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PubMed1997

Trends in the incidence rate and risk factors for breast cancer in Japan.

The incidence rate of breast cancer in Japan rose more than two-fold from 1959-60 to 1983-87. To assess to what extent this increase can be explained by changes in the prevalence of four major risk factors of breast cancer (i.e. age at menarche, age at first birth, age at menopause, and parity), we estimated the probability of developing breast cancer based on the joint distribution and relative risks of these four risk factors. The age-specific incidence rate during 1959-60 reported by the Miyagi Prefectural Cancer Registry was used to estimate the baseline hazard rate for women without the four risk factors in the same age group. Assuming that the baseline hazard rate is constant during all periods, we calculated the expected incidence rates during the periods of 1959-60, 1962-64, 1968-71, 1973-77, 1978-81, and 1983-87 for each age group. Large discrepancies were noted between the observed and expected incidence rates during 1983-87 in all age groups. The change in the joint distribution of the four risk factors accounted for less than 40% of the increase observed from 1959-60 to 1983-87, suggesting the effects of other powerful risk factors.

Adult↗
PubMed1999

The relation of breast size to breast cancer risk in postmenopausal women (United States).

OBJECTIVE: Breast size has been hypothesized to predict a woman's risk of breast cancer although studies in the main have not supported an association. In a large, population-based case-control study we examined whether breast size might emerge as a significant risk factor among very lean women in whom breast size might be a truer reflection of the volume of gland mass at risk for malignant change. METHODS: The data derive from a population-based case-control study of women aged 50 to 79 years conducted in several New England states and Wisconsin. Incident cases of invasive breast cancer (n = 2015) were identified through state tumor registries and controls (n = 2556) were selected at random within age strata from population lists. Telephone interviews were conducted to obtain information on known and suspected risk factors which included bra dimensions (cup and back size) prior to a first birth, or at the age of 20 for nulliparous women. RESULTS: We observed a significant positive association for cup size which was limited to women who were the most lean as young adults based on chest circumference. Among those reporting a chest size under 34 inches multivariate-adjusted relative risks were 1.34 (95% CI: 1.04 to 1.74) for cup size B, and 1.76 (95% CI: 1.04 to 3.01) for cup size C and larger, compared to a cup size smaller than B, and the trend for increasing cup size was statistically significant (P = 0.005). There was no relation with breast size among women reporting an average or larger back circumference (34 inches or larger). CONCLUSION: Breast size before a pregnancy is a positive predictor of postmenopausal breast cancer, but this association is limited to those who were especially lean as young women.

Adipose Tissue↗
PubMed1998

Association of family history and other risk factors with breast cancer risk (Sweden).

OBJECTIVES: Women with a family history of breast cancer have an increased risk for the disease. However, the combined impact of family history and other risk factors on breast cancer risk is unclear. We conducted a large epidemiologic study to examine this issue. METHODS. In a population-based case-control study in all of Sweden, 3,345 women aged 50 to 74 years with invasive breast cancer (84 percent of all eligible), and 3,454 controls of similar age (82 percent of all selected) were included. Mailed questionnaires and telephone interviews were used to collect detailed information on potential breast cancer risk factors. Odds ratios (OR) and 95 percent confidence intervals (CI) were estimated through multiple logistic regression. RESULTS: Women with a history of breast cancer in any first-degree relative had an increased risk of breast cancer compared with those without such a history (OR = 1.96, CI = 1.67-2.30). There was no clear indication of a differential impact of hormonal risk factors (age at menarche, parity, age at first birth, age at menopause, use of exogenous hormones, and weight gain) or body build at age seven among women with and without a positive family history. Yet, benign breast disease and height clearly were related to breast cancer risk in subjects without a family history, whereas seemingly not so in women with a family history. Formal tests for interaction between family history and these factors, however, did not prove statistically significant. CONCLUSIONS: Our findings indicate that established risk factors entail similar associations with breast cancer risk among women with and without family history of the disease.

Aged↗
PubMed1999

A pooled analysis of case-control studies of thyroid cancer. III. Oral contraceptives, menopausal replacement therapy and other female hormones.

