Lactation and breast cancer risk: a case-control study in Connecticut

In this report, we examined the relationship between lactation and breast cancer risk, in a case-control study of breast cancer, conducted in Connecticut between 1994 and 1998. Included were 608 incident breast cancer cases and 609 age frequency matched controls, aged 30-80 years old. Cases and controls were interviewed by trained study interviewers, using a standardized, structured questionnaire, to obtain information on lactation and other major risk factors. Parous women who reported ever lactation had a borderline significantly reduced risk of breast cancer (OR = 0.83, 95% CI, 0.63-1.09). An OR of 0.53 (95% CI, 0.27-1.04) was observed in those having breastfed more than 3 children compared to those who never lactated. Women having breastfed their first child for more than 13 months had an OR of 0.47 (95% CI, 0.23-0.94) compared to those who never breastfed. Lifetime duration of lactation also showed a risk reduction while none of the ORs were statistically significant. Further stratification by menopausal status showed a risk reduction related to lactation for both pre- and postmenopausal women, while the relationship is less consistent for the latter. These results support an inverse association between breastfeeding and breast cancer risk.     

Interaction of dense breast patterns with other breast cancer risk factors in a case-control study

The question of interactions between breast density and other breast cancer risk factors is of interest, since it bears upon the use of density as a marker for changes in breast cancer risk. We studied breast parenchymal patterns and 13 other potential risk factors for breast cancer in 172 breast cancer cases and 338 age-matched controls in Singapore. Dense breast patterns were defined as having Tabar parenchymal pattern IV or V. We found significant interactions between dense patterns and ethnic group (P=0.046), and between dense patterns and number of deliveries (P=0.04). Among women with nondense breast patterns, the non-Chinese had lower risk than the Chinese with an odds ratio (OR) of 0.47 (95% CI 0.24, 0.88), whereas in those with dense patterns, the non-Chinese had considerably higher risks (OR=5.34, 95% CI 0.54, 52.51). Alternatively expressed, the increased risk with dense patterns was only observed in the non-Chinese (OR=13.99, 95% CI 1.33, 146.99). Among parous women, the protective effect of three or more deliveries was only observed in those with dense breast patterns (OR=0.21, 95% CI 0.06, 0.70). Suggestive but nonsignificant interactions with dense patterns were observed for ever having delivered, age at first delivery, breast feeding and body mass index. The results are consistent with dense breast patterns as a marker for hormonal modification of breast cancer risk.     

Diet and ovarian cancer risk: a case-control study in China

This case-control study, conducted in Zhejiang, China during 1999-2000, investigated whether dietary factors have an aetiological association with ovarian cancer. Cases were 254 patients with histologically confirmed epithelial ovary cancer. The 652 controls comprised 340 hospital visitors, 261 non-neoplasm hospital outpatients without long-term diet modifications and 51 women recruited from the community. A validated food frequency questionnaire was used to measure the habitual diet of cases and controls. The risks of ovarian cancer for the dietary factors were assessed by adjusted odds ratios based on multivariate logistic regression analysis, accounting for potential confounding demographic, lifestyle, familial factors and hormonal status, family ovarian cancer history and total energy intake. The ovarian cancer risk declined with increasing consumption of vegetables and fruits but vice versa with high intakes of animal fat and salted vegetables. The adjusted upper quartile odds ratio compared to the lower quartile was 0.24 (0.1-0.5) for vegetables, 0.36 (0.2-0.7) for fruits, 4.6 (2.2-9.3) for animal fat and 3.4 (2.0-5.8) for preserved (salted) vegetables with significant dose-response relationship. The risk of ovarian cancer also appeared to increase for those women preferring fat, fried, cured and smoked food.     

Case-control study of risk factors for breast cancer in Nigerian women

This study evaluated the potential risk factors for breast cancer in Nigerian women using a case-control design of 250 women with breast cancer and their age-matched female controls. Both cases and controls were recruited from 4 University Teaching Hospitals in Midwestern and Southeastern Nigeria. Data on the clinical and epidemiological characteristics were collected using interviewer-administered structured questionnaires. The mean age of the cases and controls were 46.1 and 47.1 years, respectively. Fifty-seven percent of the cases were premenopausal while 43% were postmenopausal. The association of risk factors with breast cancer was assessed using conditional logistic regression. Positive family history of breast cancer in first- and second-degree relatives (Odds ratio [OR] = 8.07, 95% confidence interval [CI], 1.003, 64.95, p = 0.04), education of high school level and above (OR = 1.35, 95% CI 1.04, 1.74, p = 0.0205), age at first fullterm pregnancy (FFTP) greater than 20 years (OR = 1.32 95% CI 1.01, 1.71, p = 0.0413) and waist/hip ratio (WHR) (OR = 1.98, 95% CI 1.27, 3.10, p = 0.0026) were associated with increased risk of breast cancer in the final multiple conditional logistic regression model. The findings from this study have shown that sociodemographic characteristics, reproductive variables and anthropometric measures are significant predictors of breast cancer risk in Nigerian women.     

