Body size,weight change,fat distribution and breast cancer risk in Hispanic and non-Hispanic white women

INTRODUCTION: The incidence of breast cancer varies among women living in the Southwestern part of the US. We evaluate how body size influences breast cancer risk among these women. METHODS: Cases (n = 2,325) diagnosed with breast cancer between October 1, 1999 and May 2004 residing in Arizona, Colorado, New Mexico, or Utah were matched to controls (n = 2,525). Participants were interviewed; height, weight, waist, and hip circumference were measured at the time of interview; blood was drawn. RESULTS: A large body mass index (BMI) at age 15 was inversely associated with pre-menopausal breast cancer risk in both non-Hispanic white (NHW) and Hispanic women (Odds ratio, ORs 0.68 95% CI 0.44, 1.04, and 0.65 95% CI 0.39, 1.08, respectively); BMI at age 15 also had an impact on subsequent breast cancer associated with obesity after menopause. Among post-menopausal women, recent exposure to hormones was an important modifier of risk associated with body size. Among women not recently exposed to hormones risk associated with obesity was 1.61 (95% CI 1.05, 2.45) for NHW women; gaining > or = 25 kg between 15 and age 50 was inversely associated with breast cancer among Hispanic women (OR 0.51, 95% CI 0.23, 1.14). A large weight gain and a large waist-to-hip ratio (WHR) was associated with an increased odds of having an estrogen receptor negative tumor among NHW only (OR 1.81, 95% CI 1.07, 3.08, and 2.04 95% CI 1.20,3.50). CONCLUSIONS: These findings suggest that the metabolic consequences of obesity on breast cancer risk differ between NHW and Hispanic women living in the Southwest.     

Obstetric history and mammographic density: a population-based cross-sectional study in Spain (DDM-Spain)

High mammographic density (MD) is used as a phenotype risk marker for developing breast cancer. During pregnancy and lactation the breast attains full development, with a cellular-proliferation followed by a lobular-differentiation stage. This study investigates the influence of obstetric factors on MD among pre- and post-menopausal women. We enrolled 3,574 women aged 45-68 years who were participating in breast cancer screening programmes in seven screening centers. To measure MD, blind anonymous readings were taken by an experienced radiologist, using craniocaudal mammography and Boyd's semiquantitative scale. Demographic and reproductive data were directly surveyed by purpose-trained staff at the date of screening. The association between MD and obstetric variables was quantified by ordinal logistic regression, with screening centre introduced as a random effect term. We adjusted for age, number of children and body mass index, and stratified by menopausal status. Parity was inversely associated with density, the probability of having high MD decreased by 16% for each new birth (P value < 0.001). Among parous women, a positive association was detected with duration of lactation [>9 months: odds ratio (OR) = 1.33; 95% confidence interval (CI) = 1.02-1.72] and weight of first child (>3,500 g: OR = 1.32; 95% CI = 1.12-1.54). Age at first birth showed a different effect in pre- and post-menopausal women (P value for interaction = 0.030). No association was found among pre-menopausal women. However, in post-menopausal women the probability of having high MD increased in women who had their first child after the age of 30 (OR = 1.53; 95% CI = 1.17-2.00). A higher risk associated with birth of twins was also mainly observed in post-menopausal women (OR = 2.02; 95% CI = 1.18-3.46). Our study shows a greater prevalence of high MD in mothers of advanced age at first birth, those who had twins, those who have breastfed for longer periods, and mothers whose first child had an elevated birth weight. These results suggest the influence of hormones and growth factors over the proliferative activity of the mammary gland.     

Body size indices and breast cancer risk before and after menopause

The relationship between various body size indices and breast cancer risk before and after menopause was elucidated by means of a case-control study conducted between June 1991 and April 1994 in 6 Italian centers on 2,569 patients aged below 75 with histologically confirmed breast cancer, and on 2,588 controls admitted to the hospital for a wide spectrum of acute, non-neoplastic, non-hormone-related diseases. Weight and, more consistently, body mass index (BMI, kg/m²) at diagnosis were inversely related to pre-menopausal breast cancer risk and directly to post-menopausal risk. An 8-unit increase in BMI resulted in an odds ratio of 0.8 for pre-menopausal and of 1.2 (significant) for post-menopausal women. Risk seemed to increase gradually after menopause in the 7th (OR for an 8-unit BMI increase, 1.3) and 8th decades (OR, 1.6) of life. Conversely, height, waist-to-hip ratio, bra cup size and weight (or BMI) in adolescence and in young adulthood did not exert a significant or consistent influence on breast cancer risk. The apparent relationship with BMI at middle age and weight gain between age 30 years and diagnosis was eliminated by allowance for BMI at diagnosis. The age-related pattern of the association between BMI and breast cancer risk after menopause may reflect a duration-risk relationship, and resembles the effect of post-menopausal estrogen use, which seems greater among older women. © 1996 Wiley-Liss, Inc.     

