Women's Interview Study of Health
The Women's Interview Study of Health (WISH), a population-based case-control study conducted during the early 1990s, focused on identifying risk factors for early onset breast cancers. The study was conducted by NCI and included newly diagnosed breast cancer patients from the SEER areas of Atlanta and Seattle and from ten counties of central New Jersey. Given the relatively young age of study participants, a major focus of the study was on factors early in life that might be predictive of the subsequent occurrence of breast cancer. These included use of oral contraceptives (OCs), developmental history, physical activity, diet (including alcohol consumption), and cigarette smoking. The study also addressed the role of pre- and postnatal factors that have been postulated to have an effect on subsequent breast cancer risk.
Results from the study showed that recent use of OCs, especially long-term use, increased the risk of very early breast cancers, namely those that develop prior to the age of 35. Notably, recent OC users who had been exposed for 10 or more years were at approximately a twofold increased risk compared with nonusers. An analysis of the dose of estrogens and progestins used provided support for the notion that the elevated risks may have been due to the higher formulations that were used in early years. Alcohol consumption also was identified as a major predictor of risk, although early life exposures were no more predictive of risk than were later exposures. Although body size was found to be predictive of risk, components of diet and physical activity could not be linked definitely with this relationship.
This study provided support for the notion that very early life exposures have an effect on subsequent breast cancer risk. Notably, twins – particularly women with a twin brother – were at an increased risk compared to singletons, a finding that is consistent with the observation of high estrogen levels in dizygotic twin pregnancies. In addition, a reduced breast cancer risk was observed among women who had been breastfed as infants. This finding requires further exploration, including an underlying biologic explanation.
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