title: Effect of stamped reply envelopes and timing of newsletter delivery on response rates of mail survey: a randomised controlled trial in a prospective cohort study.
abstract: OBJECTIVE
  To examine the effects of stamped reply envelope and the timing of newsletter distribution.
  
  
  METHODS
  A randomised controlled trial in a prospective cohort study with a 2×2 factorial design of two interventions.
  
  
  METHODS
  The Japan Nurses' Health Study (JNHS), a prospective cohort study for women's health.
  
  
  METHODS
  The present study included 6938 women who were part of the first-year entry cohort for the fifth wave of the biannual follow-up survey of the JNHS.
  
  
  METHODS
  The participants were randomly allocated into four groups; Group-1 (business-reply, newsletter with initial mailing), Group-2 (business-reply, newsletter with reminder), Group-3 (stamped envelopes, newsletter with initial mailing) and Group-4 (stamped envelopes, newsletter with reminder). The thank-you and reminder letters were mailed out at the end of the sixth week. This study was censored at the end of 12 weeks.
  
  
  METHODS
  Main outcome measures were cumulative response at the end of 6 and 12 weeks after mailing out the questionnaire.
  
  
  RESULTS
  The cumulative response at 12 weeks were 58.3% for Group-1, 54.1% for Group-2, 60.5% for Group-3 and 56.7% for Group-4 (p=0.001). The odds of the response was higher for stamped envelopes than for business-reply envelopes (OR (95% CI)=1.10(1.00 to 1.21)). The odds was higher for newsletter delivery with initial mailing than for with reminder (1.18(1.07 to 1.29)). The response in first 6 weeks for stamped envelope was significantly higher than for business-reply envelope (p=0.047). Although the response in 6 weeks for women received the newsletter with initial mailing was lower than for women who did not, the proportions did not differ significantly (p=0.291).
  
  
  CONCLUSIONS
  The style of return envelope affected response rates of mail survey. The results of this study suggest that practices of provision of the additional information, should be handled individually in advance, as a separate event from sending follow-up questionnaire or reminder letters.
authors.affiliation: Department of Basic Medical Sciences, School of Health Sciences, Gunma University, Maebashi, Gunma, Japan.
authors.forename: Chizuko
authors.initials: C
authors.lastname: Wakabayashi
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Hayashi
authors.forename: Kazue
authors.initials: K
authors.lastname: Nagai
authors.forename: Naoko
authors.initials: N
authors.lastname: Sakamoto
authors.forename: Yoko
authors.initials: Y
authors.lastname: Iwasaki