Abstract
INTRODUCTION:
Offering remuneration for participation in studies of aging and Alzheimer Disease (AD) may improve recruitment, particularly among minoritized and low-income groups. But remuneration may also raise ethical problems and reduce altruistic motivations for participation.
METHODS:
A nationally representative sample of Americans (N=2,030) with large (N>500) Black and Hispanic oversamples was asked about willingness to participate in a longitudinal AD cohort study after random assignment of remuneration ($0, $50/visit, $100/visit). Respondents were then asked about their perceived burden, risks, and societal contribution from participation.
RESULTS:
An offer of remuneration increased willingness to participate, with no difference between $50 and $100. The increase was similar across racial, ethnic and income groups. Remuneration did not affect perceived risks or altruistic benefits. Compensation caused whites and Hispanics, but not Blacks, to lower perceived burden.
DISCUSSION:
Modest levels of remuneration are likely to improve recruitment to AD research studies without causing collateral ethical or motivations problems. Remuneration does not differentially enhance minority recruitment.
Keywords: Remuneration, Recruitment, Study Participation
1. Introduction
The recruitment and retention of diverse study participants is critical to the progress of Alzheimer Disease (AD) research.1, Such studies often recruit and follow healthy adults, which may be particularly important for understanding how to prevent AD. 2,3 Many studies have trouble attracting sufficient volunteers, particularly participants from minority populations, which leads to unrepresentative studies and potentially non-generalizable results.1,4,5,6
One potential strategy for improved recruitment and retention is remuneration for participation. Such compensation may serve as a financial inducement.7 But it also could play an important role in reducing the perceived burden of participation.8 Study participation can involve considerable demands on participants’ time, logistical inconveniences, and diagnostic testing that may prove mentally and emotionally exhausting. The resulting perceived burden has deleterious effects on recruitment and on study participation in terms of missed study visits and risk of dropout.9,10 Consequently, remuneration could be valuable for recruitment and retention of study participants if it lowers participants’ expectations and perceptions about study burden.11,12,13
In theory, remuneration may be particularly important for increasing the recruitment of minoritized participants and those with low socio-economic status. This is both because it is a financial inducement and because it helps offset the often higher burden of participation experienced by these groups.10,13,14,15,16 For example, minoritized groups may encounter language barriers or face longer travel times.13,17 Thus, remuneration may be especially influential in recruiting participants from under-represented groups.18
However, remuneration also raises potentially important ethical concerns. In particular, compensation may undermine informed consent by causing potential participants to reduce their perceived risks of participation.15,19 Also, there is a concern that compensation can “crowd out” a participant’s altruistic motivations, as extrinsic motivations associated with compensation may cause participants to discount their intrinsic motivations (e.g., altruism or civic duty) for participation.20
While remuneration is a commonly used incentive in medical research, evidence that it enhances recruitment of healthy study participants is limited. Research that surveys existing study subjects about their motivations or asks potential subjects about their interest in participating often identifies compensation as a facilitator.7 However, the small number of studies where remuneration is experimentally manipulated show mixed effects on participation in or willingness to participate in research studies.21,22,23,24,25,26,27 Only one experimental study has examined any of the consequences of remuneration for perceived burden, altruistic motivation, and risk perceptions, showing remuneration did not adversely affect risk perceptions.21 Research on recruitment of participants in AD studies also identifies compensation as a potential facilitator, but no study has estimated the effect of compensation on participation or willingness to participate or examined whether it influences burden, risk perceptions, or altruistic motivations.28,29 In this study, we aimed to estimate the potential impact of different levels of compensation on study participation, perceived burden, risk perception and altruistic motivations through a randomized survey experiment conducted with healthy adults. We also examined potential differential effects of remuneration across racial and ethnic groups. Specifically, the large over-samples of Blacks and Hispanics provide an unusual opportunity to obtain precise estimates of their responses to remuneration and compare them with the responses of white respondents.
