinical trials and the common challenges encountered, researchers and sponsors can be better equipped to recruit patients effectively through well-designed clinical trial recruitment strategies.

Clinical trial recruitment statistics and background information

Clinical trial enrollment statistics are somewhat disheartening. According to a 2020 study by HINTS, 41% of US adults admitted not being aware of clinical trials at all. Only 8.9% of respondents in that study reported having been invited to participate in a clinical trial, of which less than half eventually enrolled.

As many as 86% of clinical trials are delayed and don’t meet original recruitment deadlines, and a high percentage of trials do not meet accrual targets at all. These delays cost sponsors between $600,000 and $8 million USD per day of delay. Screen failures (prospects who are screened but don’t end up enrolling) cost sponsors an average of $1,200 per failed enrollment. Before we get into the reasons that may explain these statistics, let’s try to understand what motivates people to enroll in clinical trials in the first place.

Why do people enroll in clinical trials?

There are multiple reasons why individuals may wish to take part in clinical trials, such as:

  • Access to novel therapies: Clinical trials offer patients the opportunity to try a new therapy or medication that is not yet available to the general public and might not be available anytime soon. Especially for patients who are not responding to currently available treatments, this may be an especially strong motivator.
  • Finding a new treatment or cure: The hope of finding an effective treatment or cure for a given disorder or disease, which could in turn help many other people around the world with the condition, is also a common motivation for taking part in a clinical trial.
  • Finding answers: Humans are naturally curious to find answers to questions and know more about their own situations. The idea that clinical trials may help them understand their condition better is another reason for enrollment in clinical trials.
  • Affordable or free treatment: In most clinical trials, the medication or treatment is provided for free, or at least at a relatively lower cost, along with additional attention from the medical staff.
  • Taking control of their health: Participating in a clinical trial also helps the participants engage more actively with their condition and their own medical care. They may learn more about their disorder or disease, factors that contribute to or aggravate it, and potential ways to feel better. Actively participating in their healthcare decisions is also empowering and may help patients feel more in control of their health.

How many people participate in clinical trials each year?

The participation rates in clinical trials vary year by year. For instance, 105,808 individuals took part in clinical trials worldwide in 2015, but this number significantly dropped to just 25,941 in 2016. The typical number of participants in a single clinical trial ranges from 10 or 20 to hundreds or thousands, depending on the type, stage, and scope of the clinical trial.

According to an FDA report on diversification in clinical trials, 12% of the US population is African-American, but they represent only 5% of clinical trial participants. 16% of the US population is Hispanic, but they represent only 1% of clinical trial participants. Diversity in clinical trial populations is important for the sample and study results to best encompass the different treatment responses amongst sub-populations (sexes, ethnicities, age groups, etc.) due to genetic variations. For this reason, there is increasing discussion around enrolling minorities and under-represented groups in clinical research. Platforms like Power are working towards increasing diversity in clinical research by equalizing access to clinical trial opportunities - inclusive research starts with solving patient accessibility.

How big is the clinical trial recruitment market?

The global clinical trial recruitment market was estimated at $3.6 billion in 2021, and is estimated to grow significantly to $5.45 billion by 2030. The major growth in the global clinical trial recruitment market is largely due to increases in research studies and advancements in the pharmaceutical and medical industries. However, there was a decline in the rate of clinical trial recruitment during the COVID-19 outbreak since many facilities were shut down and patient travel was restricted due to the lockdowns. Nonetheless, this trend also accelerated the adoption of hybrid or decentralized clinical trials (DCTs) with aspects conducted remotely.

Current challenges in clinical trial patient recruitment and enrollment

As hinted at through the statistics mentioned above, challenges in clinical trial patient recruitment and enrollment are largely related to lack of awareness of and access to information about clinical trials on the participant side, and difficulties reaching accrual targets, either on time or overall, for investigators/sponsors.

At first, the COVID-19 pandemic caused a slowdown in clinical trial enrollment, but soon thereafter accelerated an industry-wide shift toward new types of trials and new possibilities for patient recruitment and enrollment. In the following sections, we will break down the main challenges in patient recruitment and then propose solutions for improving patient recruitment in clinical trials under this newly evolving landscape.