Lifetime exercise activity and breast cancer risk among post-menopausal women.

Lifetime exercise activity has been linked to breast cancer risk among young women. However, no study has specifically evaluated whether lifetime exercise activity is related to the breast cancer risk of post-menopausal women. We conducted a population-based case-control study of post-menopausal white women (1123 newly diagnosed cases and 904 healthy controls) aged 55-64 who lived in Los Angeles County, California, USA to evaluate this relationship. Although neither exercise activity from menarche to age 40 years, nor exercise after age 40 separately predicted breast cancer risk, risk was lower among women who had exercised each week for at least 17.6 MET-hours (metabolic equivalent of energy expenditure multiplied by hours of activity) since menarche than among inactive women (odds ratio (OR) = 0.55; 95% confidence interval (CI) 0.37-0.83). Exercise activity was not protective for women who gained considerable (> 17%) weight during adulthood. However, among women with more stable weight, breast cancer risk was substantially reduced for those who consistently exercised at high levels throughout their lifetime (OR = 0.42; 95% CI 0.24-0.75), those who exercised more than 4 h per week for at least 12 years (OR = 0.59; 95% CI 0.40-0.88), and those who exercised vigorously (24.5 MET-hours per week) during the most recent 10 years (OR = 0.52; 95% CI 0.32-0.85). Strenuous exercise appears to reduce breast cancer risk among post-menopausal women who do not gain sizable amounts of weight during adulthood.     

Association of body size and fat distribution with risk of breast cancer among Chinese women.

Most previous studies addressing the association of body size, weight change and body fat distribution with the risk of breast cancer were conducted in Western societies with a high proportion of overweight people. It remains unclear whether the dose-response relation observed in earlier studies can be extended to women with "normal" weight based on prevailing Western standards. To address this issue, we analyzed data from a population-based case-control study of breast cancer recently completed among Chinese women in urban Shanghai. In-person interviews and anthropometric measurements were completed for 1,459 women newly diagnosed with breast cancer from 25 to 64 years of age and 1,556 controls frequency-matched to cases on age. Unconditional logistic regression was employed to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CI) related to anthropometric variables and self-reported body weight. Currently measured weight, body mass index [BMI: weight (kg)/height(m)(2)] or height was each found to be positively related to risk of postmenopausal breast cancer in a dose-response manner, with ORs (95% CI) being 2.0 (1.4-3.0), 2.0 (1.2-3.2) or 1.7 (1.2-2.5), respectively, for the highest category of weight, BMI or height compared to the lowest category of these variables. These variables were unrelated to premenopausal breast cancer risk. Reported weight at ages >40 years and weight gain after age 20 were more predictive for postmenopausal breast cancer than weight at an earlier age. After adjustment for BMI, waist-to-hip ratio was related to an increased risk of premenopausal [OR = 1.7 (1.3-2.3) for the highest category compared to the lowest category] but not postmenopausal breast cancer. This study suggests that, even in a relatively thin Chinese population, weight gain and height are related to an increased risk of postmenopausal breast cancer, while central fat distribution was associated with premenopausal breast cancer. General weight control may be an effective measurement for breast cancer prevention.     

Association of gain and loss of weight before and after menopause with risk of postmenopausal breast cancer in the Iowa women's health study.

