The Clinical Trial (CT) and Observational Study
(OS) components of the WHI are interrelated and have
been conducted at the
same 40 clinical centers.
The Clinical Trial (CT) and Observational Study
(OS) scientifically sought answers to the long-waited questions on the
benefits and risks of hormone therapy, changes in dietary patterns
and calcium/vitamin D supplementation in disease prevention. The WHI CT/OS
activities were performed at 40 clinical centers located throughout
the United States. These clinical centers were funded through the contract
mechanism. A single coordinating center, at the Fred Hutchinson Cancer Research
Center, managed data collection and analysis.
The CT/OS included a five-year recruitment period, which
began in September 1993, and ended December 31, 1998, with a planned average of
eight years of follow-up, and two years for data analysis.
Clinical Trial (CT)
The randomized controlled clinical trial (CT) component of
the WHI enrolled 68,131 postmenopausal women 50 to79 years of age. This
trial had three interventions and women could enroll in one or more of the
intervention components.
The expected enrollment numbers for each component of the
clinical trial was as follows:
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The HORMONE THERAPY (HT) component examined the effect of hormonal
therapy on prevention of coronary heart disease and osteoporotic fractures.
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The DIETARY MODIFICATION (DM)
component evaluated the effect of a low-fat dietary pattern on prevention
of breast and colon cancer and coronary heart disease.
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The CALCIUM/VITAMIN D
SUPPLEMENTATION (CaD) component evaluated the effect of calcium and
vitamin D supplementation on prevention of osteoporotic fractures and colon
cancer. Women became eligible to join this component of the trial after being
enrolled in either the Hormone Therapy (HT), Dietary
Modification (DM) or both components for at 1 year.
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Primary/Secondary Outcomes and
Possible Adverse Effects
The primary and secondary outcomes and possible adverse
effects for the clinical trial at the time of the study
design are listed in the table below:
Clinical Trial Outcomes and Possible
Adverse Effects
|
HT |
CaD |
DM |
Primary Outcome |
Coronary Heart Disease |
Hip Fractures |
Breast Cancer, Colorectal Cancer |
Secondary Outcome |
Hip and Other Fractures |
Colorectal Cancer, Combined Fractures |
Coronary Heart Disease |
Possible Adverse Effects |
Breast Cancer and Venous Thrombosis |
Renal Stones |
Nutritional Deficiencies (None Known) |
HT = Hormone Therapy
DM = Dietary Modification CaD = Calcium and Vitamin
D Supplementation |
There were no known
possible adverse effects for participation in the dietary modification (DM)
components of the WHI clinical trial.
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Observational Study
Women who were ineligible or unwilling to participate in the
clinical trial were offered the opportunity to enroll in a concurrent long-term
observational study (OS). This study sought to:
- delineate new risk factors and biological markers for
diseases in women,
- allow comparison with the WHI clinical trial cohort
findings,
- evaluate temporal relationship between risk factors and
disease outcomes, and
- improve estimates of known predictors of disease by
sociodemographic factors.
There were 93,676 women who joined this part of the study.
Recruitment, follow-up and analysis for the OS was concurrent with the CT.
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