Reproductive factors and fatal hip fractures. A Norwegian prospective study of 63,000 women.
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STUDY OBJECTIVE: The aim of the study was to investigate the impact of reproductive variables (age at menarche, menopause, first and last birth as well as parity, lactation, and abortions) on hip fracture mortality. DESIGN AND SETTING: A prospective study in Norway with more than 60,000 women followed up for 29 years. A total of 465 deaths as a result of hip fracture were recorded. MAIN RESULTS: Statistically significant linear relations (p < or = 0.02) were found between both age at menarche and length of reproductive period (defined as age at menopause to age at menarche) and the mortality of hip fractures in women aged less than 80. The death rate for women with a late menarche (> or = 17 years) was twice that of the women with relatively early menarche (< or = 13 years). Compared with women with less than 30 years between menopause and menarche, the mortality rate ratio in women with more than 38 reproductive years was 0.5. We also found an inverse relation with age at first birth. CONCLUSIONS: This study supports by hypothesis that an early menarche and a long reproductive period protect against hip fracture mortality. High age at first birth may also be protective. (+info)
A prospective study on folate, B12, and pyridoxal 5'-phosphate (B6) and breast cancer.
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To investigate the incidence of breast cancer and prediagnostic serum levels of folate, B12, and pyridoxal 5'-phosphate (B6), we conducted a nested case-control study using resources from the Washington County (Maryland) serum bank. In 1974, 12,450 serum specimens were donated, and in 1989, 14,625 plasma specimens were donated by female residents of Washington County. One hundred ninety-five incident breast cancer cases and 195 controls were matched by age, race, menopausal status at donation, and cohort participation as well as by date of blood donation. In both cohorts and all menopausal subgroups, median B12 concentrations were lower among cases than controls. Differences reached statistical significance only among women who were postmenopausal at donation (1974 cohort, 413 versus 482 pg/ml, P = 0.03; 1989 cohort, 406 versus 452 pg/ml, P = 0.02). Among women postmenopausal at blood donation, observed associations of B12 suggested a threshold effect with increased risk of breast cancer in the lowest one-fifth compared to the higher four-fifths of the control distribution [lowest versus highest fifth: 1974 cohort, matched odds ratio = 4.00 (95% confidence interval = 1.05-15.20); 1989 cohort, matched odds ratio = 2.25 (95% confidence interval = 0.86-5.91)]. We found no evidence for an association between folate, B6, and homocysteine and breast cancer. Findings suggested a threshold effect for serum B12 with an increased risk of breast cancer among postmenopausal women in the lowest one-fifth compared to the higher four-fifths of the control distribution. These results should stimulate further investigations of potentially modifiable risk factors, such as these B-vitamins, for prevention of breast cancer. (+info)
Cigarette smoking and other risk factors in relation to p53 expression in breast cancer among young women.
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p53 mutations may be a fingerprint for cigarette smoking and other environmental carcinogens, including breast carcinogens. This study was undertaken to explore whether p53 mutations are associated with environmental or other suspected or established risk factors for breast cancer. p53 protein detection by immunohistochemistry (which is more easily quantified in large epidemiological studies than are mutations, and are highly correlated with them) was determined for 378 patients from a case-control study of breast cancer. In this population-based sample of women under the age of 45 years, 44.4% (168/378) of the cases had p53 protein detected by immunohistochemistry (p53+). Polytomous logistic regression was used to calculate the odds ratios (ORs) for p53+ and p53- breast cancer, as compared with the controls, in relation to cigarette smoking and other factors. The ratio of the ORs was used as an indicator of heterogeneity in risk for p53+ versus p53- cancer. The ratio of the ORs in a multivariate model was substantially elevated among women with a greater than high school education [2.39; 95% confidence interval (CI), 1.43-4.00], current cigarette smokers (1.96; 95% CI, 1.10-3.52), and users of electric blankets, water beds, or mattresses (1.78; 95% CI, 1.11-2.86). Nonsignificant heterogeneity was noted for family history of breast cancer and ethnicity but not for other known or suspected risk factors. Coupled with the strong biological plausibility of the association, our data support the hypothesis that in breast cancer, as with other tumors, p53 protein immunohistochemical detection may be associated with exposure to environmental carcinogens such as cigarette smoking. (+info)
Breast cancer risk in monozygotic and dizygotic female twins: a 20-year population-based cohort study in Finland from 1976 to 1995.