Risk factors for breast cancer among women in Bhopal urban agglomerate: a case-control study

Background: Breast cancer is the most common cancer in females worldwide, and the second leading cause of cancer deaths in women. The incidence is on the rise in India, and breast cancer is the second most common malignancy in Indian women. Objective: To assess the risk factors for breast cancer patients living in Bhopal. Study Design and Method: This case-control study was conducted in Bhopal urban agglomerate for a period of a year from October 2008 to August 2009. Demographic data and reproductive risk factor related information was collected using a structured questionnaire with analyses by Epi-info and SPSS 16. Results: A history of oral contraceptive pill use (OR=2.77, 95% CI: 1.15-6.65), history of not having breastfeeding (OR=3.49, 95% CI:1.22-9.97), over weight (OR=0.11, 95%CI:0.02-0.49), obese women ( OR=0.24, 95%CI: 0.06-0.88) and family history of breast cancer (OR=3.89, 95% CI: 1.01-14.92) were associated significantly with the occurrence of breast cancer on multivariate analysis. Conclusions: The findings of the present study suggests that positive family history of breast cancer and history of using OCP may be the epigenetic factors promoting the occurrence of breast cancer while breastfeeding reduces the possibility of acquiring breast cancer.     

Dietary and other risk factors in women having fibrocystic breast conditions with and without concurrent breast cancer: a nested case-control study in Shanghai, China

Risk of breast cancer is increased in women with proliferative benign breast conditions. Most of these conditions, however, do not progress to breast cancer. The purpose of our study was to identify factors possibly associated with this progression. Women with proliferative fibrocystic breast conditions alone (214), and women with proliferative fibrocystic breast conditions and concurrent breast cancer (130), were compared to each other, and each of these groups of women were also compared to 1,070 controls; and 176 women with non-proliferative benign breast conditions alone, and 155 also with breast cancer, were similarly compared. All study subjects were selected from a cohort of women enrolled in a trial of breast self-examination in Shanghai. Women were interviewed to ascertain information on suspected risk factors for breast cancer and dietary habits. Conditional logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI). Increased risks of both proliferative fibrocystic breast conditions alone, and with breast cancer, were associated with low parity, a prior benign breast lump and breast cancer in a first-degree relative. Decreasing trends in the risk of both conditions with increasing intake of fruits and vegetables were observed. No factors were significantly associated with risk of breast cancer relative to risk of proliferative changes. Similar, but in some instances weaker, associations were observed for non-proliferative fibrocystic conditions with and without breast cancer. The possible risk or protective factors that were observed in our study most likely alter the risk of breast cancer at an early stage in the carcinogenic process, and probably do not alter risk of progression from proliferative fibrocystic breast conditions to breast cancer.     

Anthropometric factors and risk of molecular breast cancer subtypes among postmenopausal Norwegian women

Adult height and body weight are positively associated with breast cancer risk after menopause, but few studies have investigated these factors according to molecular breast cancer subtype. A total of 18,562 postmenopausal Norwegian women who were born between 1886 and 1928 were followed up for breast cancer incidence from the time (between 1963 and 1975) height and weight were measured until 2008. Immunohistochemical and in situ hybridization techniques were used to subtype 734 incident breast cancer cases into Luminal A, Luminal B [human epidermal growth factor receptor 2 (HER2?)], Luminal B (HER2+), HER2 subtype, basal‐like phenotype (BP) and five‐negative phenotype (5NP). We used Cox regression analysis to assess adult height and body mass index (BMI) in relation to risk of these subtypes. We found a positive association of height with risk of Luminal A breast cancer (p_trend, 0.004), but there was no clear association of height with any other subtype. BMI was positively associated with risk of all luminal breast cancer subtypes, including Luminal A (p_trend, 0.002), Luminal B (HER2?) (p_trend, 0.02), Luminal B (HER2+) (p_trend, 0.06), and also for the HER2 subtype (p_trend, 0.04), but BMI was not associated with risk of the BP or 5NP subtypes. Nonetheless, statistical tests for heterogeneity did not provide evidence that associations of height and BMI differed across breast cancer subtypes. This study of breast cancer risk among postmenopausal women suggests that height is positively associated with risk of Luminal A breast cancer. BMI is positively associated with risk of all luminal subtypes and for the HER2 subtype.     