OBJECTIVE: The relations between oral contraceptives (OC), hormone replacement therapy (HRT) for menopause, and other female hormone use and thyroid cancer risk was analyzed using the original data from 13 studies from North America, Asia and Europe. METHODS: Based on 2,132 cases and 3,301 controls, odds ratios (OR) and the corresponding 95% confidence intervals (CI) were obtained by conditional regression models, conditioning on study and age at diagnosis, and adjusting for age, radiation exposure and parity. RESULTS: Overall, 808 (38%) cases versus 1,290 (39%) controls had ever used OCs, corresponding to an OR of 1.2 (95% CI 1.0 to 1.4). There was no relation with duration of use, age at first use, or use before first birth. The OR was significantly increased for current OC users (OR = 1.5, 95% 1.0 to 2.1), but declined with increasing time since stopping (OR = 1.1 for > 10 years since stopping). The association was stronger for papillary cancers (OR = 1.6 for current users) than for other histologic types. No significant heterogeneity was observed across studies or geographic areas. Eight studies had data on HRT, for a total of 1,305 cases and 2,300 controls: 110 (8%) cases and 205 (9%) controls reported ever using HRT (OR = 0.8; 95% CI 0.6 to 1.1). The ORs were 1.6 (95% to 0.9 to 2.9) for use of fertility drugs, and 1.5 (95% CI 1.1 to 2.1) for lactation suppression treatment. CONCLUSIONS: The studies considered in these analyses include most of the epidemiological data on the role of exogenous hormone use in the etiology of thyroid cancer, and they provide reassuring evidence on the absence of an association of practical relevance. The moderate excess risk in current OC users, if not due to increased surveillance for thyroid masses among OC users, is similar to that described for breast cancer, and would imply a role of female hormones on thyroid cancer promotion. There was no indication of increased thyroid cancer risk 10 or more years after discontinuing OC use.

Adenocarcinoma, Papillary↗
PubMed2000

Association of mammographically defined percent breast density with epidemiologic risk factors for breast cancer (United States).

OBJECTIVE: Mammographically defined percent breast density is an important risk factor for breast cancer, but the epidemiology of this trait is poorly understood. Although several studies have investigated the associations between reproductive factors and density, few data are available on the associations of breast density and waist-to-hip ratio (WHR), physical activity, education, alcohol and smoking. METHODS: We investigated the associations of known and suspected breast cancer risk factors with breast density in a large breast cancer family study. Information was collected on members of 426 families through telephone interviews, mailed questionnaires and mammography. Mammographic films on 1900 women were digitized and breast density was estimated in discrete five-unit increments by one radiologist. Analysis of covariance techniques were used and all analyses were performed stratified by menopausal status. RESULTS: Similar to other reports, nulliparity, late age at first birth, younger age and lower body mass index were associated with increased percent density in both premenopausal and postmenopausal women, and hormone replacement therapy among postmenopausal women. Higher levels of alcohol consumption and low WHR were associated with increased percent density among both premenopausal and postmenopausal women (differences of 3-11% between high and low categories). However, smoking and education were inversely associated with percent density among premenopausal (p = 0.004 and p = 0.003, respectively) but not postmenopausal women (p = 0.52 and p = 0.90). Physical activity was not associated with percent density in either stratum (p values > 0.25). Combined, these factors explained approximately 37% of the variability in the percent density measure in premenopausal women and 19% in postmenopausal women. CONCLUSIONS: Many of these factors may potentially affect breast cancer risk through their effect on percent breast density.

Adult↗
PubMed2000

The effect of physical activity on breast cancer risk: a cohort study of 30,548 women.

BACKGROUND: In epidemiological studies abundant physical activity has been related to decreased breast cancer risk, though the results have been inconsistent. The purpose of this paper was to study the association of physical activity at leisure and commuting to work and incidence of breast cancer. METHODS: The study cohort consisted of 30,548 female participants of the Finnish adult health behaviour survey, based on annual random samples of Finns aged 15-64, collected in 1978-1993. By the end of 1995, 332 breast cancer cases had been diagnosed in the cohort. Relative risks of breast cancer were adjusted for age at survey, body mass index (BMI), education, length of follow-up, parity and age at first birth using Poisson regression models. RESULTS: Compared to women exercising less than once a week, the adjusted relative risk of breast cancer for women exercising once a week was 0.80 (95% confidence interval (CI): 0.58-1.10), for women exercising 2-3 times per week 0.92 (95% CI: 0.78-1.22) and for women exercising daily 1.01 (95% CI: 0.72-1.42). Women who reported commuting, walking or bicycling to work 30 min or more daily had slightly lower adjusted risk of breast cancer (RR: 0.87, 95% CI: 0.62-1.24) than women working at home, being unemployed or driving a car to working place. CONCLUSION: Although a small protective effect of regular physical activity for breast cancer incidence was found in physical activity when commuting to work, the role of the physical activity in breast cancer prevention is still an open question.

