Complex germline rearrangement of BRCA1 associated with breast and ovarian cancer

Germline mutations in BRCA1 predispose to breast and ovarian cancer. Most germline BRCA1 mutations are small insertions, deletions, or single base pair (bp) substitutions. These mutation classes are rarely found as somatic mutations in BRCA1. On the other hand, somatic deletions of multiple mega-base pairs (Mb) including BRCA1, as reflected by loss of heterozygosity, occur frequently in both inherited and sporadic breast and ovarian cancers. To determine whether deletions or rearrangements of hundreds to thousands of bps might contribute to inherited mutation in BRCA1, we developed a Long PCR strategy for screening the entire genomic BRCA1 locus in high-risk families. We evaluated genomic DNA from one high-risk family of European ancestry with BRCA1-linked cancer in which no genomic mutations had been detected using conventional methods. Long PCR revealed a complex mutation, g.12977 ins10 del1039 (based on GenBank L78833), comprising an inverted duplication and deletion in BRCA1 that removes portions of exon 3 and intron 3, including the 5' splice site for intron 3. As a result of the deletion, exon 3 is skipped, leading to a truncated protein and disease predisposition. Unlike previously reported large germline deletions in BRCA1, neither breakpoint resides within an Alu element. The g.12977 ins10 del1039 mutation was not detected among 11 other breast cancer families, nor among 406 breast cancer patients unselected for family history.

A population-based case-control study of farming and breast cancer in North Carolina

We examined the role of farming and pesticide exposure among 862 cases and 790 controls in a population-based, case-control study of breast cancer conducted in North Carolina between 1993 and 1996. We obtained exposure information through personal interview. Increasing duration of farming was inversely associated with breast cancer risk; odds ratios (95% confidence intervals) were 1.2 (0.8-1.7), 0.8 (0.5-1.2), 0.7 (0.5-1.1), and 0.6 (0.4-0.9) for 1-10, 11-17, 18-23, and >23 years of farming, respectively, relative to nonfarmers. Inverse associations persisted when farming was restricted to calendar time periods of 2,2-bis(p-chlorophenyl)- 1,1,1-trichloroethane (DDT) use or to farming at ages 9-16. Among women who farmed, odds ratios (ORs) were elevated for those who reported being present in fields during or shortly after pesticide application (OR = 1.8, 95% CI = 1.1-2.8) and for those who reported not using protective clothing while applying pesticides (OR = 2.0; 95% CI = 1.0-4.3), but not among those who reported using protective clothing (OR = 0.8; 95% CI = 0.4-1.8). We conclude that residence or work on farms may be associated with a reduced risk of breast cancer. Nevertheless, our results suggest a possible increased risk of breast cancer among a subgroup of farming women who were most likely to be exposed to pesticides.

Heritability of factors of the insulin resistance syndrome in women twins

The insulin resistance syndrome (IRS) is characterized by a combination of interrelated coronary heart disease (CHD) risk factors, including low high-density lipoprotein cholesterol (HDL-C) levels, obesity and increases in triglyceride (TG), blood pressure, small low-density lipoprotein particles (LDL), and both fasting and postload plasma insulin and glucose. Using factor analysis, we previously identified 3 uncorrelated factors that explained 66% of the variance among these variables, based on data from women participating in examination 2 of the Kaiser Permanente Women Twins Study in Oakland, CA during 1989-1990. The factors were interpreted as: 1) body mass/fat distribution, 2) insulin/glucose, and 3) lipids: TG, HDL-C, LDL peak particle diameter. In this analysis, heritability of each of the factors was estimated based on data from 140 monozygotic and 96 dizygotic pairs of non-diabetic women twins. Heritability estimates were calculated using the classical approach, the analysis of variance (ANOVA) approach, and the maximum likelihood approach. For the body mass/fat distribution factor heritability estimates suggest moderate genetic influences; 0.61 (P < 0.001), 0.14 (P > 0.05), and 0.71 (P < 0.001), respectively. The insulin/glucose factor appeared to be highly heritable, with estimates of 0.87, 0.92, and 0.57 (all P < 0.001), respectively. The heritability estimates for the lipid factor were moderate and consistent across methods: 0.25 (P < 0.10), 0.32 (P < 0.05), and 0.30 (P < 0.05), respectively. These results are consistent with genetic influences on each of the 3 "factors," and suggest that both genetic and environmental effects are involved in the clustering of IRS risk factors.