Risk factors for premenopausal breast cancer: a case-control study in Uruguay

In order to thoroughly analyze risk factors of breast cancer (BC) in premenopausal Uruguayan women, a case-control study was carried out at the Pereira Rossell Women's Hospital, Montevideo, where 253 incident BC cases and 497 frequency-matched healthy controls were interviewed on menstrual and reproductive story, were administered a short food frequency questionnaire and undertook a series of body measurements necessary to calculate body composition and somatotype. Odds ratio (OR) coefficients were taken as estimates of relative risk derived from unconditional logistic regression. Among the classical risk factors, only the family history of BC in first degree relatives was significantly associated with risk of premenopausal BC (OR=2.20, 95% CI 1.33-3.62). Interestingly, this risk factor was found to be stronger in women of ages >40 (OR=4.05, 95% CI 2.10-7.81), late menarche (OR= 2.39, 95% CI 1.18-4.85), early age for their first delivery (OR=3.02, 95% CI 1.26-7.22), short time between menarche and first delivery (OR=3.22, 95% CI 1.29-8.07), and with high parity (OR=4.10, 95% CI 1.79-9.36), although heterogeneity was detected only for age and parity. High consumption of red meat was positively associated with the disease risk (OR=2.20, 95% CI 1.35-3.60), in the same way as fried foods (OR=1.79, 95% CI 1.12-2.84). Conversely, a high intake of plant foods displayed a protective effect (OR=0.41, 95% CI 0.26-0.65). Except for hypertension (OR=1.55, 95% CI 1.03-2.35), none of the analyzed components of metabolic syndrome were associated to BC risk. Particular increases of risk for premenopausal BC were found for family history in first degree relatives in certain subsets derived from the menstrual-reproductive history. Preventive strategies could broaden their scope if new studies confirm the present results, in view of the limited prevention measures that premenopausal BC currently has.     

Risk factors for breast cancer among Filipino women in Manila

Age‐adjusted incidence rates of breast cancer vary greatly worldwide with highest rates found in the typically ‘westernised’ countries of North America and Europe. Much lower rates are observed in Asian and African populations but an exception to this has been reported for the Manila Cancer Registry in the Philippines. The reason for this high rate is unknown but may be associated with the change in lifestyle that has occurred in urban Manila since the 1960s. In 1995, a randomised controlled trial was set up in Manila to evaluate the feasibility of a screening intervention by clinical breast examination as an alternative to mammography. The cohort of 151,168 women was followed‐up to 2001 for cancer incidence and a nested case‐control study carried out. This aimed to evaluate the increase in breast cancer risk associated with known risk factors. Increased risks were seen for a high level of education (OR = 1.9 95%CI 1.1–3.3 for education stopped at ≥13 versus <13 years), nulliparity (OR = 5.0 95% CI 2.5–10.0 for nulliparity versus five or more children), and late age at first birth (OR = 3.3 95% CI 1.3–8.3 for age ≥30 versus <20 years). We found no association with excess body weight, height, use of exogenous hormones or alcohol consumption. From this study, the recognised “classical” risk factors do not fully explain the high breast cancer incidence in Metro Manila, especially when compared to other urban Asian populations. We conclude that it is too simplistic to ascribe the high risk to ‘westernisation’.     

Behavioral risk factors among Black and White women newly diagnosed with breast cancer

BACKGROUND: To determine the rates of three behavioral risk factors (depression symptoms, smoking, and drinking) among women newly diagnosed with breast cancer and to examine if the rates under investigation differed between Black and White women. METHOD: Subjects were 147 women (47% Black, 53% White) newly diagnosed with breast cancer and participating in an epidemiologic interview study conducted at two metropolitan area cancer centers in the same city. The epidemiologic interview included women's tobacco, alcohol, and drug use history, medical and family history, and depression symptoms. RESULTS: Among all women in the sample, 33% reported clinically significant depression symptoms, 10% currently smoked cigarettes, and 57% currently drank alcohol. Seventy percent of women reported experiencing one or more behavioral risk factors, and White women were more likely than Black women to do so. After controlling for other demographic variables, White women were 50% more likely to report clinical symptoms of depression (odds ratio=1.55, 95% confidence interval=1.03, 2.30) and over two times more likely to report being current drinkers (odds ratio=2.19, 95% confidence interval=1.45, 3.30) than were Black women (p<0.05). CONCLUSIONS: The results suggest that certain behaviors of Black women may be associated with lower levels of self-reported distress. These findings also suggest the need for further research to examine behavioral comorbidity among women with breast cancer, and the roles that race, ethnicity, and culture may play in their expression.     

