Design & Protocol

The Women’s Health Initiative consists of two major parts: a set of randomized Clinical Trials and an Observational Study. The WHI Clinical Trials (CT) (n=68,132) includes three overlapping components, each a randomized controlled comparison among women who were postmenopausal and aged 50-79 at randomization. The three CT components are: Dietary Modification (DM) Trial, Hormone Therapy (HT) Trials, and Calcium and Vitamin D (CaD) Trial. Women who were not willing or eligible to join the CT were invited to join the Observational Study (OS). Eligible women were allowed to join one, two, or all three clinical trials, but could not participate in both a clinical trial and the OS.

For more specific details about the design and protocol of the WHI trials and extension studies, please refer to the Protocols and Study Consents page and WHI Study Manuals.

Recruitment

Recruitment for the WHI began in 1993 and ended in 1998 and was conducted by 40 Clinical Centers in 24 states and the District of Columbia. Enrollment of racial/ethnic minority groups proportionate to the total minority population of women between 50 and 79 years of age was a high priority of the WHI. At the end of the recruitment period, 161,808 women had joined the WHI, with about 17% representing racial/ethnic minority groups.

Recruitment efforts occurred on a local level at the Clinical Centers and on a national level at the National Institutes of Health, the Clinical Coordinating Center, and various study-wide committees. Most Clinical Centers used multiple recruitment strategies, with mass mailings being the primary method of identifying potential participants for screening.

Recruitment efforts are described in greater detail in WHI Study Manuals, Vol. 2 - Section 3: Recruitment.

Screening & Enrollment

Eligibility was defined generally for all WHI components with component-specific exclusion criteria. At the time of enrollment, all women were required to be between 50 and 79 years old, postmenopausal, and intending to reside in the area for at least 3 years. Table 1 – WHI Inclusion and Exclusion Criteria in the Baseline Recruitment Monograph presents the specific criteria for the three Clinical Trial (CT) components and the Observational Study (OS).

To ensure sufficient representation of all age groups, age distribution goals were specified for the CT. For HT and DM, each WHI Clinical Center had specific recruitment goals stratified by age group, study component, and, for HT, hysterectomy status. When the recruitment goal for a particular age range and trial was met, women in that age range could no longer be randomized to that trial.

For more information on Screening & Enrollment, see WHI Study Manuals, Vol. 2 - Section 4: Screening.