Identifying genetic markers to assess the presence of gene-environment interactions

We analyzed a randomly chosen replicate with the goals of locating the closest markers to the genes involved in the discrete trait and utilizing these as surrogates for the genes in assessing the presence of gene-environment interactions. We screened the markers with an association test prior to using the transmission-disequilibrium test. We performed a segregation analysis, with regressive models and including the selected markers, to understand the underlying genetic mechanism and the role of the environmental factor. We were unsuccessful in locating the relevant markers due to the absence of linkage disequilibrium. Nevertheless, some insights were gained from the methods used.

Glutathione S-transferases M1, T1, and P1 and breast cancer

We examined associations for glutathione S-transferases M1 (GSTM1), T1 (GSTT1), and P1 (GSTP1) genotypes and breast cancer in the Carolina Breast Cancer Study, a population-based, case-control study in North Carolina. Odds ratios were close to the null value for each GST locus among African-American women (278 cases and 271 controls) and white women (410 cases and 392 controls), as well as pre- and postmenopausal women. For women with a history of breast cancer in one or more first-degree relatives, odds ratios were 2.1 (95% confidence interval, 1.0-4.2) for GSTM1 null and 1.9 (0.8-4.6) for GSTT1 null genotypes. Among women with a family history, age at diagnosis was significantly earlier for those with the GSTM1 null genotype. We did not observe strong evidence for modification of odds ratios for smoking according to GST genotypes. There was no evidence for combined effects of GSTM1, GSTT1, and GSTP1 genotypes, and there were no combined effects for GST genotypes and the catechol O-methyltransferase genotype. We conclude that GSTM1, GSTT1, and GSTP1 genotypes do not play a strong role in susceptibility to breast cancer. However, the role of GST genotypes in age at onset and risk of breast cancer among women with a family history merits further investigation.

Menopausal hormones and breast cancer in a biracial population

OBJECTIVES

This study examined the association between menopausal hormones and breast cancer in a biracial population.

METHODS

Logistic regression was used to calculate odds ratios for breast cancer associated with hormone use among 397 cases and 425 controls, all menopausal women.

RESULTS

Odds ratios for ever use of hormones were 0.8 (95% confidence interval [CI] = 0.5, 1.2) for White women and 0.7 (95% CI = 0.4, 1.2) for Black women. Risk was not increased with longer duration of use or more recent use.

CONCLUSIONS

Breast cancer risk was not increased among White or Black women who used menopausal hormones, despite patterns of use varying considerably between races.

Linkage of the cholesteryl ester transfer protein (CETP) gene to LDL particle size: use of a novel tetranucleotide repeat within the CETP promoter

BACKGROUND

A preponderance of small, dense LDL particles, elevated levels of plasma triglycerides (TG), and low levels of HDL characterize the atherogenic lipoprotein phenotype, which is associated with increased coronary artery disease (CAD) risk. Genetic and environmental factors influence LDL size, cholesteryl ester transfer protein (CETP) being one of the candidate genes. CETP mediates the transfer of cholesteryl ester from HDL to apolipoprotein (apo) B-containing lipoproteins in exchange for TG, promoting reverse cholesterol transfer and remodeling of lipoprotein particles.

METHODS AND RESULTS

We have identified a tetranucleotide repeat (fragment sizes from 324 to 464 bp; heterozygosity index = 0.74) within the CETP promoter and used it in quantitative sib-pair linkage analysis in 119 female dizygotic (DZ) twins. Linkage was found to LDL size (P<0.001), TG (P<0.005), and plasma apoB (P = 0.02). The distribution of the tetranucleotide repeats was bimodal, and there was strong allelic association of the "short" alleles with the B2 allele of CETP TaqIB polymorphic site (P<0.001).