Obesity and adult weight gain are well-established risk factors for postmenopausal breast cancer. Although there are a few studies demonstrating the contribution of adult weight gain to breast cancer risk, whether weight gain during a critical time period is specifically associated with risk, or whether subsequent weight loss among women who have gained weight will reduce the excess risk, is not firmly established. We investigated the association of changes in weight (loss or gain in excess of 5% of body weight) using two risk factor models: (a) age 18 to 30 years and age 30 years to menopause and (b) age 30 years to menopause and after the menopause to the baseline study in 1986 on risk of postmenopausal breast cancer in a prospective cohort of 33,660 postmenopausal women in Iowa. Over 15 years of follow-up, 1,987 cases of breast cancer occurred. Data were analyzed using proportional hazards regression models adjusted for established breast cancer risk factors. The most frequently observed pattern of body weight over time was a consistent increase; these women were observed to have the highest rates of breast cancer and served as the reference category for all comparisons. The lowest-risk groups were (a) women who maintained or lost weight from age 18 to 30 years and then lost weight from age 30 years to menopause [risk ratio (RR), 0.36; 95% confidence interval (95% CI), 0.22-0.60] and (b) women who maintained or lost weight from age 30 years to menopause and then lost weight after the menopause (RR, 0.48; 95% CI, 0.22-0.65). Women who gained weight from age 30 years to menopause but then lost weight after the menopause experienced risk reductions (RR, 0.77; 95% CI, 0.64-0.92) although perhaps slightly smaller in magnitude than women who maintained their weight in both time intervals (RR, 0.63; 95% CI, 0.55-0.73). Women who gained weight from age 18 to 30 years and then lost weight from age 30 years to menopause had comparable risk reductions (RR, 0.61; 95% CI, 0.46-0.8) with women who maintained their weight in both time intervals (RR, 0.73; 95% CI, 0.64-0.84). Women who gained weight during the period from age 30 years to menopause but who had stable weight after menopause had rates similar to the reference group. These data suggest prevention of weight gain between age 18 years and menopause or weight loss and maintenance during these years reduces risk of postmenopausal breast cancer.     

Adolescent diet and breast cancer in Utah

A population-based case-control study was conducted to assess the association between breast cancer risk, body mass index (BMI) and adolescent dietary fat and fiber consumption. Data were collected in Utah from white female cases (N = 172) and controls (N = 190) between the ages of 20 and 54 years. Odds ratios (OR) and 95% test-based confidence intervals (CI) were determined by multiple-logistic regression analysis controlling for age, education, age at menarche, and age at first pregnancy. Menopausal status was identified as an effect modifier, therefore, separate analyses were performed for pre and postmenopausal groups. An elevated risk (OR = 2.9 for highest quartile versus lowest, CI = 1.1-8.1) was associated with a larger BMI at age 12 in premenopausal women; a larger adult BMI lowered the odds ratio (OR = 0.4, CI = 0.2-1.0 for highest quartile versus lowest) in premenopausal women; BMI did not alter risk in postmenopausal women. Although not statistically significant, high fat intake consistently lowered the odds ratios below 1.0 in premenopausal women in the upper three quartiles compared to the lowest fat intake referent quartile (OR = 0.7, CI = 0.2-2.1 for highest versus lowest quartile) but was inconsistent in postmenopausal women (OR = 0.7, CI = 0.2-2.7 for highest versus lowest quartile). When fat intake was assessed by its component parts, fat from milk, cheese and yogurt reduced the odds ratios in both premenopausal (OR = 0.4, CI = 0.1-1.1 for highest versus lowest quartile) and postmenopausal women (OR = 0.2, CI = 0.0-0.8). In postmenopausal women, high fiber intake produced elevated odds ratios in all three upper quartiles (OR = 6.6, CI = 1.5-29.6 for highest versus lowest quartile), while fiber from grains resulted in a decreased risk in both premenopausal (OR = 0.2, 95% CI = 0.2-0.7 for highest versus lowest quartile) and postmenopausal women (OR = 0.7, 95% CI = 0.3-2.0). The possibility of biased estimates from low response rates (cases = 60%, controls = 61%), potential recall bias, and some lack of precision in the dietary instrument should be considered. It appears from these analyses that the relation of breast cancer to dietary intake, especially during adolescent years, is not clear, and that risk associated with fat or fiber intake may be affected by the nutrient source.     

Obesity,weight gain,and ovarian cancer risk in African American women

Although there is growing evidence that higher adiposity increases ovarian cancer risk, little is known about its impact in African American (AA) women, the racial/ethnic group with the highest prevalence of obesity. We evaluated the impact of body mass index (BMI) 1 year before diagnosis and weight gain since age 18 years on ovarian cancer risk in a population‐based case‐control study in AA women in 11 geographical areas in the US. Cases (n = 492) and age and site matched controls (n = 696) were identified through rapid case ascertainment and random‐digit‐dialing, respectively. Information was collected on demographic and lifestyle factors, including self‐reported height, weight at age 18 and weight 1 year before diagnosis/interview. Multivariable logistic regression was used to compute odds ratios (OR) and 95% confidence intervals (CI), adjusting for potential covariates. Obese women had elevated ovarian cancer risk, particularly for BMI ≥ 40 kg/m² compared to BMI <25 (OR = 1.72, 95% CI: 1.12‐2.66; p for trend: 0.03). There was also a strong association with weight gain since age 18 (OR: 1.52; 95% CI: 1.07–2.16; p for trend: 0.02) comparing the highest to lowest quartile. In stratified analyses by menopausal status, the association with BMI and weight gain was limited to postmenopausal women, with a 15% (95% CI: 1.05–1.23) increase in risk per 5 kg/m² of BMI and 6% (95% CI: 1.01–1.10) increase in risk per 5 kg of weight gain. Excluding hormone therapy users essentially did not change results. Obesity and excessive adult weight gain may increase ovarian cancer risk in post‐menopausal AA women.     