Adolescent↗
PubMed2002

Risk factors for medullary thyroid carcinoma: a pooled analysis.

OBJECTIVE: To investigate risk factors for medullary thyroid cancer (MTC). METHODS: We conducted a pooled analysis of 14 case-control studies from Europe, North America, and Asia, including 67 medullary cancers (43 women and 24 men) diagnosed in ten studies. Of the original 4776, we selected five controls per case matched on study, gender, and age. The pooled odds ratios (OR) were estimated using conditional logistic regression. RESULTS: Education, weight, and body mass were not associated with MTC, but a significant positive relationship was seen with height (OR = 2.6 for highest vs lowest tertile). Significant excess risks were associated with a history of thyroid nodules (OR = 12), hypertension (OR = 2.3), gallbladder disease (OR = 4.3), and allergies (OR = 2.2). Among current smokers, a decreased risk of MTC was observed with increasing number of cigarettes. The risk was significantly elevated among women having a first birth after age 25 years, but no clear pattern emerged for other reproductive factors. CONCLUSIONS: Although the number of MTC was small, we detected several significant associations, including prior thyroid and other diseases.

Adult↗
PubMed2002

The Long Island Breast Cancer Study Project: description of a multi-institutional collaboration to identify environmental risk factors for breast cancer.

The Long Island Breast Cancer Study Project is a federally mandated, population-based case-control study to determine whether breast cancer risk among women in the counties of Nassau and Suffolk, NY, is associated with selected environmental exposures, assessed by blood samples, self-reports, and environmental home samples. This report describes the collaborative project's background, rationale, methods, participation rates, and distributions of known risk factors for breast cancer by case-control status, by blood donation, and by availability of environmental home samples. Interview response rates among eligible cases and controls were 82.1% (n = 1,508) and 62.8% (n = 1,556), respectively. Among case and control respondents who completed the interviewer-administered questionnaire, 98.2 and 97.6% self-completed the food frequency questionnaire; 73.0 and 73.3% donated a blood sample; and 93.0 and 83.3% donated a urine sample. Among a random sample of case and control respondents who are long-term residents, samples of dust (83.6 and 83.0%); soil (93.5 and 89.7%); and water (94.3 and 93.9%) were collected. Established risk factors for breast cancer that were found to increase risk among Long Island women include lower parity, late age at first birth, little or no breast feeding, and family history of breast cancer. Factors that were found to be associated with a decreased likelihood that a respondent would donate blood include increasing age and past smoking; factors associated with an increased probability include white or other race, alcohol use, ever breastfed, ever use of hormone replacement therapy, ever use of oral contraceptives, and ever had a mammogram. Long-term residents (defined as 15+ years in the interview home) with environmental home samples did not differ from other long-term residents, although there were a number of differences in risk factor distributions between long-term residents and other participants, as anticipated.

Adult↗
PubMed1997

Induced and spontaneous abortion in relation to risk of breast cancer (United States).

The relation of induced and spontaneous abortion to the risk of breast cancer is evaluated in a hospital-based case-control interview study conducted in three cities in the United States from 1985 through 1995. Cases were 1,803 women aged 25 to 64 years with newly diagnosed invasive breast cancer; controls were 4,182 women of the same ages admitted for conditions unrelated to reproductive factors. Other breast cancer risk-factors were controlled through multiple logistic regression. The reference for all analyses was women who had never had an abortion, either induced or spontaneous. Among parous women, the relative risk (RR) estimate was 1.1 (95 percent confidence interval [CI] = 0.9-1.5) for induced abortion overall, 1.0 (CI = 0.7-1.4) for abortion before the first birth, and 1.3 (CI = 1.0-1.8) for abortion after at least one birth. Among nulliparous women, the relative risk estimate for induced abortion was 1.3 (CI = 0.9-1.9). There was no trend of increased risk with number of abortions, nor was there consistent evidence of an increased risk in any particular subgroup. Spontaneous abortion was not associated with increased risk of breast cancer, either among nulliparous women or among parous women. These findings provide little support for the hypothesis that induced abortion increases breast cancer risk overall or in particular subgroups.

