The Women's Health Initiative Study (WHI-OS)
Objectives:
Examine the relationship between lifestyle,
socioeconomic, health, and other risk factors with cardiovascular, breast
cancer, colorectal cancer and osteoporotic fracture outcomes. Secondary
objectives include providing more reliable estimates of the extent to which
known risk factors predict disease, more precise estimates of new occurrences
of disease, and to provide a future resource for the identification of new or
novel risk factors especially factors found in blood.
Background:
The Women's Health Initiative (WHI) is a long-term
national health study focusing on strategies for the prevention of
cardiovascular, breast and colorectal cancer and osteoporosis in postmenopausal
women. The WHI study is composed of a randomized clinical trial, community
prevention component, and an observational study. The randomized controlled
clinical trial has three components and eligible women may elect to participate
in one, two or all three of the components. The trial components include
Hormone Replacement Therapy, Dietary Modification, and Calcium/Vitamin D. More
than 68,000 women have been enrolled into the clinical trial component. The
Community Prevention Component is a collaboration between the Centers for
Disease Control and the National Institutes of Health. The purpose of the
Community Prevention Component is to conduct and evaluate health programs that
encourage healthy behaviors.
Subjects:
Participants in the observational study were women
aged 50-79 who were ineligible or unwilling to participate in the clinical
trial component or were recruited through a direct invitation for screening
into the observational study. A total of 93,676 subjects were enrolled in the
observational study. White women comprised 83% of the cohort (78,013), while 8%
were Black (7,639) and 4% Hispanic (2,623). The remaining 5% of the cohort is
comprised of Asian/Pacific Islander, American Indian, and subjects of unknown
race/ethnicity. Many potential participants to the clinical trial component of
the study were already undertaking a low fat diet or were using hormone
replacement therapy and therefore were excluded or declined to participate in
the clinical trial component. These participants were then enrolled into the
observational study. Previous research has demonstrated that at the time of WHI
enrollment, women undertaking hormone replacement therapy and/or low fat diets
generally had healthier lifestyles than those not possessing these behaviors.
The effect of the selection process was that women enrolled in the
observational study tended to have healthier lifestyles compared to those
enrolled in the clinical trial.
Design:
Enrollment in the observational study was conducted
at 40 centers throughout the US and began in September 1993. Recruitment ended
on December 31, 1998. Participants attended a baseline examination and were
re-examined three years later. Participants completed annual updates of
exposures and clinical outcomes. The followup interval is expected to be an
average of approximately seven years.
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Study Website |
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Study Documentation |
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Data Distribution Agreement |
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