Anthropometric factors and breast cancer risk among urban and rural women in South India: a multicentric case-control study

Breast cancer (BC) incidence in India is approximately twice as high in urban women than in rural women, among whom we investigated the role of anthropometric factors and body size. The study was conducted at the Regional Cancer Centre, Trivandrum, and in three cancer hospitals in Chennai during 2002-2005. Histologically confirmed cases (n=1866) and age-matched controls (n=1873) were selected. Anthropometric factors were measured in standard ways. Information on body size at different periods of life was obtained using pictograms. Odds ratios (OR) of BC were estimated through logistic regression modelling. Proportion of women with body mass index (BMI)>25.0 kg/m(2), waist size >85 cm and hip size >100 cm was significantly higher among urban than rural women. Risk was increased for waist size >85 cm (pre-menopausal: OR=1.24, 95% CI: 0.96-1.62; post-menopausal: 1.61, 95% CI: 1.22-2.12) and hip size >100 cm (pre-menopausal: OR=1.47, 95% CI: 1.05-2.06; post-menopausal 2.42, 95% CI: 1.72-3.41). Large body size at age 10 (OR=1.75, 95% CI: 1.01-3.03) and increased BMI (OR=1.33, 95% CI: 1.05-1.69 for 25.0-29.9 kg/m(2) and OR=1.56, 95% CI: 1.03-2.35 for 30+ kg/m(2)) were associated with pre-menopausal BC risk. Our data support the hypotheses that increased anthropometric factors are risk factors of BC in India.     

Age at menarche, age at menopause, height and obesity as risk factors for breast cancer: associations and interactions in an international case-control study

The importance of age at menarche, age at menopause, height, and obesity as risk factors for breast cancer, and the possible interactions among these factors in breast cancer causation were investigated in a data set collected in the late 1960's, in an international multicenter case-control study. Multiple logistic regression procedures were used to model data from 3,993 breast cancer cases and 11,783 controls from 7 study centers representing the range of international variation of breast cancer incidence. Height and obesity (measured through the weight/height2 index) were independent risk factors for breast cancer among post-menopausal but not pre-menopausal women; post-menopausal women taller by 10 cm had a 12% higher risk of breast cancer (95% confidence interval, CI, 3-21%) and post-menopausal women of average height (say 158 cm) had an 11% higher risk of breast cancer (CI 7-16%) when they were heavier by 10 kg (and, therefore, more obese by 4 kg/m2). Age at menarche was a risk factor among both pre-menopausal and post-menopausal women, a delay of 2 years corresponding to a 10% reduction in breast cancer risk (CI 6-15%). Age at menopause was also a breast cancer risk factor, women with menopause at each 5 year age difference having a 17% higher risk of breast cancer (CI 11-22%). There is evidence of an interaction (deviation from the logistic regression-postulated multiplicativity) between obesity and age at menarche, implying that the protective effect of late menarche may not apply to overweight women or that late menarche may become detrimental in obese women. The estimated relative risk coefficients, when applied to average risk factor levels observed among control women, can explain only a small fraction of the difference in breast cancer incidence between Boston and Tokyo.     

Risk Factor Analysis for Breast Cancer in Premenopausal and Postmenopausal Women of Punjab,India