Abortion, Induced↗
PubMed2002

High breast cancer incidence rates among California teachers: results from the California Teachers Study (United States).

OBJECTIVE: [corrected] To determine risk factor profiles and cancer incidence rates among participants in the California Teachers Study (CTS), a study designed to document high breast cancer incidence rates of California teachers and to investigate emergent hypotheses in the etiology of breast and other cancers. METHODS: The CTS is a prospective study of 133,479 California female teachers and administrators, established in 1995-1996 with members of the California State Teachers Retirement System completing a detailed mailed questionnaire regarding possible risk factors for breast and other cancers. Cancer outcomes were identified by linkage with the California Cancer Registry. RESULTS: CTS participants have a 51% higher age-standardized invasive breast cancer incidence rate and a 67% higher in-situ breast cancer incidence rate than would be expected based on race-specific statewide rates after three years of follow-up. CTS participants also have substantially elevated rates of endometrial cancer (rate ratio, RR = 1.72), ovarian cancer (RR = 1.28), melanoma (RR = 1.59), non-Hodgkin's lymphoma (RR= 1.53), and leukemia (RR = 1.28), but low rates of invasive cervix cancer (RR = 0.53) and lung cancer (RR = 0.66). CONCLUSIONS: CTS members have high rates of several major cancers, particularly breast cancer, and low rates of lung and cervix cancer. Although late age at first birth can explain a portion of the observed excess risk of breast cancer in this cohort, the unique risk factor profile of CTS members may account for much of their higher risk of breast and selected other cancers. The CTS offers a rich resource for future studies of cancer risk and of women's health, in general.

Adult↗
PubMed2003

Alcohol use among adolescent mothers: heterogeneity in growth curves, predictors, and outcomes of alcohol use over time.

This paper examines patterns of alcohol use over a 10-year period in a sample of adolescent mothers and includes both predictors and outcomes of young mothers' alcohol use patterns over time. This study used mixture modeling to identify latent trajectory classes based on alcohol consumption over 10 years. Results indicate that there is significant heterogeneity in alcohol use trajectories of adolescent mothers during the transition from adolescence to adulthood as well as significant predictors and outcomes that vary by latent class trajectory. Specifically, measures of the consumption of alcohol by both quantity and frequency yielded multiple latent trajectory classes. Alcohol quantity measures yielded a two-class model with higher and lower quantity users. Age at first drink significantly differentiated between the two classes indicating that the younger the respondent was, the more likely she belonged to the higher quantity user class. In addition, members of the higher quantity class had significantly more negative outcomes in adulthood. The second measure of alcohol consumption, alcohol frequency, yielded a four-class solution consisting of low-level users, early decliners, late decliners, and increasers. As with alcohol quantity, age at first drink significantly differentiated between classes, as did age at first birth, in the expected direction. Similarly, two classes with the greatest growth and patterns of use over time, late decliners and increasers, had significantly worse outcomes in adulthood. The results suggest that identifying underlying heterogeneity in alcohol use can be informative with regard to both predictors and outcomes for young women who were adolescent mothers. Results suggest that there are possible higher order factors that can account for the results of this study.

Adolescent↗
PubMed2003

Familial breast cancer: scope for more susceptibility genes?