Cytomegalovirus, Epstein-Barr virus and risk of breast cancer before age 40 years: a case-control study

We investigated whether there is an association between cytomegalovirus (CMV) and Epstein-Barr virus (EBV) IgG levels and risk of breast cancer before age 40 years. CMV and EBV IgG levels were measured in stored plasma from 208 women with breast cancer and 169 controls who participated in the Australian Breast Cancer Family Study (ABCFS), a population-based case-control study. CMV and EBV IgG values were measured in units of optical density (OD). Cases and controls did not differ in seropositivity for CMV (59 and 57% respectively; P=0.8) or EBV (97 and 96% respectively; P=0.7). In seropositive women, mean IgG values were higher in cases than controls for CMV (1.20 vs 0.98 OD, P=0.005) but not for EBV (2.65 vs 2.57 OD, P=0.5). The adjusted odds ratios per OD unit were 1.46 (95% CI 1.06-2.03) for CMV IgG and 1.11 (0.93-1.33) for EBV IgG. The higher mean CMV IgG levels found in women with breast cancer could be the result of a more recent infection with CMV, and may mean that late exposure to CMV is a risk factor for breast cancer.     

Lifelong vegetarianism and risk of breast cancer: a population-based case-control study among South Asian migrant women living in England

To investigate the role of lifelong vegetarianism on the aetiology of female breast cancer, we conducted a population-based case-control study among South Asian migrant women from the Indian subcontinent resident in England. A total of 240 South Asian breast cancer cases were identified from 2 cancer registries during 1995-1999. For each case, 2 age-matched South Asian controls were randomly selected from the age-sex register of the case practice. Lifelong vegetarians had a slight reduction, although not statistically significant, in the odds of breast cancer relative to lifelong meat-eaters, which persisted after adjustment for socio-demographic and reproductive variables [odds ratio (OR)=0.77; 95% confidence interval (CI)=0.50-1.18]. Analysis by food group revealed no linear trend in the odds of breast cancer with increasing consumption of meat (p=0.10) but the odds were higher for women in the top 75%. In contrast, there were strong inverse trends in the odds of breast cancer with increasing intake of vegetables (p=0.005), pulses (p=0.007) and fibre [non-starch polysaccharides, NSP (p=0.02)], with women in the highest 25% of intake of these foods having about 50% of the odds of those in the lowest ones. Adjustment for intake of vegetables and pulses reverted the odds of breast cancer in lifelong vegetarians relative to lifelong meat-eaters (OR=1.04; 95% CI=0.65-1.68) and attenuated the quartile-specific estimates for meat intake, whereas the inverse trends in the odds of breast cancer with intake of vegetables and pulses remained after adjustment for type of diet or meat intake. These findings suggest that lifelong vegetarianism may be associated with a reduction in the risk of breast cancer through its association with a higher intake of vegetables and pulses. Although it is not possible to exclude the possibility that lifelong meat abstention may also play a role, the findings provide evidence that a diet rich in vegetables and pulses, such as those typically found in South Asian diets, may be protective against this cancer.     