Objective: Amritsar, the second largest town of agrarian state of Punjab, India reports high number of breast cancer cases every year. The present study investigated the etiology of breast cancer using various obesity indices and other epidemiological factors among breast cancer patients residing in and around Amritsar city. Methods: In this case control study, risk factors for breast cancer were analyzed in 542 female subjects: 271 females with breast cancer patients and 271 unrelated healthy females matched for age as control females. Results: Bivariate analysis for risk factors in cases and controls showed a lower risk (OR=0.65, 95% CI 0.43-0.99, p=0.04) in obese cases with BMI≥25kg/m2 as compared to subjects with normal BMI. Risk factor analysis showed that parameter which provided risk for cancer in postmenopausal women was obesity and in premenopausal women was parity. Postmenopausal women with BMI (overweight: OR=0.39, 95% CI 0.17-0.92, p=0.03; obese: OR= 0.26, 95% CI 0.13-0.52, p=0.00), WC (OR=0.17, 95% CI 0.05-0.52, p=0.00) and WHtR (p=0.02) had highr risk. Premenopausal women with 3 or less than 3 children had a higher risk (OR=5.54, 95 % CI 2.75-11.19, p=0.00) than postmenopausal women when compared to women with more than 3 children. Binary logistic regression analysis revealed that low parity (≤3) substantially increased the risk for breast cancer (OR=4.80, 95% CI 2.34-9.85, p=0.00) in premenopausal women. Conclusion: Obesity, parity associated breast cancer risk and reduced breastfeeding cumulatively predispose the premenopausal women of this region to higher risk of breast cancer.     

Mammographic density and risk of breast cancer by adiposity: an analysis of four case-control studies

The association of mammographic breast density with breast cancer risk may vary by adiposity. To examine effect modification by body mass index (BMI), the authors standardized mammographic density data from four case-control studies (1994-2002) conducted in California, Hawaii and Minnesota and Gifu, Japan. The 1,699 cases and 2,422 controls included 45% Caucasians, 40% Asians and 9% African-Americans. Using ethnic-specific BMI cut points, 34% were classified as overweight and 19% as obese. A single reader assessed density from mammographic images using a computer-assisted method. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals (95% CI) while adjusting for potential confounders. Modest heterogeneity in the relation between percent density and breast cancer risk across studies was observed (p(heterogeneity) = 0.08). Cases had a greater age-adjusted mean percent density than controls: 31.7% versus 28.5%, respectively (p <0.001). Relative to <20 percent density, the ORs for >35 were similar across BMI groups whereas the OR for 20-35 was slightly higher in overweight (OR = 1.69, 95% CI: 1.28, 2.24) and obese (OR = 1.62, 95% CI: 1.12, 2.33) than in normal weight women (OR = 1.49, 95% CI: 1.11, 2.01). Furthermore, limited evidence of effect modification by BMI of the OR per 10% increase in percent density (p(interaction) = 0.06) was observed, including subgroup analyses by menopausal status and in analyses that excluded women at the extremes of the BMI scale. Our findings indicate little, if any, modification by BMI of the effects of breast density on breast cancer risk.     

Early-life physical activity and postmenopausal breast cancer: effect of body size and weight change.

It is not yet known whether early-life physical activity reduces the risk of developing breast cancer. Subgroup analyses according to menopausal status and body mass may help clarify this association. Data from a population-based case-control study of female residents of Wisconsin, Massachusetts, Maine, and New Hampshire were used to examine associations between body mass and breast cancer risk. Cases (n = 4614) were identified by each state's tumor registry; controls (n = 5817) were randomly selected from population lists. Frequency of participation in strenuous physical activity when 14-22 years of age, weight at age 18 and 5 years before interview, height, and other factors were ascertained through structured telephone interviews. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were computed using logistic regression. Reductions in postmenopausal breast cancer risk associated with strenuous physical activity were greatest for women in the fourth quartile of body mass index at age 18; the OR for women with the highest activity frequency on average (> or =once/day) was 0.45 (95% CI = 0.26-0.79). Associations with frequency of activity also varied by weight change. Compared to women with no activity and little adult weight gain, frequent physical activity was associated with reduced postmenopausal breast cancer risk in women who had lost weight since age 18 (OR = 0.19, 95% CI = 0.05-0.70) or had gained little or modest amounts of weight (weight gain: first tertile, OR = 0.36, 95% CI = 0.05-0.85; second tertile, OR = 0.31, 95% CI = 0.14-0.66). Weighted MET score analyses yielded similar but less inverse results. These findings suggest that the reduced risk of postmenopausal breast cancer associated with frequent, early-life physical activity may be greatest in women who, over the adult years, either lost weight or gained only modest amounts.     

