title: Improving retention of very old participants in longitudinal research: experiences from the Newcastle 85+ study.
abstract: BACKGROUND
  People aged 85 and over are often excluded from research on the grounds of being difficult to recruit and problematic to retain. The Newcastle 85+ study successfully recruited a cohort of 854 85-year-olds to detailed health assessment at baseline and followed them up over 3 phases spanning 5 years. This paper describes the effectiveness of its retention strategies.
  
  
  METHODS
  Primary retention strategies involved meticulous management of contact information and active maintenance of contact with participants between research visits and between phases of the study. For statistical analysis, data on post-inclusion attrition over the 3 follow-up phases was separated into 'death' and 'withdrawal' categories, with sub-categories 'health' and 'non-health' reasons created for 'withdrawal'. Multinomial logistic regression was used to determine if particular socio-demographic and health characteristics were associated with post-inclusion attrition due to withdrawal at each of the 3 phase-to-phase transition points.
  
  
  RESULTS
  For both sexes, at successive follow-up phases there was a decrease in attrition due to withdrawal and an increase due to death. Withdrawal was most prevalent between baseline and phase 2. Across the 5 years of the study total post-inclusion (post-baseline) attrition due to death accounted for a 40% (344/854) loss to cohort and total post-inclusion attrition due to withdraw a 19% (166/854) loss to cohort, with health reasons for withdrawal becoming more dominant over time. Adjusting for sex, parsimonious modelling showed only occupational class (National Statistics Socio-economic Classification) to be associated with withdrawal and only between baseline and phase 2 (routine/manual compared to managerial (OR 3.41; 95% CI [1.23 to 9.44]).
  
  
  CONCLUSIONS
  Following successful recruitment, we retained a high proportion of participants from a very old age group over 5 years of longitudinal research. No strong predictors of post-inclusion attrition due to withdrawal were found, suggesting the general effectiveness of our retention strategies.
authors.affiliation: Newcastle University Institute for Ageing, Campus for Ageing and Vitality, Newcastle upon Tyne, United Kingdom; Institute of Health and Society, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Karen
authors.initials: K
authors.lastname: Davies
authors.affiliation: Newcastle University Institute for Ageing, Campus for Ageing and Vitality, Newcastle upon Tyne, United Kingdom; Institute of Health and Society, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Andrew
authors.initials: A
authors.lastname: Kingston
authors.affiliation: Newcastle University Institute for Ageing, Campus for Ageing and Vitality, Newcastle upon Tyne, United Kingdom; Institute of Health and Society, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Louise
authors.initials: L
authors.lastname: Robinson
authors.affiliation: Newcastle University Institute for Ageing, Campus for Ageing and Vitality, Newcastle upon Tyne, United Kingdom.
authors.forename: Joan
authors.initials: J
authors.lastname: Hughes
authors.affiliation: Newcastle University Institute for Ageing, Campus for Ageing and Vitality, Newcastle upon Tyne, United Kingdom.
authors.forename: Judith M
authors.initials: JM
authors.lastname: Hunt
authors.affiliation: Newcastle University Institute for Ageing, Campus for Ageing and Vitality, Newcastle upon Tyne, United Kingdom.
authors.forename: Sally A H
authors.initials: SA
authors.lastname: Barker
authors.affiliation: Newcastle University Institute for Ageing, Campus for Ageing and Vitality, Newcastle upon Tyne, United Kingdom.
authors.forename: June
authors.initials: J
authors.lastname: Edwards
authors.affiliation: Newcastle University Institute for Ageing, Campus for Ageing and Vitality, Newcastle upon Tyne, United Kingdom; Institute of Health and Society, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Joanna
authors.initials: J
authors.lastname: Collerton
authors.affiliation: Newcastle University Institute for Ageing, Campus for Ageing and Vitality, Newcastle upon Tyne, United Kingdom; Institute of Health and Society, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Carol
authors.initials: C
authors.lastname: Jagger
authors.affiliation: Newcastle University Institute for Ageing, Campus for Ageing and Vitality, Newcastle upon Tyne, United Kingdom; Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne, United Kingdom.
authors.forename: Thomas B L
authors.initials: TB
authors.lastname: Kirkwood
mesh_terms: D000367:Age Factors; D000369:Aged, 80 and over; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D018579:Patient Selection; D012106:Research