2. Methods
2.1. Participants
The primary analyses in this study included 2,030 respondents (US residents at least 18 years old) enrolled in the AmeriSpeak panel survey conducted in November-December 2021 by the National Opinion Research Center (NORC) for the Weidenbaum Center at Washington University in St. Louis. The survey uses probability weights that ensure a nationally representative sample of the U.S. adult population. The survey was reviewed and deemed exempt by the Washington University Institutional Review Board. Based on respondent self-identification, the sample included 922 non-Hispanic whites, 505 non-Hispanic Blacks, 501 Hispanics, 38 non-Hispanic Asians, and 64 non-Hispanic respondents of other or mixed race. We excluded from the analysis the twelve respondents who reported having been diagnosed with Alzheimer Disease.
2.2. Survey Instrument
All respondents were presented with a description of participation in a hypothetical study comparable to longitudinal ADRC studies. The vignette was very similar to one asked in past studies of willingness to participate in AD cohort studies. 31,32 It included common study features such as annual visits involving tests of memory, blood samples, and a physical examination and the need for a study partner. (For details about the survey instrument, see “Survey Design and Survey Questions” in the supplemental materials.)
After presenting the hypothetical study, the vignette included a sentence describing remuneration of either $50/visit, $100/visit, or no remuneration. Through random assignment, one-third of respondents were presented with a vignette for each of these amounts of remuneration (see Figure 1). These are plausible compensation amounts, given current practice in longitudinal cohort studies. One of our co-authors (AD) queried the Outreach, Recruitment, and Engagement Cores of 16 ADRCs about their remuneration practices for longitudinal studies of healthy adults. Of those offering compensation, the median amount was $50/visit, with a range of $20/visit to $80/visit.
Figure 1:
Randomization Flowchart
Immediately following the presentation of the vignette, we asked respondents about their willingness to participate in the hypothetical study. We then asked four questions that capture important concerns about the consequences of remuneration. The order of presentation of these four questions was randomized. We asked one question about the perceived demand on a participants’ time, which is a commonly registered source of burden identified by study participants in such studies.7,30 We asked two questions about perceptions of common sources of risk from participation: that information about their health would be improperly used and that they would learn bad news about their health. Finally, we asked about whether they perceived their participation as beneficial to society. All questions were presented on a 5-point Likert scale: strongly agree, agree, neither agree nor disagree, disagree, strongly disagree. The responses were coded so that the variable ranges from 0 (strongly disagree) to 4 (strongly agree).
The survey also included information about the respondents’ sex, income, area of residence, race, and ethnicity. Respondents were asked to classify their combined household income into one of four categories: less than $30,000, $30,000-$60,000, $60,000-$100,000, or $100,000 or more. We created a dummy variable “low income,” coded 1 for the lowest quartile and coded 0 otherwise. Respondents were also asked to choose one or more categories from a list to indicate their race and ethnicity. We created dummy variables based on their responses. Respondents were classified as “white” if they self-identified as non-Hispanic white, “Black” if they self-identified as Black or African American, non-Hispanic, “Asian” if they self-identified as Asian American, non-Hispanic, and “Hispanic” if they self-identified as Hispanic or Latino. A small number of respondents (N=64) did not self-identify in any of the aforementioned groups and were coded as “Other.” Summary statistics are presented in Table 1.
Table 1:
Demographic Summary Statistics*
| $0 Remuneration | $50 Remuneration | $100 Remuneration | |
|---|---|---|---|
|
| |||
| Female % | 54.2 | 52.0 | 53.8 |
| Age (years) | 48.4 | 48.8 | 48.1 |
| White % | 45.7 | 46.3 | 45.0 |
| Black % | 23.5 | 24.4 | 26.5 |
| Hispanic % | 25.6 | 24.9 | 22.9 |
| Asian % | 1.8 | 1.4 | 2.5 |
| Other race % | 3.3 | 3.0 | 3.0 |
| Low income % | 30.6 | 26.9 | 27.4 |
| Metropolitan Resident % | 87.3 | 86.3 | 86.7 |
| Education Level (1–5) | 3.2 | 3.2 | 3.2 |
Note: Statistics are based on the unweighted survey data.