CONCLUSIONS

This report of linkage of the CETP gene to LDL particle size adds to the list of candidate genes linked to LDL size, supporting the hypothesis of multigenic determination of LDL size heterogeneity. Whether this promoter variation is itself functional or is a marker for a functional site in the CETP gene remains to be determined.

Menstrual risk factors and early-onset breast cancer

OBJECTIVES

Epidemiologic studies provide evidence for increased breast cancer risk among women with prolonged exposure to endogenous estrogens and progesterone. Menstrual cycle characteristics, such as early menarche, rapid initiation of regular ovulatory cycles, short cycle length, and more days of flow, all potentially contribute to higher cumulative ovarian hormone exposure.

METHODS

We assessed the associations between these characteristics and breast cancer risk in a population-based, case-control study of 1505 controls and 1647 newly diagnosed cases, all younger than 45 years of age.

RESULTS

Compared to women with menarche at > or =15 years, we observed some increase in risk for women with younger ages at menarche, although those with very early ages were not at particularly high risk [odds ratio (OR) = 1.5, 95% confidence interval (CI) = 1.1-1.9 for menarche at age 12 and OR = 1.2, 95% CI = 0.9-1.7 for menarche at age < or =10]. Women who reported having regular menstrual cycles within 2 years of menarche were at increased breast cancer risk (OR = 1.7, 95% CI = 1.2-2.3), compared to those never having regular cycles. Stratification by current body mass index revealed slightly stronger associations with menstrual characteristics among thinner women (< 22.0 kg/m2) compared to heavier women (> 28.8 kg/m2).

CONCLUSIONS

These findings suggest that future studies should focus on clarifying how the interrelated effects of body size and menstrual factors, such as age at menarche and cycle regularity, contribute to breast cancer etiology.

Body size and breast cancer risk in black women and white women: the Carolina Breast Cancer Study

The relation between body size and breast cancer risk was investigated in a population-based, case-control study of Black women (350 cases, 353 controls) and White women (523 cases, 471 controls) from North Carolina, aged 20-74 years in 1993-1996. Logistic regression analyses compared tertiles of each body size variable, adjusting for age and breast cancer risk factors (results shown for highest relative to lowest tertile). Among premenopausal women, body mass index (kg/m2) was inversely associated with breast cancer (odds ratio (OR) = 0.46, 95% confidence interval (CI): 0.26, 0.80) for Whites but not for Blacks. There was essentially no association among postmenopausal women. Higher waist/hip ratio, adjusted for body mass index, increased risk for all women. Odds ratios for Black and White premenopausal women were 2.50 (95% CI: 1.10, 5.67) and 2.44 (95% CI: 1.17, 5.09), respectively; odds ratios for Black and White postmenopausal women were 1.62 (95% CI: 0.70, 3.79) and 1.64 (95% CI: 0.88, 3.07), respectively. Findings for body mass index differed among Black women when stratified by age (<50 years) (OR = 0.50, 95% CI: 0.25, 1.01) instead of menopausal status. Thus, the associations of breast cancer with body mass index and waist/hip ratio among Black women are similar to those documented for Whites, despite different body size profiles on average.

Alcohol consumption and breast cancer among black and white women in North Carolina (United States)

OBJECTIVE

The purpose of this study was to investigate the effects of alcohol consumption on breast cancer risk in black and white women.

METHODS

We used data from the Carolina Breast Cancer Study, a population-based, case-control study of black and white women in North Carolina. Interviews were conducted with 890 cases and 841 controls frequency-matched on age and race.

RESULTS

Overall, the prevalence of moderate to high levels of alcohol consumption was low. Compared with abstainers, the multivariate odds ratio for recent intake of one or two drinks per day was 1.4 (95% CI = 0.9-2.1) and two or more drinks a day was 1.0 (95% CI = 0.6-1.6); increasing consumption was not associated with risk (p for trend = 0.6). The associations were similar, but somewhat weaker, for average lifetime consumption. Among women who consumed 91 g/week or more of alcohol, a nonsignificant increased risk of breast cancer was observed for women reporting binge drinking (OR = 1.5; 95% CI = 0.9-2.3), but not for those who consumed less than 91 g/week reporting binge drinking (OR = 1.0; 95% CI = 0.6-1.5). Odds ratios did not differ meaningfully by race, age, menopausal status, exogenous hormone use, or body mass index.