2015年重庆市城乡女性乳腺癌发病及死亡现状分析

目的:了解重庆市女性乳腺癌发病与死亡现状,为开展乳腺癌防治提供建议.方法:收集整理2015年重庆市11个肿瘤登记点报告的乳腺癌(ICD-10编码为C50).采用SPSS 19.0统计分析发病率、死亡率、标化发病率、标化死亡率、构成比、顺位.不同地区间乳腺癌发病率与死亡率的比较采用χ2检验,年龄别发病率与死亡率趋势分析采用趋势χ2检验.结果:2015年11个肿瘤登记点女性乳腺癌粗发病率为31.48/10万,城市发病率(42.07/10万)高于农村(26.32/10万),差异有统计学意义(P=0.002),乳腺癌标化发病率为24.20/10万,在女性恶性肿瘤中顺位居第2位,占6.00%.女性乳腺癌粗死亡率为7.33/10万,城市(8.77/10万)与农村乳腺癌死亡率(6.62/10万)差异无统计学意义(P=0.099),乳腺癌标化死亡率为4.96/10万,在恶性肿瘤死亡顺位中居第6位,占2.10%.女性乳腺癌发病率25岁前低于5/10万,25岁后快速上升,50岁~年龄组达到高峰,随后下降.女性乳腺癌死亡率在40岁前低于5/10万,40岁后呈上升趋势,80岁~年龄组达到高峰.女性乳腺癌截缩发病率为56.01/10万,城市(67.91/10万)高于农村(50.55/10万),差异有统计学意义(P=0.001).截缩死亡率为10.75/10万,乳腺癌截缩死亡率城市(11.96/10万)与农村(10.42/10万)比较差异无统计学意义(P=0.136).发病累积危险度为2.27%,城市(3.07%)高于农村(1.93%),差异有统计学意义(P=0.039).死亡累积危险度为0.51%.结论:重庆市女性乳腺癌发病率与死亡率较高,应针对城乡女性乳腺癌发病死亡特点开展三级预防.     

Distribution of cervical and breast cancer risk factors in women and their screening behaviours

Breast cancer and cervical cancer are important causes of cancer‐related mortality in women all over the world. The present study was conducted in order to investigate the distribution of cervical and breast cancer risk factors in women and their knowledge and behaviours about cancer screening methods. The study is cross‐sectional in nature. It was conducted with the participation of 1,886 women in Turkey. Data were collected through a questionnaire. The knowledge and behaviours of women aged 40 and over about breast cancer or cervical cancer screening methods were investigated according to the education level; results showed that the rates of those who knew and did breast self‐examination were significantly lower in illiterate women. Besides, the rates of women who did breast self‐examination were significantly lower in those who were aged 40 and over, and the rates of those who had clinical breast examination and Pap smear test were significantly lower in women aged 39 and below (p < 0.01). This study identified the most notable breast and cervical cancer risk factors as low education levels, high number of deliveries, short breastfeeding period, obesity and low socio‐economic level. For this reason, public health policies should be developed to minimise these risk factors.     

Risk factors for breast cancer in Turkish women: a hospital-based case-control study

The aim of this study was to investigate the association between risk factors and breast cancer in Turkish women. In a hospital-based case-control study in Istanbul, 405 patients with histologically confirmed breast cancer were compared with 1050 controls, who were admitted to different departments of the same hospital. Unadjusted odds ratios (ORs) and 95% confidence intervals (CIs) for each risk factor were obtained from logistic regression analyses. Risk factors for breast cancer were found to be early menarche age (OR 3.87, 95% CI 2.46-6.08), use of alcohol (OR 3.87, 95% CI 1.79-8.37), history of diabetes (OR 3.31, 95% CI 2.36-4.64) or hypertension (OR 3.44, 95% CI 2.07-5.71), oral contraceptive use (OR 1.98, 95% CI 1.38-2.85) and hormone replacement therapy (HRT) use (OR 1.94, 95% CI 1.15-3.29). The findings of the present study indicated that history of diabetes or hypertension, use of alcohol, oral contraceptive and HRT, never having breastfed and delayed age at first birth associated with changing of lifestyle led to an increased risk of breast cancer in Turkish women.     

Risk factors for breast cancer: A case-control study of screen-detected breast cancer in Miyagi Prefecture, Japan

We examined the associations between reproductive factors and the risk of breast cancer on the basis of information from a total of 201,363 breast cancer screening program participants in Miyagi Prefecture, Japan, during 1987-1991. A case-control study method was applied on analysis. Data on 204 breast cancer cases identified and 810 screening year-, age- and screening area-matched normal controls were extracted. After adjustment for potential confounders, a trend of decreasing risk of breast cancer with increasing number of parity was observed (p for trend=0.03). Among parous women, lactation for the last child decreased the risk of breast cancer (odds ratio (OR) = 0.61, 95% confidence interval (95% CI) 0.39–0.94). These findings were consistent with those in clinical breast cancer reported previously. When cases were divided into two age groups, younger ( 49 y.o.) and older (50 y.o. ), family history of breast cancer among mother and sisters (OR=3.51, 95% CI 1.05–11.80), and lactation for the last child (OR=0.46, 95% CI 0.25–0.84) were associated with younger age breast cancer, whereas number of parity was associated with older age breast cancer (p for trend=0.03). The results by age group suggest that different mechanisms may exist in breast cancer developing at early and late onsets.     