PURPOSE: The familial risk of female breast cancer is somewhat less than 2.0 when a first-degree relative is diagnosed with breast cancer, but it is not known to what extent heritable or environmental factors explain the familial clustering. Such data would be valuable for prevention and gene identification strategies. EXPERIMENTAL DESIGN: We used the nation-wide Swedish Family-Cancer Database on 10.2 million individuals and 190,000 mothers' and 26,000 daughters' breast cancers to calculate familial standardised incidence ratios (SIRs), for all invasive breast cancers in daughters, who were 0-66 years old. Over 5500 familial breast cancers were recorded. RESULTS: The familial SIR for all invasive breast cancer was 1.71 by breast cancer in the mother only, 1.95 by breast cancer in a sister only, and 2.75 by breast cancer in both a mother and sister. The SIRs did not change when adjustments were done for period, age at first birth, parity, socio-economic status and region. Age difference between sisters showed a small variation in risk for breast cancer but the highest SIR was found for those whose age difference was from 6 to 10 years. Half sisters showed an excess of familial risks exactly half of full sisters, the SIR being 1.44. CONCLUSIONS: These data suggest that familial aggregation of breast cancer is mainly due to heritable causes. Because the known susceptibility genes only explain about a quarter of the familial aggregation, the remaining majority offers a challenge to new genomic approaches.

Breast Neoplasms↗
PubMed2004

Hormonal factors and breast tumor proliferation: do factors that affect cancer risk also affect tumor growth?

BACKGROUND: Tumor cell proliferation is one of the most significant predictors of prognosis for women with breast cancer. Personal characteristics that affect hormonal exposure have been implicated in breast tumor etiology, and it is possible that they may also influence tumor cell proliferation. We examined the association between hormone-related breast cancer risk factors and breast tumor proliferation, as reflected in two proliferation measures, Ki-67 and mitotic count. METHODS: The study population was 484 women 40 years of age and older, who were members of a managed care organization's breast cancer screening program and were diagnosed with invasive breast cancer between 1988 and 1995. The percent of Ki-67 positive tumor cells averaged over four high powered fields (Ki-67) was log transformed and analyzed in a linear regression model. Mitotic count was dichotomized into high versus low (<or=10), and analyzed in an unconditional logistic regression model with the odds ratio (OR) as the measure of association. RESULTS: Consistent with other studies, there was a significant trend of decreased tumor cell proliferation with increasing age ( p for trend <0.05 for both measures). Higher body weight was associated with higher Ki-67 ( p for trend <0.05), but not with higher mitotic count. We found no significant associations between any reproductive factors (age at menarche, parity, age at first birth, menopausal status and age at menopause) and either measure of tumor cell proliferation. We observed an association between reduced tumor proliferation, as measured by mitotic count and former/current use of hormone replacement therapy (HRT) in comparison to never use (adjusted OR's: former HRT use: 0.40 (95% CI 0.19-0.85); current HRT use: 0.52 (95% CI 0.26-1.04). CONCLUSION: Certain factors related to hormonal exposure that influence breast tumor etiology, for example, age, also appear to increase tumor growth. Conversely HRT use, which clearly increases breast cancer risk, may not adversely affect, and possibly may diminish cell proliferation once tumors are established.

Adult↗
PubMed2003

Risk of melanoma in relation to smoking, alcohol intake, and other factors in a large occupational cohort.

OBJECTIVE: To investigate whether smoking, alcohol intake, female hormonal or anthropometric factors affect melanoma risk. METHODS: Using Cox proportional hazards regression analyses, we analyzed 68,588 white subjects (79% female) from the US Radiologic Technologists (USRT) Study who were cancer-free (other than non-melanoma skin cancer) as of the first of two self-administered questionnaires. Follow-up covered 698, 028 person-years, with 207 cases of melanoma. RESULTS: We found that melanoma risk was not associated with height, weight or BMI, nor with age at menarche, menopausal status, use of hormone replacement therapy, parity, age at first birth or oral contraceptive use. Melanoma risk was elevated with increasing alcohol use (RR: 2.1: 95% CI: 0.9-4.8, for > 14 drinks/week compared to never drinking; (p(trend) = 0.08)). Smoking for long durations compared to never smoking was inversely related to melanoma risk (RR: 0.6; 0.3-1.3; > or = 30 years; p(trend) = 0.03), though risk was not associated with number of packs smoked per day. CONCLUSIONS: None of the anthropometric or female reproductive/hormonal factors evaluated were related to melanoma risk. It is unclear whether the positive association with alcohol intake and inverse association with smoking for long duration are causal. The alcohol and smoking findings warrant detailed assessment in studies with substantial statistical power where potential biases can be more fully evaluated.