CONCLUSIONS

These data provide little evidence for an association between alcohol consumption and risk of breast cancer among either black or white women.

Hormone-related factors and risk of breast cancer in relation to estrogen receptor and progesterone receptor status

Risk factors were examined for subgroups of breast cancer characterized by estrogen receptor (ER) and progesterone receptor (PR) status. Data from the Carolina Breast Cancer Study, a population-based, North Carolina case-control study of 862 breast cancer cases aged 20-74 years diagnosed during 1993-1996 and 790 controls frequency matched on race and age, were obtained by personal interview. ER and PR status was retrieved from medical records (80%) or was determined in the authors' laboratory (11%) but was missing for 9% of cases. The receptor status distribution was as follows: 53% ER+PR+, 11% ER+PR-, 8% ER-PR+, and 28% ER-PR-. Several hormone-related factors were associated with stronger increased risks for ER+PR+ than for ER-PR- breast cancer: the elevated odds ratios were strongest for ER+PR+ breast cancer among postmenopausal women who had an early age at menarche (odds ratio (OR) = 1.6, 95% confidence interval (CI): 1.0, 2.4), nulliparity/late age at first full-term pregnancy (OR = 1.7, 95% CI: 0.9, 3.2 and OR = 1.6, 95% CI: 1.0, 2.7, respectively), or a high body mass index (OR = 1.6, 95% CI: 0.9, 3.0) and among pre-/perimenopausal women who had a high waist-hip ratio (OR = 1.9, 95% CI: 1.2, 3.1). In contrast, family history of breast or ovarian cancer and medical radiation exposure to the chest produced higher odds ratios for ER-PR- than for ER+PR+ breast cancer, especially among pre-/perimenopausal women.

The associations of adolescent cigarette smoking, alcoholic beverage consumption, environmental tobacco smoke, and ionizing radiation with subsequent breast cancer risk (United States)

OBJECTIVES

Studies of breast cancer among survivors of the World War II atomic bomb blasts over Japan suggest that the adolescent breast may be particularly sensitive to carcinogenic insult. To further explore that possibility we examined the relationships of cigarette smoking, alcohol consumption, environmental tobacco smoke (ETS) exposure, and medical treatment with ionizing radiation during adolescence with subsequent breast cancer risk.

METHODS

Data from the Carolina Breast Cancer Study, a population-based, case-control study of breast cancer in North Carolina women aged 20-74 years (864 cases, 790 controls), were analyzed.

RESULTS

A modest increase in breast cancer risk was suggested for women who began to smoke cigarettes between the ages of 10 and 14 years (OR: 1.5, CI: 0.9-2.5), and for women exposed to ionizing radiation between ages 10 and 19 years to treat or monitor a medical condition (OR: 1.6, CI: 0.5-2.5). Neither exposure to ETS at home prior to age 18 years (OR: 1.1, CI: 0.9-1.3) nor initiation of alcoholic beverage consumption between ages 10 and 15 years (OR: 1.1, CI: 0.6-1.8) appeared to increase risk.

CONCLUSIONS

Our results are consistent with previous evidence suggesting that some adolescent exposures could influence future breast cancer risk.

Genetic polymorphisms in uridine diphospho-glucuronosyltransferase 1A1 and association with breast cancer among African Americans