Anthropometric factors in relation to different tumor biological subgroups of postmenopausal breast cancer

Overweight and obesity is associated with an increased risk of postmenopausal breast cancer. However, less is known about the impact of anthropometric factors on tumor pathology and biology. A Swedish population-based prospective cohort study of 9,685 postmenopausal women not using hormonal replacement therapy (HRT) were followed for an average of 10.3 years during which 305 incident breast cancer cases were diagnosed. Invasive and sufficient tumor material was available in 248 cases. Pathological reevaluation of histological type and grade was conducted. Using a tissue microarray (TMA), the tumor expression of Ki67, HER2, ERalpha, ERbeta, PgR, cyclin D1 and p27 was evaluated. Six anthropometric factors: height, weight, body mass index (BMI), waist- and hip circumference and body fat percentage were categorized by quartiles of baseline anthropometric measurements, and relative risks were calculated using multivariate Cox regression models. Invasive breast cancer incidence was increased for women in the higher quartiles of all anthropometric measurements. Height was positively associated with Grade I and ERalpha-positive tumors. Women in the highest quartiles of weight, BMI, waist- and hip circumference and body fat percentage were all associated with tumors of ductal type, Grade II, low Ki67 index, HER2 negativity and low expression of the oncogene cyclin D1. Obesity was further associated with tumors expressing ERalpha and PgR but interestingly not ERbeta. This study confirmed previously described associations between overweight/obesity and increased risk of postmenopausal breast cancer. Furthermore, obesity was associated with tumors expressing several markers corresponding with low malignancy.     

Effectiveness of service screening: a case-control study to assess breast cancer mortality reduction

The aim of this study was the evaluation of the impact of service screening programmes on breast cancer mortality in five regions of Italy. We conducted a matched case-control study with four controls for each case. Cases were defined as breast cancer deaths occurred not later than 31 December 2002. Controls were sampled from the local municipality list and matched by date of birth. Screening histories were assessed by the local, computerised, screening database and subjects were classified as either invited or not-yet-invited and as either screened or unscreened. There were a total of 1750 breast cancer deaths within the 50 to 74-year-old breast cancer cases and a total of 7000 controls. The logistic conditional estimate of the cumulative odds ratios comparing invited with not-yet-invited women was 0.75 (95% CI: 0.62-0.92). Restricting the analyses to invited women, the odds ratio of screened to never-respondent women corrected for self-selection bias was 0.55 (95% CI: 0.36-0.85). The introduction of breast cancer screening programmes in Italy is associated with a reduction in breast cancer mortality attributable to the additional impact of service screening over and above the background access to mammography.     

Breast cancer risk factors and a novel measure of volumetric breast density: cross-sectional study

We conducted a cross-sectional study nested within a prospective cohort of breast cancer risk factors and two novel measures of breast density volume among 590 women who had attended Glasgow University (1948-1968), replied to a postal questionnaire (2001) and attended breast screening in Scotland (1989-2002). Volumetric breast density was estimated using a fully automated computer programme applied to digitised film-screen mammograms, from medio-lateral oblique mammograms at the first-screening visit. This measured the proportion of the breast volume composed of dense (non-fatty) tissue (Standard Mammogram Form (SMF)%) and the absolute volume of this tissue (SMF volume, cm3). Median age at first screening was 54.1 years (range: 40.0-71.5), median SMF volume 70.25 cm3 (interquartile range: 51.0-103.0) and mean SMF% 26.3%, s.d.=8.0% (range: 12.7-58.8%). Age-adjusted logistic regression models showed a positive relationship between age at last menstrual period and SMF%, odds ratio (OR) per year later: 1.05 (95% confidence interval: 1.01-1.08, P=0.004). Number of pregnancies was inversely related to SMF volume, OR per extra pregnancy: 0.78 (0.70-0.86, P<0.001). There was a suggestion of a quadratic relationship between birthweight and SMF%, with lowest risks in women born under 2.5 and over 4 kg. Body mass index (BMI) at university (median age 19) and in 2001 (median age 62) were positively related to SMF volume, OR per extra kg m(-2) 1.21 (1.15-1.28) and 1.17 (1.09-1.26), respectively, and inversely related to SMF%, OR per extra kg m(-2) 0.83 (0.79-0.88) and 0.82 (0.76-0.88), respectively, P<0.001. Standard Mammogram Form% and absolute SMF volume are related to several, but not all, breast cancer risk factors. In particular, the positive relationship between BMI and SMF volume suggests that volume of dense breast tissue will be a useful marker in breast cancer studies.