Association between Recruitment Methods and Attrition in Internet-Based Studies

Abstract

Internet-based systems for epidemiological studies have advantages over traditional approaches as they can potentially recruit and monitor a wider range of individuals in a relatively inexpensive fashion. We studied the association between communication strategies used for recruitment (offline, online, face-to-face) and follow-up participation in nine Internet-based cohorts: the Influenzanet network of platforms for influenza surveillance which includes seven cohorts in seven different European countries, the Italian birth cohort Ninfea and the New Zealand birth cohort ELF. Follow-up participation varied from 43% to 89% depending on the cohort. Although there were heterogeneities among studies, participants who became aware of the study through an online communication campaign compared with those through traditional offline media seemed to have a lower follow-up participation in 8 out of 9 cohorts. There were no clear differences in participation between participants enrolled face-to-face and those enrolled through other offline strategies. An Internet-based campaign for Internet-based epidemiological studies seems to be less effective than an offline one in enrolling volunteers who keep participating in follow-up questionnaires. This suggests that even for Internet-based epidemiological studies an offline enrollment campaign would be helpful in order to achieve a higher participation proportion and limit the cohort attrition.

Using Facebook ads with traditional paper mailings to recruit adolescent girls for a clinical trial

“…By comparison, our retention rates of 98% at posttest and 97% at 1-year follow up are high. These rates contrast with prior research that associated online recruitment with lower rates of retention compared to offline or face-to-face recruitment (Bajardi et al, 2014; Temple & Brown, 2012). …”

“…Indeed, Bajardi et al (2014), found that participants recruited online had lower follow-up rates than participants recruited through traditional methods. Perhaps the impersonal context of online recruitment that favors cost and time constraints also hinders rapport and relationship building (Temple & Brown, 2012).…”

Prenatal exposure to antibiotics and wheezing in infancy: a birth cohort study

“…Members of the cohort are children of mothers who have access to the internet and enough knowledge of Italian to complete online questionnaires. Recruitment is conducted actively through obstetrics clinics, and passively via the internet and the media [24]. ∼75% of participants are recruited actively, 20% passively and 5% comprise both modes.…”

Ten-year performance of Influenzanet: ILI time series, risks, vaccine effects, and care-seeking behaviour

“…An important cornerstone for success is the feedback of information to keep the participants involved and motivated. Although the specific recruitment strategies vary between countries (Bajardi et al, 2014), they tend to be based on mass communication. The websites contain a wealth of information on influenza, ILI and common cold, while the educational and scientific aims of the project are explained in direct mailings to schools, in repeated interviews on television and radio, and in newspapers.…”