We examined the role of constitutional genetic variation at the UDP-glucuronosyltransferase (UGT) 1A1 locus in breast cancer susceptibility. The UGT1A1 enzyme is a major UGT involved in estradiol glucuronidation. To date, four UGT1A1 variant alleles characterized by a variation in the number of TA from five through eight repeats in the atypical TATA box region have been described in the African-American population. Functional analyses of the transcriptional activity in breast and liver cells revealed that the transcription activation of a reporter gene is inversely correlated with the number of repeats. Reverse transcription-PCR analysis confirmed the expression of UGT1A1 in human liver in the hepatocarcinoma cell line HepG2 and provided evidence of the expression of UGT1A1 in breast cancer tissue, where a positive signal was observed in 11 of 12 breast cancer cell lines tested. The population-based case-control study involved 200 women with breast cancer and 200 female controls of African ancestry. We postulated that breast cancer cases might have a higher prevalence of low activity allele-containing genotypes than controls (alleles presenting seven and eight repeats in the A(TA)nTAA motif of the TATA box). The age-adjusted odds ratio (OR) for breast cancer comparing women with seven and eight allele-containing genotypes versus 5/5, 5/6, and 6/6 genotypes was 1.8 [95% confidence interval (CI), 1.0-3.1; P = 0.06] in premenopausal women and 1.0 (95% CI, 0.5-1.7; P = 0.9) in postmenopausal women. The observed 1.8-fold elevated risk in premenopausal women with invasive breast cancer is highly suggestive of a possible interaction between UGT genotype and hormones. Additional analyses suggested a stronger association of UGT1A1 genotype with estrogen receptor (ER)-negative breast cancer. Among premenopausal women, the association was stronger for ER- breast cancer (OR, 2.1; 95% CI, 1.0-4.2; P = 0.04) than ER+ breast cancer (OR, 1.3; 95% CI, 0.6-3.0; P = 0.5). The OR was slightly stronger among women who used oral contraceptives, and the association remained null in postmenopausal women, regardless of whether they took hormone replacement therapy. Our current findings suggest that further investigations are warranted to elucidate the role of UGT1A1 in breast cancer risk.

Risk of breast cancer according to the status of HER-2/neu oncogene amplification

We examined risk factors for breast cancer after subdividing cases based on the presence of HER-2/neu oncogene amplification in their tumors. Data were from the Carolina Breast Cancer Study, a population-based, case-control study of 577 invasive breast cancer patients, diagnosed during 1993-1996 and ages 20-74 years, and 790 controls frequency-matched on race and age. Information on breast cancer risk factors was obtained from structured personal interviews. About 20% of paraffin-embedded tissues from the breast cancers of cases were identified as positive for HER-2/neu amplification (HER-2/neu+) by differential PCR. Early age at menarche, higher waist:hip ratio, and family history of breast or ovarian cancer were associated with elevated odds ratios (ORs) for both HER-2/neu+ and HER-2/neu- breast cancers. Breastfeeding for at least 1 year was inversely associated with HER-2/neu+ breast cancer [OR, 0.3; 95% confidence interval (CI), 0.1-0.7] more so than HER-2/neu- breast cancer (OR, 0.8; 95% CI, 0.5-1.2). Most of the remaining risk factors had ORs around 1.0 for both HER-2/neu+ and HER-2/neu- breast cancers, although a few exhibited possible associations with one disease subtype in analyses stratified by menopausal status. These study results suggest that most recognized breast cancer risk factors do not operate through HER-2/neu amplification in breast carcinogenesis. Differential effects of long-term breastfeeding by HER-2/neu amplification status have been observed in earlier studies and are provocative; however, the direction and magnitude of the associations have not been consistent.

Exploring the role of environmental factors in association and linkage studies

We analyzed some simulated data to assess the success of statistical methodologies to establish the role of the environmental factors (EF) and to identify associated and linked markers. We considered five replicates for each of the four studies, and, with the knowledge of the generating model, concentrated our analyses on chromosomes (CH) 1, 3, and 5. To determine the influence of EF and associated markers on the affection status (AS), we utilized chi-square tests for independence and recursive partitioning (via the CART software). To identify linked markers, we scanned the relevant chromosomes with nonparametric multipoint linkage (NPL) and transmission/disequilibrium tests. These analyses were performed on the whole data set as well as on subsets of individuals and families defined by exposure to EF. CART correctly selected the associated marker (D1G024) and EF1 for Study (ST) 1 and did not generate trees for the other studies. NPL identified the relevant regions on CH3 and CH5 but failed to do so for CH1, except in ST4. Stratifying families by exposure to EF1 did not consistently increase sensitivity of NPL to the relevant CH3 markers, but did help characterize the genetic heterogeneity and identify linked families.

