title: 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.
authors.affiliation: GECO- Computational Epidemiology Group, Department of Veterinary Sciences, University of Torino, Torino, Italy; ISI Foundation, Turin, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Bajardi
authors.affiliation: ISI Foundation, Turin, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Paolotti
authors.affiliation: ISI Foundation, Turin, Italy; Laboratory for the Modeling of Biological and Socio-technical Systems Northeastern University, Boston, Massachusetts, United States of America; Institute for Quantitative Social Sciences at Harvard University, Cambridge, Massachusetts, United States of America.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Vespignani
authors.affiliation: London School of Hygiene and Tropical Medicine, London, United Kingdom.
authors.forename: Ken
authors.initials: K
authors.lastname: Eames
authors.affiliation: London School of Hygiene and Tropical Medicine, London, United Kingdom.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Funk
authors.affiliation: London School of Hygiene and Tropical Medicine, London, United Kingdom.
authors.forename: W John
authors.initials: WJ
authors.lastname: Edmunds
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, UMR-S 707, Paris, France; Université Pierre et Marie Curie-Paris 6, UMR-S 707, Paris, France.
authors.forename: Clement
authors.initials: C
authors.lastname: Turbelin
authors.affiliation: Institut National de la Santé et de la Recherche Médicale, UMR-S 707, Paris, France; Université Pierre et Marie Curie-Paris 6, UMR-S 707, Paris, France.
authors.forename: Marion
authors.initials: M
authors.lastname: Debin
authors.affiliation: ISI Foundation, Turin, Italy; Institut National de la Santé et de la Recherche Médicale, UMR-S 707, Paris, France; Université Pierre et Marie Curie-Paris 6, UMR-S 707, Paris, France.
authors.forename: Vittoria
authors.initials: V
authors.lastname: Colizza
authors.affiliation: Aquisto-Inter BV, Amsterdam, The Netherlands.
authors.forename: Ronald
authors.initials: R
authors.lastname: Smallenburg
authors.affiliation: Aquisto-Inter BV, Amsterdam, The Netherlands.
authors.forename: Carl
authors.initials: C
authors.lastname: Koppeschaar
authors.affiliation: Instituto Gulbenkian de Cincia, Oeiras, Portugal.
authors.forename: Ana O
authors.initials: AO
authors.lastname: Franco
authors.affiliation: Instituto Gulbenkian de Cincia, Oeiras, Portugal.
authors.forename: Vitor
authors.initials: V
authors.lastname: Faustino
authors.affiliation: Public Health Agency of Sweden, Stockholm, Sweden.
authors.forename: AnnaSara
authors.initials: A
authors.lastname: Carnahan
authors.affiliation: Public Health Agency of Sweden, Stockholm, Sweden.
authors.forename: Moa
authors.initials: M
authors.lastname: Rehn
authors.affiliation: Department of Medical Sciences, University of Turin and CPO-Piemonte, Turin, Italy.
authors.forename: Franco
authors.initials: F
authors.lastname: Merletti
authors.affiliation: Centre for Public Health Research, Massey University, Wellington, New Zealand.
authors.forename: Jeroen
authors.initials: J
authors.lastname: Douwes
authors.affiliation: Centre for Public Health Research, Massey University, Wellington, New Zealand.
authors.forename: Ridvan
authors.initials: R
authors.lastname: Firestone
authors.affiliation: Department of Medical Sciences, University of Turin and CPO-Piemonte, Turin, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Richiardi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015331:Cohort Studies; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D007251:Influenza, Human / Q000453:epidemiology*; D020407:Internet; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D010358:Patient Participation; D018579:Patient Selection; D011159:Population Surveillance; D015995:Prevalence; D011795:Surveys and Questionnaires; D055815:Young Adult