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This population-based study investigated the occurrence of breast cancer over a 20-year period in a cohort of monozygotic (MZ) and dizygotic (DZ) twins in Finland. Altogether, 13,176 female twins of known zygosity who were living in Finland at the end of 1975 were identified from the Finnish Twin Cohort Study and followed-up for cancer through the Finnish Cancer Registry for the years 1976-1995. Standardized incidence ratios (SIRs) were calculated, based on national cancer incidence rates. The relative risk of breast cancer for MZ twins compared to DZ twins was decreased [SIR(MZ)/SIR(DZ) ratio = 0.78; 95% confidence interval (CI), 0.58-1.0]; the decreased risk for MZ twins (SIR = 0.76; 95% CI, 0.58-1.0) accounted for this result, whereas the risk for DZ twins did not differ from the general population risk (SIR = 0.98; 95% CI, 0.84-1.1). There was no risk decrease among MZ twins in other cancers related to reproductive behavior; i.e., number of children and age at first birth seem not to explain the decreased risk of breast cancer. Our results, which are in line with earlier studies on the same topic, suggest that prenatal influences or postnatal behavioral factors may protect MZ female twins from breast cancer. (+info)
Reproductive characteristics and the age at inception of the perimenopause in a British National Cohort.
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Data from a British national cohort of women born in 1946 were used to investigate the hypothesis that the rate of depletion of oocyte numbers is associated with the age at which a woman reaches the inception of the perimenopause. Menopausal status was obtained using an annual questionnaire, sent to the cohort since the age of 47 years, and risk factor information from contacts with the survey throughout earlier life. Parous women entered the perimenopause later than nulliparous women. Those with the most children had the latest perimenopause, where the estimated hazard ratio for women having four or more children compared with those having none was 0.56 (95% confidence interval 0.39-0.81). Women who had a unilateral oophorectomy reached perimenopause earlier then those who had not (hazard ratio = 1.96, 95% confidence interval 1.15-3.35). There was some evidence that early age at menarche and short menstrual cycles were associated with an earlier perimenopause. No relation was observed with oral contraceptive pill use. Results provided some support for the hypothesis under consideration, while estimates of the median age at inception of the perimenopause due to these factors ranged from 46 to 50 years, which is an important variation with respect to later health. (+info)
The epidemiology of multiple births.
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On the basis of MEDLINE and manual searches, we examined the main papers in the English literature regarding risk factors for spontaneous (i.e. not related to fertility drug use) multiple births. The constant frequency of monozygotic (MZ) pregnancies over time and in different geographical areas suggests that the determination of MZ twins is largely unchanged over time, and that a genetic mechanism may have a role. In contrast, temporal and geographical trends observed in dizygotic (DZ) pregnancies suggest that environmental factors play a role in determining this condition. At present, maternal age and hereditary components are the best-defined determinants for spontaneous multiple births. (+info)
Adolescent reproductive events and subsequent breast cancer risk.
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OBJECTIVES: This study investigated the relationship between reproductive events during adolescence and subsequent breast cancer risk. METHODS: Logistic regression models used self-reported data from 862 case patients and 790 controls in the Carolina Breast Cancer Study. RESULTS: Miscarriage, induced abortion, and full-term pregnancy before 20 years of age were not associated with breast cancer. Among premenopausal women, breast-feeding before 20 years of age was inversely associated with disease. Oral contraceptive use before 18 years of age was positively associated with disease risk among African American women only. CONCLUSIONS: Pregnancy during adolescence does not appear to influence breast cancer risk, but breast-feeding may. A possible increased breast cancer risk among African American women who used oral contraceptives as adolescents warrants further study. (+info)
Reproductive factors of ovarian and endometrial cancer risk in a high fertility population in Mexico.
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A case-control study was carried out in Mexico City during 1995-1997 among women with epithelial ovarian cancer (84 cases) and endometrial cancer (85 cases). The control group consisted of 668 healthy women, matched according to age categories. In a multivariate analysis, the reproductive risk factors for ovarian and endometrial cancer are similar. The risk of ovarian cancer was inversely related to the number of full-term pregnancies; the odds ratio (OR) was 0.17 and the 95% confidence interval (CI) was 0.05-0.54 when comparing nulliparous women versus those with more than seven pregnancies. For endometrial cancer, a similar association was observed (OR, 0.11; 95% CI, 0.04-0.34). The use of oral contraceptive hormones was inversely associated with both ovarian (OR, 0.36; 95% CI, 0.15-0.83) and endometrial cancer risk (OR, 0.36; 95% CI, 0.14-0.90). In women with a history of more than 8.7 years without ovulation, the risk of ovarian cancer decreased four times (OR, 0.23; 95% CI, 0.10-0.50), and that of endometrial cancer decreased more than five times (OR, 0.17; 95% CI, 0.08-0.35). These two neoplasms are clearly typified as hormone dependent, and it is possible to establish that "ovulation" and "exfoliative" mechanisms jointly determine the level of risk for both ovarian and endometrial cancer. (+info)