Policy guidelines for the utilization of formalin-fixed, paraffin-embedded tissue sections: the UNC SPORE experience. University of North Carolina Specialized Program of Research Excellence

Paraffin blocks represent a valuable resource that has allowed investigators to apply today's technology to address scientific questions in a shorter period of time and in more diverse populations than would have been possible with fresh or frozen tissue. However, in addition to being an exhaustible resource, there is concern regarding the appropriate use of these tissues, both with respect to medical or legal considerations and quality control and quality assurance practices. We describe policy guidelines to address these concerns, including: safeguards to address medical/legal and patient confidentiality issues, quality control and quality assurance for tissue sectioning, processing and storage, database management for sample tracking, and scientific review for utilization of specimens. These policies and procedures have been developed and implemented by the University of North Carolina (UNC) Specialized Program of Research Excellence (SPORE) in the Breast Cancer Immunohistochemistry (IHC) Core laboratory, in collaboration with our study pathologists, participants, and research investigators. It is our hope that the information and experience described here may stimulate discussion that can ultimately lead to a uniform policy for handling formalin-fixed paraffin-embedded tissues in research.

Single nucleotide polymorphisms (SNPs) in the estrogen receptor gene and breast cancer susceptibility

In order to evaluate the role of inherited variation in the estrogen receptor (ESR1) gene in human breast cancer, we determined intronic sequences flanking each ESRI exon; identified multiple SNPs and length polymorphisms in the ESR1 coding sequence, splice junctions and regulatory regions; and genotyped families at high risk of breast cancer and population-based breast cancer patients and controls. Of 10 polymorphic sites in ESR1, four are synonymous SNPs, two are nonsynonymous SNPs and four are length polymorphisms; five are novel. No ESR1 polymorphisms were associated with breast cancer, either in the high-risk families or the case-control study. We therefore conclude that inherited genetic variation is not a mechanism by which the estrogen receptor is commonly involved in breast cancer development.

Imaging of medical disease of the newborn lung

Surfactant deficiency remains the most common and serious pulmonary affliction of premature infants. Exogenous surfactant and corticosteroid administration have had a major impact in improving survival and morbidity in this disease with consequent alterations in the clinical and radiographic course. Chronic lung disease, although still common, is usually less severe than previously, especially in larger infants. Significant therapeutic strides in treating persistent pulmonary hypertension with or without meconium aspiration have been the use of high-frequency ventilators, inhaled nitric oxide, and ECMO. Prompt recognition and treatment of infection, atelectasis, and air leak whether primary or secondary are important to overall outcome. Less common pulmonary conditions, such as lymphangiectasia, pulmonary hypoplasia, and alveolar proteinosis, may initially masquerade as more common lesions. Persistent pulmonary hypertension is often the initial diagnosis and part of the clinical problem. Attention must be paid to the clinical and radiographic appearance and excursion of the thoracic cage because deformities and malformations may be the cause of respiratory problems.

A simple method to enrich an Agrobacterium-transformed population for plants containing only T-DNA sequences

A simple modification to standard binary vector design has been utilized to enrich an Agrobacterium-transformed population for plants containing only T-DNA sequences. A lethal gene was incorporated into the non-T-DNA portion of a binary vector, along with a screenable marker. The resulting class of vectors is designated as NTL T-DNA vectors (non-T-DNA lethal gene-containing T-DNA vectors). The lethal gene used here is a CaMV 35S-barnase gene with an intron in the coding sequence (barnase-INT); the screenable marker is a pMAS-luciferase gene with an intron in the coding sequence (LUC-int). To evaluate the utility of this vector design, tobacco plants were transformed with either the NTL T-DNA vector or a control vector from which most of the barnase-INT gene was deleted. Populations of 50 transgenic plants were scored for LUC expression. The results indicated a dramatic reduction in the presence of non-T-DNA sequences in the transgenic population using the NTL T-DNA vector. Only one transgenic plant was found to be LUC+ using the NTL vector, compared with 42 of 50 plants using the control vector. Importantly, the efficiency with which transformed tobacco plants was obtained was reduced by no more than 30%. The reduction in LUC+ transgenics was partially reversed when a barstar-expressing tobacco line was transformed, indicating that barnase expression was responsible for the reduced frequency of incorporating non-T-DNA sequences. Similar transformation results were obtained with tomato and grape. The incorporation of a barnase-INT gene outside the left border appears to provide a generally applicable tool for enriching an Agrobacterium-transformed population for plants containing only T-DNA sequences.