Missing data were rare: all survey questions analyzed received responses from at least 98.8% of respondents surveyed. Respondents who did not answer a survey question were eliminated from the related analysis. See the supplemental materials for detailed descriptions of missing data for each survey question.
2.3. Statistical Methods and Analysis
The data analysis proceeded in three stages using STATA 15.0 statistical software. We computed descriptive statistics to characterize respondents’ willingness to participate and their perceptions about the burden, risks, and social benefit of participation. Group differences were evaluated with difference in proportion tests. Second, we estimated the effect of different levels of remuneration on willingness to participate with ordered logistic regression analyses. We evaluated differences in the effect of the three levels of compensation with Wald tests. Finally, we used ordered logistic regressions to estimate the effect of an offer of remuneration on respondents’ perceptions of the burden, risks, and societal benefit of participation. Differences in the effect of remuneration across subgroups were estimated with interaction terms in the regression models.33 In these models, the marginal effects of remuneration ($50, $100, and $50 or $100) relative to no remuneration were calculated with the “margins” procedure. We focus on the marginal effects of remuneration on the probability a respondent chooses “agree” on the 5-category Likert scale for the relevant dependent variables (e.g., willingness to participate).
3. Results
Respondents varied considerably in their willingness to participate in the hypothetical AD study (Table 2). Almost half of respondents (32% agree and 17% strongly agree) agreed that they would participate in the hypothetical study. A minority disagreed they were willing to participate (8% strongly disagreed and 15% disagreed) and 28% neither agreed nor disagreed. The difference in the share of white respondents (51%) and Black respondents (40%) in agreement that they would participate was statistically significant (p<0.01). Hispanics had a lower average level (46%) of agreement than did whites, but the difference was not statistically significant (p>0.07). The modal respondent (a) neither agreed nor disagreed that participation would take too much time or that it would result in learning bad news about their health, (b) agreed that participation would benefit society, and (c) disagreed that they feared information from their participation could be used against them.
Table 2.
Perceptions of Study Participation (median, mode)
| Willingness to Participate in AD Research Study | Anticipated Burden from Study Participation | Anticipated Risk of Disclosure of Results | Anticipated Risk of Learning Bad News | Anticipated Societal Contribution | |
|---|---|---|---|---|---|
|
| |||||
| Full sample | 2, 3 | 2, 2 | 1, 1 | 2, 2 | 3, 3 |
| $0 offer | 2, 3 | 2, 2 | 2, 1 | 1, 1 | 3, 3 |
| $50 offer | 3, 3 | 2, 2 | 1, 1 | 1, 1 | 3, 3 |
| $100 offer | 3, 3 | 2, 2 | 1, 1 | 2, 2 | 3, 3 |
| white | 3, 3 | 2, 2 | 1, 1 | 1, 1 | 3, 3 |
| $0 offer | 2, 3 | 2, 2 | 1, 1 | 1, 1 | 3, 3 |
| $50 offer | 3, 3 | 2, 1 | 1, 1 | 1, 1, | 3, 3 |
| $100 offer | 3, 3 | 2, 1 | 1, 1 | 2, 2 | 3, 3 |
| Black | 2, 2 | 2, 2 | 2, 2 | 2, 2 | 3, 3 |
| $0 offer | 2, 2 | 2, 2 | 2, 2 | 2, 2 | 2, 2 |
| $50 offer | 2, 2 | 2, 2 | 2, 2 | 2, 2 | 3, 3 |
| $100 offer | 2, 2 | 2, 2 | 2, 2 | 1, 1 | 3, 3 |
| Hispanic | 2, 2 | 2, 2 | 2, 2 | 2, 2 | 3, 3 |
| $0 offer | 2, 2 | 2, 2 | 2, 2 | 2, 2 | 3, 3 |
| $50 offer | 2, 2 | 2, 2 | 2, 2 | 2, 2 | 3, 3 |
| $100 offer | 2, 2 | 2, 2 | 2, 2 | 2, 2 | 3, 2 |
| Low Income | 2, 2 | 2, 2 | 2, 2 | 2, 2 | 3, 3 |
| $0 offer | 2, 2 | 2, 2 | 2, 2 | 2, 2 | 3, 3 |
| $50 offer | 2, 2 | 2, 2 | 2, 2 | 2, 2 | 3, 3 |
| $100 offer | 3, 2 | 2, 2 | 2, 2 | 2, 2 | 3, 3 |
Note: All variables are measured on 5-point Likert agreement scale ranging from 0 (strongly disagree) to 4 (strongly agree). These statistics are based on probability weights to ensure representativeness of the sample.