Difficulties in clinical trial recruitment for sponsors and study sites

One of the major challenges sponsors face in clinical trial patient recruitment and enrollment is patient accessibility. Many sponsors find it difficult to recruit enough patients (and the right patients) because the catchment area is limited. Traditional recruitment focuses on enrolling participants who are already part of the study site’s network of patients, which dramatically limits the patient pool.

Recruiters have also started to leverage patient databases at specialty clinics treating the condition being studied, however, the prospective patients would have to have visited one of these clinics, which again significantly narrows down the pool of patients. Having access to a broader pool of potential participants, not restricted by such specific criteria, opens up the patient pool.

On the other hand, casting wide nets without any specificity at all is equally likely to lead to disappointing results. Filtering out large numbers of participants who express interest but turn out to be ineligible, for any number of reasons (i.e., not fitting all, or even one, of the often numerous eligibility criteria), is a labour-intensive process that yields limited results. Relatedly, limited budgets and resources allocated to the recruitment stage, either at individual sites or for the trial overall, can also limit the achievement of accrual targets. It has been suggested that proper planning and design of clinical trial recruitment strategies, including appropriate budgeting of time and monetary resources, may be the most promising method for improving recruitment efforts.

Patient barriers to enrollment in clinical trials

On the other side of the equation, there are also significant barriers to enrollment faced by patients, largely related to information, accessibility, and practical considerations. As mentioned, the clinical research industry has traditionally been characterized by unequal representation across different sub-populations, so significant efforts are being made to improve participation rates amongst diverse populations.

Lack of awareness and accessibility

Many people are unaware of clinical trials, making it one of the biggest barriers to patient enrollment. In a study from 2001, 85% of survey respondents were entirely unaware or unsure if participation was a possibility for them when they were diagnosed, but 75% admitted that they would have been willing to participate in a clinical trial had they been aware of the possibility.

It’s no surprise that such a large portion of the population isn’t aware of clinical trial opportunities, when we consider that only about 5% of physicians in the US participate in clinical trials. And access to the clinical trials has traditionally been limited to the sites where the clinical research is being conducted - typically these have been prestigious medical institutions. So, there are patients who are willing to participate in research yet are not aware of and do not have a way to easily access these opportunities.

Travel burden

For patients who are aware of the possibility of enrolling in clinical trials, other barriers may commonly prevent them from participating. One of the major difficulties is transportation to and from study sites for each study visit, which implies an investment of both time and money. This is also a major reason for dropouts, since many patients find this frequent travel burdensome, particularly if the trial requires frequent visits and/or if the patient lives far away from the trial site.

Financial considerations

The overall cost of participating in a clinical trial may turn out to be unmanageable for patients. Aside from the costs involved in traveling to and from the clinical trial site for the visits, the general time commitment required may imply unpaid time off work, childcare expenses, overnight stays away from home, and other things that result in financial burden.

How can enrollment in clinical trials be improved?

Now that we understand some of the main reasons for the poor clinical trial enrollment statistics, here we present some solutions for improving enrollment rates and reducing delays and associated monetary losses. This list provides general, overarching considerations to keep in mind for designing effective clinical trial patient recruitment strategies, and in the next section we will go through some solutions to consider.

  • Conduct a feasibility study for the clinical trial first. This ensures not only that the study is economically and practically feasible, but whether or not it will likely be possible to recruit the number of participants required to obtain sufficient statistical power in the results.
  • Use clear, transparent language in clinical trial information provided to patients to ensure patients are aware of the scope of the trial as well as the eligibility criteria. Provide relevant and actionable information.
  • Dedicate effort to thorough pre-planning and design of recruitment strategies. Outreach efforts should reach the right audiences and resonate with them.
  • Design patient-centric protocols. Increased consideration of patient experience means that the trial is more likely to be appealing as it implies lower patient burden and/or offers more potential benefit. Consider how the participant would feel going through all stages of the study, and try to make it easier or more comfortable for them.
  • Leverage digital tools and trends. Technological advances have opened up new doors for clinical trials, including in recruitment and patient enrollment and engagement. It is worth familiarizing yourself and your organization with the latest trends and possibilities.
  • Promote collaboration between stakeholders and sites to enhance teamwork and leverage the combined experience and capabilities of different teams. This may include third-party vendors offering helpful recruitment tools, or even external recruitment agencies specializing in clinical trial patient recruitment.
  • Share enrollment success stories. Success stories may boost the morale of the study team, encourage the sharing of experiences between sponsors to improve future enrollment efforts, and also entice participants to join a trial.

