The sample collected in the present study generally aligns with the existing literature detailing the demographic profiles of COVID-19 long-haulers [21]. Emerging demographic profiles demonstrate that long-haulers, as identified by their symptoms rather than diagnosis, tend to be older (i.e., 53.7, SD = 21.0), female (59.7%), White (61.3%), Black (14.7%), and Hispanic or Latino (17.7%) [21]. Additional literature demonstrates mixed findings on the long-COVID burden experienced by certain racial or ethnic groups [22]. The Long COVID Household Pulse Survey from the CDC’s National Center for Health Statistics, based on estimates between October 18 and 30th 2023, found that of adults who ever had COVID, Hispanic or Latino (29.1%) adults, non-Hispanic White (24.9%) adults, and non-Hispanic Black (26.1%) adults represented those most affected [22]. Emerging literature, utilizing national level data (i.e., BRFSS, NHIS), has found similar trends of long-COVID burdens among older adults, females, Hispanic or Latino adults, and adults with less than a college degree [23]. In alignment with the emerging demographic profile of COVID-19 long haulers this study presents promising results to recruit samples of long-haulers among those most burdened (e.g., race, ethnicity, education) but require additional considerations to recruit a sample representative of long-haulers by age. Further approaches prioritizing a fully representative sample may rely on a quota-based sampling strategy to control for the over- or underrepresentation within certain stratifications.
The low-cost recruitment efforts detailed in the present study resulted in a total sample of 460 participants from advertisements posted in 17 COVID-centric, public Facebook groups. These group-based, online recruitment methods possess strengths and limitations that must be considered relative to the resources available, target population, as well as privacy and confidentiality responsibilities. Typical online recruitment relies on the advertising features of platforms but can become costly when paying per day, by reach, or by click. Traditional recruitment via paid platform advertisements may, themselves, be associated with concerns of reach and representativeness in addition to limitations of high cost without assurance of data completeness or quality. Broad advantages and disadvantages of social media based recruitment methods include their access to broad audiences, targeted recruitment, rapid recruitment, user engagement, and reduced costs in contrast to challenges to representativeness, privacy concerns and control, as well as limited access [24]. These advantages and challenges must therefore be weighed, as related to recruitment method, in study design.
Recruitment utilizing Facebook’s group features differentiates itself from the costly methods of recruitment through paid advertisements. Findings reporting the efficacy of paid advertising recruitment approaches praise abilities to reach specific demographic groups to align with target populations but result in a variable average cost per participant ranging from USD $1.88 to USD $4.21 [25]. A systematic review of Facebook recruitment for health research reports a median cost per participant of $14.41 [11]. Although the algorithmic distribution of advertisements may be useful to researchers aiming to recruit a particular demographic, the need for caution due to its nonrandom targeting has been called for in the literature [26]. Samples recruited through paid Facebook advertisements have been found to be partially representative, overrepresenting young white women, with issues of selection bias, based on language used in the advertisement, impacting engagement [11], [27]. The present findings demonstrate strength not only in the ability to target recruitment and tailor campaigns, beyond basic demographics, based upon group topics and membership identity (i.e., disease condition), but also in that its cost (i.e., $2.17 per participant) is similar to that of the lower end of costs associated with Facebook advertisement-based recruitment. Further, as the raffle-based incentive was determined by the study team with consideration of available resources and appropriate compensation, there is the potential for future studies to operationalize a similar approach while following an alternate incentive structure.
Generally, recruitment through Facebook groups, rather than advertisements, leverages certain principles of community engaged research where group administrators act as community leaders, gatekeepers, and stakeholders. Social media platforms present a unique setting through which to sample hard-to-reach populations. Use of social media methods for recruitment has been advantageously described as providing a sampling frame for populations where probability sampling has otherwise been inconceivable or infeasible [25]. In reimagining the role of Facebook groups for recruitment, various outcomes have been reported. One disease-specific RCT conducted during the COVID-19 pandemic found group recruitment to be effective as 478 individuals expressed interest in participating, of which 404 were eligible to participate and contacted, to which 135 responded and the first 100 to respond were utilized as the sample [28]. Mixed findings exist where although one study posted in 123 groups and obtained a sample size of 87 participants, another posted in 42 groups and obtained a sample size of 4,000 [29], [30]. In considering differences in the proportion of groups posted in and the resulting sample size, a possible explanation considers that recruitment may be contingent upon the size of the target population aimed to be sampled, relevant demographics, and intensity or required commitment of participants to complete study activities [29].
The findings of the present study demonstrate the recruitment of a diverse and sufficient sample and provide support for Facebook group recruitment methods that have been emergingly utilized within the literature. In considering Facebook recruitment methods, the researcher should consider, in relation to their research question, the target population (e.g., size, accessibility, presence on Facebook, number of public groups), available resources (e.g., recruitment costs, participant incentive costs), timeline (e.g., administrator contact schedule, posting schedule, time between posts), potential for bias (e.g., measuring social support amongst members in online groups), study design (e.g., RCT challenges vs. cross-sectional challenges), and data collection or intervention methods (e.g., confidentiality and privacy safeguards between participants, use of additional data collection methods to reduce the potential for anticipated bias) [24]. An additional consideration for researchers aiming to employ similar methods is the impact of the posting profile on user trust, where a newly created study profile may be perceived differently than posts made from a researcher’s personal profile, but raises questions related to privacy and professionalism necessary to ensure an appropriate distance between researchers and participants is maintained while also building trust [29].
The present study presents strengths of survey recruitment through Facebook groups as a low-cost recruitment strategy that is easily targeted to a specific population and allows users to complete the study survey activities off-site on a HIPPA compliant survey platform. Facebook group-based recruitment has demonstrated promise when recruiting for both qualitative and quantitative work. A potential limitation of this recruitment method is related to the impact on sampling and should be weighed against population access, sampling frames, and sampling strategies. An additional limitation of this method is the ever-changing nature of platform functions and user demographics where the functionality of groups is likely to change over time as those who are active on the site or utilize certain functions may also change over time. Recommendations for future use of this method are to consider including groups with membership less than 1,000 and including private groups after administrator approval. Anecdotally, it is recommended that posts be made when users are more likely to be active (e.g., outside of typical working hours, on weekends), to increase visibility, and to consider that the life of a post has been here found to be a week but may differ based on the level of activity and engagement in each group. If the group administrators are receptive to posts for health-related research recruitment they could be asked to pin posts to the top of the group page, also increasing visibility.
In summary, the present methods detailed to recruit study participants from Facebook groups provide supportive evidence for this low-cost recruitment method to target disease- or condition-specific groups that may be otherwise hard-to-reach. Future research should further investigate differences in representativeness and bias present in studies recruiting through Facebook groups versus advertisements as well as the influence of differences in perception of recruitment materials on the sample recruited (e.g., length of post, language used, perception of post maker). There also exists the potential to interview Facebook group creators and administrators regarding their perceptions of group purpose, group regulation, as well as member and post approval decision-making, especially as related to health-related research posts. There is a clear and present need for a review and meta-analysis of recruitment efficacy across and between various disease specific groups to inform future recruitment and intervention tailoring efforts to better understand the context and concerns of a variety of populations (e.g., stigma, belonging, diagnosis, chronic vs. temporary).