Primary* and Subsidiary** Hypotheses of the Women's Health Initiative Clinical Trial
Dietary Modification Branch (DM):
* DM–in the form of a low-fat dietary pattern (reduced intake of total fat and saturated fat, increased intake of complex carbohydrate and fiber-containing foods)–will reduce the incidence of breast cancer and colorectal cancer, separately.
** DM will reduce the incidence of coronary heart disease.
Hormone Replacement Therapy Branch (HRT):
* Estrogen replacement therapy (ERT) and/or progestin and estrogen replacement therapy (PERT) will reduce the incidence of coronary heart disease and of other cardiovascular disease.
** ERT and/or PERT will reduce the incidence of all osteoporosis-related fractures and hip fractures, separately.
** ERT will increase the incidence of endometrial and breast cancer.
** PERT will increase the incidence of breast cancer.
Calcium and Vitamin D Supplementation Branch (CaD):
* CaD will reduce the incidence of hip fractures.
** CaD will reduce the incidence of colorectal cancer.
Some combinations of the treatments may have synergistic effects, while others may cancel out each other's effects. In addition, benefit or risk may also relate to some baseline
Source: Adapted from National Institute of Health's WHI Protocol, June 28, 1993, p. 28.
characteristic of the participants. The WHI will generally lack sufficient power to test these subgroup hypotheses unless there are unexpectedly large effects. However, subgroup analyses will be performed to examine:
The effect of DM plus HRT on breast cancer incidence in women at high and low risk of breast cancer.
The effect of DM plus HRT on the incidence of coronary and other cardiovascular disease and breast cancer, compared with each therapy alone.
The effect of HRT on the incidence of coronary and other cardiovascular disease in women with and without cardiovascular disease at baseline.
The effect of HRT on the incidence of coronary and other cardiovascular disease and breast cancer in obese and lean women.
The effect of ERT on the incidence of coronary and other cardiovascular disease among women with and without a uterus.
The effect of HRT plus CaD on fracture rates, compared with each therapy alone.
The effect of CaD on fractures and colorectal cancer in women with lower and higher intakes of dietary calcium.
The effect of DM, HRT, and CaD in subgroups of women defined by age and race/ethnicity.
The CT will also offer an opportunity to examine a number of other pertinent factors, including the following:
The effect of each treatment on perceived quality of life, on combined primary and secondary endpoints, and on total mortality.
The effects of DM and HRT on lipids, lipoproteins, clotting factors, blood pressure, body mass index, waist-to-hip ratio, and blood glucose.
Trends in the magnitude of DM, HRT, and CaD effects across age categories and across values of other participant characteristics.
The relationship to clinical outcomes of (a) baseline biochemical and physical variables, (b) changes in those variables induced by treatment, and (c) adherence.
The effect of the treatments on a variety of subsidiary endpoints, such as other cancers (ovarian, endometrial), diabetes mellitus, and other age-related outcomes.