title: Benefits of extensive recruitment effort persist during follow-ups and are consistent across age group and survey method. The TRAILS study.
abstract: BACKGROUND
  Extensive recruitment effort at baseline increases representativeness of study populations by decreasing non-response and associated bias. First, it is not known to what extent increased attrition occurs during subsequent measurement waves among subjects who were hard-to-recruit at baseline and what characteristics the hard-to-recruit dropouts have compared to the hard-to-recruit retainers. Second, it is unknown whether characteristics of hard-to-recruit responders in a prospective population based cohort study are similar across age group and survey method.
  
  
  METHODS
  First, we compared first wave (T1) easy-to-recruit with hard-to-recruit responders of the TRacking Adolescents' Individual Lives Survey (TRAILS), a prospective population based cohort study of Dutch (pre)adolescents (at first wave: n = 2230, mean age = 11.09 (SD 0.56), 50.8% girls), with regard to response rates at subsequent measurement waves. Second, easy-to-recruit and hard-to-recruit participants at the fourth TRAILS measurement wave (n = 1881, mean age = 19.1 (SD 0.60), 52.3% girls) were compared with fourth wave non-responders and earlier stage drop-outs on family composition, socioeconomic position (SEP), intelligence (IQ), education, sociometric status, substance use, and psychopathology.
  
  
  RESULTS
  First, over 60% of the hard-to-recruit responders at the first wave were retained in the sample eight years later at the fourth measurement wave. Hard-to-recruit dropouts did not differ from hard-to-recruit retainers. Second, extensive recruitment efforts for the web based survey convinced a population of nineteen year olds with similar characteristics as the hard-to-recruit eleven year olds that were persuaded to participate in a school-based survey. Some characteristics associated with being hard-to-recruit (as compared to being easy-to-recruit) were more pronounced among non-responders, resembling the baseline situation (De Winter et al.2005).
  
  
  CONCLUSIONS
  First, extensive recruitment effort at the first assessment wave of a prospective population based cohort study has long lasting positive effects. Second, characteristics of hard-to-recruit responders are largely consistent across age groups and survey methods.
authors: Interdisciplinary Center Psychopathology and Emotion regulation, University Center for Psychiatry, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands. e.nederhof@umcg.nl
authors: Esther
authors: E
authors: Nederhof
authors: Frederike
authors: F
authors: Jörg
authors: Dennis
authors: D
authors: Raven
authors: René
authors: R
authors: Veenstra
authors: Frank C
authors: FC
authors: Verhulst
authors: Johan
authors: J
authors: Ormel
authors: Albertine J
authors: AJ
authors: Oldehinkel
mesh_terms: D000293:Adolescent; D041923:Adolescent Development / Q000502:physiology*; D002648:Child; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006306:Health Surveys; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology* / Q000503:physiopathology; D009426:Netherlands; D010043:Outcome and Process Assessment, Health Care; D018579:Patient Selection; D010379:Peer Group; D011446:Prospective Studies; D012424:Rural Population; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D014505:Urban Population; D055815:Young Adult