It is important to note that the survey included 500 Black and 500 Hispanic respondents, which provide much greater statistical power for estimates for those subgroups than is typically available in nationally representative surveys. In contrast, we have a very small sample of Asian Americans (38 respondents). Consequently, the analysis focuses particularly on Black and Hispanic participants and comparisons of those groups with whites.
Respondents offered remuneration were more willing to participate than respondents who were not (Figure 2; Tables SM1 and SM2 in supplemental materials). However, the level of compensation did not affect participation. The difference in the effect of offering $50/visit compensation and $100/visit compensation was not statistically significant for white (p>.43), Black (p>.87), Hispanic (p>.20), or low income (p>.33) respondents.
Figure 2. Effect of Remuneration Offer on Willingness to Participate Relative to No Offer.
The figure is based on the ordered logistic regression results presented in Tables SM1 and SM2 in the supplemental materials. The marginal effects indicate the change in the probability of choosing “agree” on the Likert scale in response to the statement “I would be willing to join such a study about Alzheimer disease” that is associated with a change from an offer of $0 compensation to the designated amount of remuneration.
The size of the effect of any offer of remuneration ($50 or $100/visit) was similar across these subgroups, indicating respondents from minoritized and low-income groups were not more responsive to compensation than respondents in general (Figure 2; Table SM1 in supplemental material). For white respondents, an offer of compensation of $50 or $100 was associated with a 0.06 increase in probability of stating they “agree” they are willingness to participate relative to an offer of no monetary compensation. The difference between this marginal effect and the marginal effect for Black (p>.76) and Hispanic (p>.75) respondents was not statistically significant. Similarly, the effect of any remuneration for low-income respondents was not different (p>.54) from that for higher income respondents.
The size of the effect of an offer of any remuneration is modest, but substantively important relative to a prominent predictor of participation: trust in medical researchers. 29, 34, 35 For reference, Model 9 in Table SM1 (supplemental materials) estimates the effect of respondents’ trust in medical researchers on their willingness to participate. The general effect of any remuneration on willingness to participate (a 0.062 increase in the probability of choosing “agree” to participate) is almost as large as the effect of a respondent changing from disagreeing to agreeing that medical researchers are trustworthy (a 0.076 increase).
On average, an offer of remuneration reduced respondents’ probability of agreeing that participation would be burdensome by 0.08 (Figure 3; Tables SM3 and SM4 in supplemental materials). However, this effect did hold for Black respondents; remuneration does not have a statistically significant effect on their anticipated burden from participation.
Figure 3. The Effect of Any Remuneration Offer on Study Perceptions Relative to No Offer.
The figure is based on the ordered logistic regression results presented in Tables SM3 and SM4 in the supplemental materials. The marginal effects indicate the change in the probability of choosing “agree” on the Likert scale in response to the statements about potential consequences of participating in the study that is associated with a change from an offer of $0 compensation to an offer of $50 or $100. For exact wording of the statements about the consequences of participation, see the supplemental appendix.
Remuneration did not have a statistically significant effect on respondents’ perceived contribution to society from their participation (Figure 3). Finally, an offer of remuneration had no statistically significant effect on respondents’ perceived risks from participation (Figure 3). This was true for both the anticipated risk of learning bad news about one’s health and the anticipated risk of the participant’s information from the study being used against the participant. The estimated effects for these two risks were statistically insignificant for all racial/ethnic groups.
