title: Online Recruitment Methods for Web-Based and Mobile Health Studies: A Review of the Literature.
abstract: BACKGROUND
  Internet and mobile health (mHealth) apps hold promise for expanding the reach of evidence-based health interventions. Research in this area is rapidly expanding. However, these studies may experience problems with recruitment and retention. Web-based and mHealth studies are in need of a wide-reaching and low-cost method of recruitment that will also effectively retain participants for the duration of the study. Online recruitment may be a low-cost and wide-reaching tool in comparison to traditional recruitment methods, although empirical evidence is limited.
  
  
  OBJECTIVE
  This study aims to review the literature on online recruitment for, and retention in, mHealth studies.
  
  
  METHODS
  We conducted a review of the literature of studies examining online recruitment methods as a viable means of obtaining mHealth research participants. The data sources used were PubMed, CINAHL, EbscoHost, PyscINFO, and MEDLINE. Studies reporting at least one method of online recruitment were included. A narrative approach enabled the authors to discuss the variability in recruitment results, as well as in recruitment duration and study design.
  
  
  RESULTS
  From 550 initial publications, 12 studies were included in this review. The studies reported multiple uses and outcomes for online recruitment methods. Web-based recruitment was the only type of recruitment used in 67% (8/12) of the studies. Online recruitment was used for studies with a variety of health domains: smoking cessation (58%; 7/12) and mental health (17%; 2/12) being the most common. Recruitment duration lasted under a year in 67% (8/12) of the studies, with an average of 5 months spent on recruiting. In those studies that spent over a year (33%; 4/12), an average of 17 months was spent on recruiting. A little less than half (42%; 5/12) of the studies found Facebook ads or newsfeed posts to be an effective method of recruitment, a quarter (25%; 3/12) of the studies found Google ads to be the most effective way to reach participants, and one study showed better outcomes with traditional (eg in-person) methods of recruitment. Only one study recorded retention rates in their results, and half (50%; 6/12) of the studies recorded survey completion rates.
  
  
  CONCLUSIONS
  Although online methods of recruitment may be promising in experimental research, more empirical evidence is needed to make specific recommendations. Several barriers to using online recruitment were identified, including participant retention. These unique challenges of virtual interventions can affect the generalizability and validity of findings from Web-based and mHealth studies. There is a need for additional research to evaluate the effectiveness of online recruitment methods and participant retention in experimental mHealth studies.
authors.affiliation: University of Arizona, Department of Family and Community Medicine, Tucson, AZ, United States. taylorlane@email.arizona.edu.
authors.forename: Taylor S
authors.identifier: http://orcid.org/0000-0001-9387-5700
authors.initials: TS
authors.lastname: Lane
authors.forename: Julie
authors.identifier: http://orcid.org/0000-0001-8787-9190
authors.initials: J
authors.lastname: Armin
authors.forename: Judith S
authors.identifier: http://orcid.org/0000-0002-5911-4219
authors.initials: JS
authors.lastname: Gordon
mesh_terms: D006801:Humans; D063731:Mobile Applications; D018579:Patient Selection; D061108:Social Media; D011795:Surveys and Questionnaires; D017216:Telemedicine / Q000191:economics / Q000379:methods*
keywords: Internet health; apps; mHealth; online recruitment; review; social media