Adult↗
PubMed2001

Epidemiology of breast cancer: an environmental disease?

Breast cancer is the leading cancer site in women, both in the developed and the developing world. Incidence rates are increasing in many countries, although, in some, mortality may be stable or slightly decreasing. Geographical differences exist, with high rates of disease in North America, North Europe and Oceania, intermediate rates in South and Central America as well as South and East Europe, and low rates in Africa and Asia. Most of the literature reports that genetic inherited factors account for less than 5% of cases, although some authors advance higher figures, up to about 10%. Risk factors for breast cancer are related to the reproductive life of women: early menarche, nulliparity or late age at first birth, late menopause, diet and physical exercise, as well as hormonal factors, be they endogenous (high levels of free or not bound to SHBG estrogens) or exogenous (long-term use of oral contraceptives or menopausal hormone replacement). The present review does not aim to be exhaustive and fully comprehensive, or to present in detail domains currently well known and accepted by all. On the contrary, it modestly wishes to highlight potentially controversial conditions which could in the future be recognized as new risk factors.

Africa↗
PubMed1988

Information-seeking and maternal self-definition during the transition to motherhood.

The self-definitional processes accompanying the transition to motherhood were examined in this study. A cross-sectional sample of more than 600 women who were planning to get pregnant within 2 years, pregnant, or in the postpartum stage completed extensive questionnaires pertaining to their experiences of pregnancy and motherhood. On the basis of the assumption of the "self-socialization" perspective that individuals actively construct their identities in response to life transitions, our analyses focused on the role of information-seeking in the developing self-definitions of women becoming mothers. As predicted, (a) women actively sought information in anticipation of a first birth, (b) they used this information to construct identities incorporating motherhood, and (c) after the birth the determinants of their self-definitions shifted from indirect sources of information to direct experiences with child care. Hence, consistent with the self-socialization perspective, information-seeking did play an important role in the women's developing self-conceptions during this life transition. Mechanisms by which information gathered may alter self-conception are discussed.

Adolescent↗
PubMed2001

Sexual activity and contraceptive practices among teenagers in the United States, 1988 and 1995.

OBJECTIVES: This report presents national estimates of sexual experience, contraceptive use, and selected aspects of sexual behavior among never-married males and females aged 15-19 years in the United States. Data are presented for the years 1988 and 1995 according to age, race and Hispanic origin, progress in school, and other relevant characteristics. Tables present trends over time as well as comparisons between subgroups. METHODS: Descriptive tables of numbers and percents are presented and interpreted. Data for females are from the National Survey of Family Growth, and data for males are from the National Survey of Adolescent Males. RESULTS: About half of all never-married teenagers, about 17.5 million, had had sexual intercourse at least once in 1995. For male teenagers, this represents a decline since 1988, and for females, the proportion was stable across the two time points. The proportion of teen females who had sex before age 15 years increased. In 1995, 29 percent of females and 19 percent of males had unprotected recent sexual intercourse. About one-quarter of teens used no contraceptives during their first sexual intercourse. The condom remained the most popular method of contraception. Although teenagers' use of oral contraceptives dropped between 1988 and 1995, use of injectable and implant contraceptives began. Teenagers with more highly educated mothers, mothers who delayed their first birth beyond age 19 years, those from two-parent families, and those whose schooling was on schedule, were less likely to engage in sexual risk behaviors. These teenagers, along with those who were Protestant, also experienced the largest improvements across time in sexual risk behaviors.

Adolescent↗
PubMed1985

Reproductive factors, oral contraceptives and risk of malignant melanoma: Western Canada Melanoma Study.

A study of 361 female melanoma patients and age matched controls was conducted in the four western provinces of Canada. Analysis of reproductive factors showed a significant negative association between number of livebirths and risk of melanoma. The relationship persisted for superficial spreading melanomas after adjustment for host pigmentation factors, freckling, and educational status. An inverse association between bilateral oophorectomy and risk of superficial spreading melanoma was also seen. No association was found between risk of melanoma and age at first birth, age at menarche and age at natural menopause. No association was found between risk of superficial spreading or nodular melanoma and use of either oral contraceptives or menopausal oestrogens.

Adult↗