Patient recruitment strategies for clinical trials

Now let’s take a closer look at 3 specific solutions for improving clinical trial accrual rates.

Solution 1: Open up the catchment area and access new patient pools

As we covered briefly in the section on challenges in clinical trial recruitment, one of the biggest blockers in patient recruitment is patient accessibility. So the first solution is to open up the catchment area and access new patient pools. This involves going beyond clinic-led recruitment to capture a larger patient pool.

One way to do this is by leveraging a platform like Power. Power is the only self-serve patient recruitment marketplace where patients and researchers can connect seamlessly. With Power, patients can search for leading medical research for their specific conditions, in their specific geographies, and filter by their specific requirements. On the other side, researchers can create an account on Power, verify their trial info and start matching with patients looking for clinical trials (without any need for IT, training, or other technical set up). By equalizing access to clinical trial opportunities, Power both opens up the patient pool and sees a much more diverse patient population.

Solution 2: Adopt a patient-centric approach and aspects of decentralization

Patient centricity has become a hot topic in the healthcare and clinical research industry. The basic principle is that patients’ first-hand experiences become an overarching priority in clinical research. As sponsors and investigators make increased efforts to empathize with the patient’s experience throughout the entire clinical trial, they are able to design better recruitment campaigns that resonate with the target population, design protocols that are more attractive to potential participants, and improve patient engagement and retention overall. Patient-centric trials aim to ensure patients feel seen, appreciated, valued, and have a generally positive experience in the trial. Positive past experiences will make patients more likely to enroll in subsequent trials.

Further, new advancements in telehealth and technology have opened doors for fully-remote (decentralized) clinical trials, remote monitoring and study visits, and new avenues for outreach and recruitment. Online recruitment campaigns have become the new norm; wider groups of people can be reached more easily, and if a trial can be made fully-remote, geographical location would no longer represent a significant barrier to recruitment nor participation.

Importance of protocol design: Considerations for patient-centric trials

Patient centricity must be incorporated into the study protocol itself. When designing the study and formulating the protocol, ask questions such as the following to consider ways to ease patient burden and make the trial more enticing:

How many visits are needed during the trial?

  • Are all of these visits absolutely necessary?
  • Can any or all of them be conducted via remote methods?
  • Would readily available tools make it easy to make these visits fully remote?
  • Can wearable devices or telehealth allow health endpoints to be collected or monitored automatically or remotely?

How flexible can the scheduling of the visits be?

  • Are visits scheduled during normal working hours, requiring patients to take time off work (which may be unpaid/not possible)?
  • Could local sites be set up temporarily to decrease travel distance, or could healthcare providers visit patients at home?

What financial costs may be incurred for patients during their participation?

  • Is there room in the study budget to offset some of these costs, or to compensate patients for participation in general or on a distance-traveled basis?

Are all the data intended to be collected necessary for interpretation of the results?

  • Is the number of surveys, questionnaires, study visits, etc. manageable for patients, considering that they also have other commitments?
  • Could any of these be combined or obviated?

Will patients have open support channels to quickly address any concerns that may come up?

  • Will it be easy for them to contact their primary point-of-contact or study physician?
  • Can telehealth methods be used to set up and facilitate such communication?

Solution 3: Diversify your recruitment strategy

It is unlikely that a single-sided approach will help you achieve your recruitment targets efficiently. Beyond designing attractive, patient-centric protocols including decentralized components where possible, it will likely be necessary to tackle recruitment from various angles. There are many potential tools, technologies, and approaches that can be combined to create a robust and effective recruitment strategy. Consider the following aspects:

  • Pharmacy and physician referrals. Patients tend to trust their healthcare professional contacts most for information and referrals.
  • Consult with patient advocacy groups to understand your target population as well as potentially get in touch with eligible candidates.
  • Launch online recruitment campaigns utilizing social media platforms such as Facebook and or search engines such as Google to take advantage of their massive user bases.
  • Partner with vendors offering specialized or holistic solutions, which may be focused on recruitment or on management of the entire trial.


Patient enrollment in clinical trials is a top priority for clinical research facilities, sponsors, and sites, but it also represents a major challenge and bottleneck in clinical trials.

If you’re recruiting for a study, check out Power - it takes minutes to join our marketplace and start matching with patients.