title: Factors associated with participation and attrition in a longitudinal study of bacterial vaginosis in Australian women who have sex with women.
abstract: OBJECTIVE
  A number of social and sexual risk factors for bacterial vaginosis (BV) have been described. It is important to understand whether these factors are associated with non-participation or attrition of participants from longitudinal studies in order to examine potential for recruitment or attrition bias. We describe factors associated with participation and attrition in a 24-month prospective cohort study, investigating incident BV among Australian women who have sex with women.
  
  
  METHODS
  Participants negative for prevalent BV were offered enrolment in a longitudinal cohort study. Participants self-collected vaginal samples and completed questionnaires 3-monthly to endpoint (BV-positive/BV-negative by 24 months). Factors associated with participation in the cohort study were examined by logistic regression and factors associated with attrition from the cohort were examined by Cox regression.
  
  
  RESULTS
  The cross-sectional study recruited 457 women. 334 BV-negative women were eligible for the cohort and 298 (89%, 95%CI 85, 92) enrolled. Lower educational levels (aOR 2.72, 95%CI 1.09, 6.83), smoking (aOR 2.44, 95%CI 1.13, 5.27), past BV symptoms (aOR 3.42, 95%CI 1.16, 10.10) and prior genital warts (aOR 2.71, 95%CI 1.14, 6.46) were associated with non-participation; a partner co-enrolling increased participation (aOR 3.73, 95%CI 1.43, 9.70). 248 participants (83%, 95%CI 78, 87) were retained to study endpoint (BV-negative at 24 months or BV-positive at any stage). Attrition was associated being <30 yrs (aHR 2.15, 95%CI 1.13, 4.10) and a male partner at enrolment (aHR 6.12, 95%CI 1.99, 18.82).
  
  
  CONCLUSIONS
  We achieved high participation and retention levels in a prospective cohort study and report factors influencing participation and retention of participants over a 24-month study period, which will assist in the design and implementation of future cohort studies in sexual health and disease.
authors.affiliation: Melbourne Sexual Health Centre, Alfred Health, Carlton, Victoria, Australia; Melbourne School of Population and Global Health, The University of Melbourne, Carlton, Victoria, Australia.
authors.forename: Dana S
authors.initials: DS
authors.lastname: Forcey
authors.affiliation: Melbourne Sexual Health Centre, Alfred Health, Carlton, Victoria, Australia; Melbourne School of Population and Global Health, The University of Melbourne, Carlton, Victoria, Australia.
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Walker
authors.affiliation: Melbourne Sexual Health Centre, Alfred Health, Carlton, Victoria, Australia; Melbourne School of Population and Global Health, The University of Melbourne, Carlton, Victoria, Australia.
authors.forename: Lenka A
authors.initials: LA
authors.lastname: Vodstrcil
authors.affiliation: Melbourne Sexual Health Centre, Alfred Health, Carlton, Victoria, Australia; Central Clinical School, Monash University, The Alfred Centre, Melbourne, Victoria, Australia.
authors.forename: Christopher K
authors.initials: CK
authors.lastname: Fairley
authors.affiliation: Melbourne Sexual Health Centre, Alfred Health, Carlton, Victoria, Australia; Central Clinical School, Monash University, The Alfred Centre, Melbourne, Victoria, Australia.
authors.forename: Jade E
authors.initials: JE
authors.lastname: Bilardi
authors.affiliation: The Kirby Institute, The University of New South Wales, Darlinghurst, New South Wales, Australia.
authors.forename: Matthew
authors.initials: M
authors.lastname: Law
authors.affiliation: Melbourne School of Population and Global Health, The University of Melbourne, Carlton, Victoria, Australia.
authors.forename: Jane S
authors.initials: JS
authors.lastname: Hocking
authors.affiliation: Melbourne Sexual Health Centre, Alfred Health, Carlton, Victoria, Australia.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Fethers
authors.affiliation: Melbourne Sexual Health Centre, Alfred Health, Carlton, Victoria, Australia.
authors.forename: Susan
authors.initials: S
authors.lastname: Petersen
authors.affiliation: Melbourne Sexual Health Centre, Alfred Health, Carlton, Victoria, Australia.
authors.forename: Clare
authors.initials: C
authors.lastname: Bellhouse
authors.affiliation: Melbourne Sexual Health Centre, Alfred Health, Carlton, Victoria, Australia; Central Clinical School, Monash University, The Alfred Centre, Melbourne, Victoria, Australia.
authors.forename: Marcus Y
authors.initials: MY
authors.lastname: Chen
authors.affiliation: Melbourne Sexual Health Centre, Alfred Health, Carlton, Victoria, Australia; Melbourne School of Population and Global Health, The University of Melbourne, Carlton, Victoria, Australia; Central Clinical School, Monash University, The Alfred Centre, Melbourne, Victoria, Australia.
authors.forename: Catriona S
authors.initials: CS
authors.lastname: Bradshaw
mesh_terms: D000293:Adolescent; D000328:Adult; D001315:Australia / Q000453:epidemiology; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003710:Demography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D012307:Risk Factors; D012725:Sexual Behavior; D012747:Sexual Partners; D012907:Smoking; D011795:Surveys and Questionnaires; D016585:Vaginosis, Bacterial / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D014860:Warts / Q000150:complications / Q000473:pathology; D055815:Young Adult