title: Consequences of an Extended Recruitment on Participation in the Follow-Up of a Child Study: Results from the German IDEFICS Cohort.
abstract: Declining response proportions in population-based studies are often countered by extended recruitment efforts at baseline that may, however, result in higher attrition in a subsequent follow-up. This study analysed the effect of extended recruitment efforts on attrition at the first follow-up of a child cohort.
  
  
  
  We used paradata (i.e. information about the process of data collection) from the German IDEFICS cohort investigating dietary- and life style-induced health effects on children to quantify recruitment effort and classify respondents as completing the recruitment early vs. late for baseline and follow-up separately. Multilevel logistic regression models were used to investigate the association between recruitment effort and attrition at follow-up (loss to follow-up) adjusted for sociodemographic and health related variables.
  
  
  
  Individuals who were late respondents at baseline and early respondents at the follow-up had a higher chance of attrition (odds ratio 1.65, 95% confidence interval (CI) 1.19, 2.28) as compared to other groups. An investigation of reasons for non-participation revealed that members of this group were more likely to be not reachable by phone.
  
  
  
  An extended recruitment effort at baseline of a child cohort study is not per se associated with a higher chance of attrition at follow-up. Much care should be taken to collect valid telephone numbers.
authors.affiliation: Leibniz Institute for Prevention Research and Epidemiology - BIPS, Bremen, Germany.
authors.forename: Malte
authors.initials: M
authors.lastname: Langeheine
authors.affiliation: Leibniz Institute for Prevention Research and Epidemiology - BIPS, Bremen, Germany.
authors.forename: Hermann
authors.initials: H
authors.lastname: Pohlabeln
authors.affiliation: Leibniz Institute for Prevention Research and Epidemiology - BIPS, Bremen, Germany.|Institute of Statistics, Faculty of Mathematics and Computer Science, University Bremen, Bremen, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Ahrens
authors.affiliation: Leibniz Institute for Prevention Research and Epidemiology - BIPS, Bremen, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Rach
mesh_terms: D002648:Child; D002675:Child, Preschool; D005260:Female; D005500:Follow-Up Studies; D005858:Germany; D006306:Health Surveys; D006801:Humans; D007258:Informed Consent; D008297:Male; D010349:Patient Compliance / Q000706:statistics & numerical data*; D010358:Patient Participation / Q000706:statistics & numerical data*; D018579:Patient Selection
keywords: 
  IDEFICS
  ; late respondents; loss to follow-up; paradata