The association between extent of employment and hypertension among women participants of the Second National Health and Nutrition Survey

The association between extent of employment and hypertension was examined among 3,824 women participants of the Second National Health and Nutrition Examination Survey. Women in three employment groups (full-time, part-time, and short-term) were compared to homemakers. In covariate-adjusted, logistic regression models, women employed full-time had a somewhat lower, but not significantly different, prevalence of hypertension (OR = 0.8, 95% CI = 0.7, 1.1), whereas both part-time (OR = 0.6, 95% CI = 0.4, 0.7) and short-term (OR = 0.5, 95% CI = 0.4, 0.7) workers had significantly lower prevalences. Associations did not tend to vary by age, ethnicity, or occupation. Employment does not appear to increase the risk of hypertension in women; in fact, moderate levels were associated with lower risk.

Physical activity at age 12 and adult breast cancer risk (United States)

OBJECTIVES

Some epidemiologic studies suggest that adolescent physical activity reduces subsequent breast cancer risk. To examine this question further, we analyzed data on physical activity at age 12 that had been collected as part of the Carolina Breast Cancer Study (CBCS).

METHODS

The CBCS is a population-based, case-control study of 527 white and 337 African-American cases and 790 controls, frequency-matched on age and race. Respondents were asked whether, and to what extent, they engaged in four specific activities at age 12 (walking to school, biking to school, competitive training, performing vigorous household chores).

RESULTS

Women who reported participation in any of the four activities had a modest reduction in breast cancer risk (odds ratio (OR): 0.8, 95% confidence interval (CI): 0.6-1.0). Using an index measuring approximate number of activity episodes per week, analyses revealed modest inverse relationships for nearly all levels of activity relative to no reported activity; a weighting of the index by metabolic equivalent scores produced similar results.

CONCLUSIONS

Our findings support the hypothesis that adolescent physical activity may protect against adult breast cancer, even at moderate levels.

Adolescent reproductive events and subsequent breast cancer risk

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.

Women, employment status, and hypertension: cross-sectional and prospective findings from the Atherosclerosis Risk in Communities (ARIC) Study

PURPOSE

This study examined the cross-sectional and prospective associations between employment status and hypertension among middle-aged, African-American (AA) and European-American (EA) women participating in the Atherosclerosis Risk in Communities Study.

METHODS

Employed women and homemakers from the baseline examination (1987-89) were included in the cross-sectional study (n = 7351). Associations between employment and the incidence of hypertension ascertained at visit 2 (1990-92) were determined among those who at baseline, had low-normal blood pressure (not hypertensive and systolic blood pressure (SBP) < or = 120 mm Hg systolic and diastolic blood pressure (DBP) < or =80 mm Hg (n = 3194). Logistic regression analysis was used to examine the association between employment status and hypertension by ethnicity, taking into account covariates.

RESULTS

At baseline, employed women were less likely to be hypertensive (SBP > or =140 mm Hg or DBP > or =90 mm Hg or current use of antihypertensive drugs) than were homemakers (prevalence odds ratio) (POR) = 0.70; 95% confidence interval (CI) = 0.62-0.79), controlling for age, body mass index, and education. Among the subgroup who had low-normal blood pressure at baseline, employed women were less likely to develop hypertension during the three-year time period than were homemakers (odds ratio (OR) = 0.68; 95% CI = 0.44-1.05). The inverse association was stronger among AA (RR = 0.37; 95% CI = 0.16-0.88) than EA (OR = 0.83; 95% CI = 0.50-1.38) women.

CONCLUSIONS

These findings suggest that the inverse association between hypertension and employment status is not due to a healthy worker effect, and that employment may confer protection against incident hypertension in women.