title: Blinding decreased recruitment in a prevention trial of postmenopausal hormone therapy.
abstract: OBJECTIVE
  To compare the effect of blind design (active drug and placebo) and nonblind design (active drug and no treatment) on recruitment.
  
  
  METHODS
  A primary prevention trial with postmenopausal hormone therapy in Estonia.
  
  
  METHODS
  Women who were eligible and willing to participate on the basis of the questionnaire survey were randomized into blind and nonblind groups. Recruitment rates are based on record keeping, and reasons for participating were requested in the first-year follow-up.
  
  
  RESULTS
  The recruitment was 30% higher in the nonblind group: of the 4,295 women invited, 37% (95% confidence interval CI=35-39%) in the blind group and 48% (95% CI=46-49%) in the nonblind group were recruited. In both groups, once randomized, most of the losses were women who did not attend the first clinical examination: 49% (blind; 95% CI=47-51%) and 40% (nonblind; 95% CI=38-42%). The rest were found ineligible or lost their interest during clinical examinations. The reasons for joining the trial were relatively similar in the two groups.
  
  
  CONCLUSIONS
  Blinding decreased women's interest in joining a long-term preventive trial. Women's reasons for joining the trial were not influenced by blinding.
authors.affiliation: Health and Social Services, National Research and Development Center for Welfare and Health (STAKES), P.O. Box 220, 00531 Helsinki, Finland. elina.hemminki@stakes.fi
authors.forename: Elina
authors.initials: E
authors.lastname: Hemminki
authors.forename: Sirpa-Liisa
authors.initials: SL
authors.lastname: Hovi
authors.forename: Piret
authors.initials: P
authors.lastname: Veerus
authors.forename: Tiina
authors.initials: T
authors.lastname: Sevón
authors.forename: Risto
authors.initials: R
authors.lastname: Tuimala
authors.forename: Mati
authors.initials: M
authors.lastname: Rahu
authors.forename: Matti
authors.initials: M
authors.lastname: Hakama
mesh_terms: D001290:Attitude; D015914:Estrogen Replacement Therapy; D005260:Female; D006801:Humans; D008875:Middle Aged; D018579:Patient Selection; D016037:Single-Blind Method; D013997:Time Factors