Prospective study of estrogen replacement therapy and risk of breast cancer in postmenopausal women

Article Abstract:

Data from several lines of investigation indicate that elevated levels of estrogen (a female hormone) are associated with breast cancer. Studies of the role of exogenous estrogen administered to women after menopause (estrogen replacement therapy) have investigated women with histories of estrogen use, but have not distinguished between current and past users. To learn more concerning this issue, data from the Nurses' Health Study were evaluated. The study is a prospective one that involved 121,700 female nurses aged 30 to 55 at its beginning in 1976. In that year, participants answered a questionnaire about risk factors for cancer and cardiovascular disease; follow-up questionnaires were sent in 1978, 1980, 1982 and 1984. Subjects' menopausal status and postmenopausal use of hormones (if applicable) were investigated. The women were classified as current, past, or never users of estrogen replacement therapy, and their breast cancer histories were investigated. Results from 367,187 woman-years of follow-up indicated that approximately 21 percent of this time was taken up by current users; 25 percent by past users; and 51 percent by subjects who had never undergone estrogen replacement therapy (information was missing for 4 percent of the participants). Current users had a relative risk (RR) of 1.36 of developing breast cancer, compared with never-users; past users' RR was 0.98. Factors that could have confounded the results are discussed. Overall, it appears that estrogen promotes the development of breast cancer, but the effect is small. The hormone has a beneficial effect on the risk of cardiovascular disease and hip fractures, which counterbalances its adverse effects on cancer risk. The picture of estrogen's effects is complex, and caution in its use should be observed. (Consumer Summary produced by Reliance Medical Information, Inc.)

Physiological aspects, Statistics, Drug therapy, Menopause, Postmenopausal women, Estrogen, Estrogens

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Prospective study of relative weight, height, and risk of breast cancer

Article Abstract:

Diet and energy intake are known to be associated with the incidence of mammary tumors in laboratory animals. The role of energy balance and body weight, particularly obesity, in the incidence of breast tumors is not clearly known. However, different risk rates obtained from various countries, and from the incidence rate fluctuations of populations who move from one country to another, point to a causal or etiologic role of diet in the development of breast cancer. The height and relative weight of 115,534 women who were 30 to 44 years old at the onset of this long-term study were recorded. At the time of their inclusion into the study all participants were known to be free of breast cancer. Eight years later, 648 premenopausal and 420 postmenopausal women had developed breast cancer. The risk of breast cancer in premenopausal woman was found to be statistically inversely related to their relative weight (weight adjusted for height), a measure of degree of body fat. (Less weight seems to be associated with an increased incidence of breast cancer.) A similar relationship was also found between the patients' weight at 18 years of age (as remembered and reported by the patient) and breast cancer. There was no significant relationship between weight at any age and cancer in postmenopausal women who developed breast cancer. Although thinner women have breast tumors discovered earlier and at a time when they are smaller and have better cure rates, the results in this study do not appear to be biased by such earlier detection. Adult obesity is generally associated with an increase risk of cancer. However, this study suggests that the rate of breast cancer in younger premenopausal woman may be reduced by obesity and that the risks of postmenopausal woman are only slightly affected by obesity.

Obesity

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A prospective study of cigarette smoking and risk of cataract surgery in women

Article Abstract:

Smoking increases the risk of cataracts, most specifically posterior subcapsular cataracts. A study of registered nurses ages 45 to 67 showed that women who smoked at least 65 pack years or greater had 63% increased risk of needing cataract surgery than did nonsmokers. They had 2.5 times the risk of posterior subcapsular cataract, a rare variety which causes symptoms early so making up a disproportionate number of surgical extractions. Risk did not decrease 10 years after quitting. This may be because older cells are compressed toward the center as new cells are produced rather than being replaced. The lens also has a limited ability to repair protein damage. The risk ratio increased by reducing intake of foods eaten with antioxidant vitamins. No studies to date explain if the effect of smoking is due to external smoke irritation or to a smoke constituent absorbed through the lungs.

Prevention, Cataract, Smoking, Cancer prevention, Cataracts

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