4. Discussion
Overall, survey respondents indicated a similar willingness to participate to that of related studies. Almost half (49%) of survey respondents were willing to participate in a longitudinal AD study. This is broadly consistent with the past studies of willingness to participate in hypothetical longitudinal studies and exactly the same share of respondents willing to participate in a very similar hypothetical longitudinal study of AD in a 2014 survey.31,36,37
Remuneration is a potentially valuable tool for recruitment of study subjects to longitudinal research studies of AD. It has a beneficial effect on recruitment from minoritized and low-income groups, although that effect is no larger than it is for whites. Thus, remuneration can be a tool for increasing the number of study participants from under-represented groups.
Interestingly, increasing the amount from $50 to $100 did not cause respondents to express greater willingness to participate. Nevertheless, for either amount of compensation, the effect on participation is substantively important; the marginal effect of remuneration on participation is almost as impactful on willingness to participate as a common facilitating factor for participation: trust in medical researchers.
The impact of remuneration on participation was generally benign in its effects on how respondents viewed participation. We found that remuneration caused respondents to reduce their anticipated burden from participation in general and in all subgroups except Blacks. This exception is notable, since a common argument for offering remuneration to Blacks is to offset the perceived burden of participation. 10,13,14,16,18
Remuneration does not appear to raise ethical concerns related to perceived risks of participation or concerns about “crowding out” altruistic motivations. Respondents offered remuneration perceived the risks of participation and anticipated contribution to society through participation at similar levels to those not offered remuneration. This was true in general and among all relevant subgroups: non-Hispanic whites, Asians Americans, Blacks, Hispanics, and low income.
That remuneration has similar effects on recruitment across racial, ethnic, and income groups indicates that remuneration does not raise ethical concerns about undue burden. To the extent specific groups are more responsive to financial inducements, then the burden of research studies offering compensation may fall disproportionately on those groups. Our results show that compensation improves willingness to participate for these groups but that it does not do so disproportionately.
Finally, to the extent other areas of medical research require participants to adhere to similarly demanding longitudinal protocols, these results are of broader value to improving recruitment of healthy study participants. Notably, the results indicate that relatively modest compensation is as effective as more generous payments.
Among the limitations of this study is that it relies on survey evidence about self-reported willingness to participate in a hypothetical study, which may not accurately capture respondents’ willingness to participate in an actual AD cohort study. However, past studies show that variation in responses to such survey questions correlate positively with actual behavior.38,39 Also, we only considered a limited set of compensation amounts. We cannot, for example, conclude that $50/visit is the lowest amount necessary to induce participation; perhaps smaller amounts would have similar effects to those shown here for $50 and $100/visit. We also cannot determine whether the offer of remuneration is effective because of the monetary compensation or simply as a gesture of gratitude or recognition for the participant’s time. Relatedly, the analysis did not engage another potential reason for remuneration: as a sign of respect for the participant’s contribution. Our survey did not include questions about whether respondents’ felt that their potential study participation would be treated with respect. Finally, the study findings may not generalize to recruitment of study participants who have been diagnosed with AD or preclinical AD.
Supplementary Material
Acknowledgments:
The Weidenbaum Center on the Economy, Government, and Public Policy at Washington University in St. Louis funded and managed the survey. Dr. Chengjie Xiong, PhD provided advice about statistical estimation.
Funding/Support:
Jorge Llibre-Guerra is supported by NIH-NIA (K01AG073526), the Alzheimer’s Association (AARFD-21-851415, SG-20-690363), the Michael J. Fox Foundation (MJFF-020770), the Foundation for Barnes-Jewish Hospital and the McDonnell Academy.
John C. Morris is funded by NIH grants # P30 AG066444; P01AG003991; P01AG026276; U19 AG032438; and U19 AG024904.
Footnotes
Conflict of Interest Disclosures:
None of the authors or their families owns stock or has equity interest (outside of mutual funds or other externally directed accounts) in any pharmaceutical or biotechnology company.
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