Marine n-3 fatty acid intake, glutathione S-transferase polymorphisms and breast cancer risk in post-menopausal Chinese women in Singapore

We have previously found marine n-3 fatty acids to be inversely related to post-menopausal breast cancer in Chinese women from Singapore. Post-menopausal women with high [quartiles 2-4 (Q2-Q4)] versus low [quartile 1 (Q1)] intake exhibited a statistically significant reduction in risk of breast cancer after adjustment for potential confounders [relative risk (RR) = 0.66, 95% confidence interval (CI) = 0.50, 0.87]. Experimental studies have demonstrated a direct role for the peroxidation products of marine n-3 fatty acids in breast cancer protection. There is a suggestion that the glutathione S-transferases (GSTs) may be major catalysts in the elimination of these beneficial by-products. Therefore, we hypothesized that individuals possessing the low activity genotypes of GSTM1, GSTT1 and/or GSTP1 (i.e. the GSTM1 null, GSTT1 null and GSTP1 AB/BB genotypes, respectively) may exhibit a stronger marine n-3 fatty acid-breast cancer association than their high activity counterparts. The Singapore Chinese Health Study is a prospective investigation involving 35,298 middle-aged and older women, who were enrolled between April 1993 and December 1998. In this case-control analysis, nested within the Singapore Chinese Health Study, we compared 258 incident breast cancer cases with 670 cohort controls. Overall, breast cancer risk was unrelated to GSTM1 and GSTP1 genotypes. However, the GSTT1 null genotype was associated with a 30% reduced risk of breast cancer [odds ratio (OR) = 0.71, 95% CI = 0.52, 0.96]. Among women with high activity GST genotypes (i.e. GSTM1 positive, GSTT1 positive and GSTP1 AA), no marine n-3 fatty acid-breast cancer relationships were observed in either pre-menopausal or post-menopausal women at baseline. However, post-menopausal women possessing the combined GSTM1 null and GSTP1 AB/BB genotypes showed a statistically significant reduction in risk after adjustment for potential confounders (Q2-Q4 versus Q1, OR = 0.36, 95% CI = 0.14, 0.94). A similar relationship was observed among women with the combined GSTT1 null and GSTP1 AB/BB genotypes (OR = 0.26, 95% CI = 0.08, 0.78).     

Diet, alcohol consumption and reproductive factors in a case-control study of breast cancer in Moscow

A case-control study was conducted in Moscow to assess the effect of diet on risk of breast cancer, and also to study the established reproductive risk factors. A notable finding of the study, which covered 139 case-control pairs matched by age and neighbourhood, is that dietary factors are more important for post-menopausal than for pre-menopausal breast cancer. The decreased risk of post-menopausal breast cancer was associated with high intakes of cellulose (OR 0.04; 95% CI 0.01-0.31), mono- and disaccharides (OR 0.02; 95% CI 0.002-0.27), vitamin C (OR 0.20; 95% CI 0.06-0.70), beta-carotene (OR 0.09; 95% CI 0.02-0.49), and also polyunsaturated fatty acids (OR 0.14; 95% CI 0.03-0.69). High intakes of total fat resulted in a statistically non-significant decrease in the odds ratio (OR 0.52; 95% CI 0.04-6.99), while saturated fats slightly increased the risk of breast cancer (OR 1.67; 95% CI 0.24-11.78). Protein intake was also associated with increased risk of breast cancer (OR 4.62; 95% CI 0.69-30.70). Alcohol use significantly increased the risk of breast cancer in postmenopausal women (OR 3.39; 95% CI 1.37-8.38). In general, the results of our study indicate that high risk of breast cancer is associated with high intakes of nutrients derived from animal products, and low risk with high intake of those from vegetables and fruits.     

Long-term weight change and breast cancer risk: the European prospective investigation into cancer and nutrition (EPIC)

We examined prospectively the association between weight change during adulthood and breast cancer risk, using data on 1358 incident cases that developed during 5.8 years of follow-up among 40,429 premenopausal and 57,923 postmenopausal women from six European countries, taking part in the European prospective investigation into cancer and nutrition study. Multivariate Cox regression models were used to calculate hazard ratios according to weight change (kg), defined as the weight difference between age at enrollment and age 20 adjusted for other risk factors. Changes in weight were not associated with premenopausal breast cancer risk. In postmenopausal women, weight gain was positively associated with breast cancer risk only among noncurrent hormone replacement therapy (HRT) users (P-trend < or = 0.0002). Compared to women with a stable weight (+/-2 kg), the relative risk for women who gained 15-20 kg was 1.50 (95% confidence interval (CI) 1.06-2.13). The pooled RR per weight gain increment of 5 kg was 1.08 (95% CI 1.04-1.12). Weight gain was not associated with breast cancer risk in current HRT users, although, overall, these women experienced a much higher risk of breast cancer compared with nonusers. Our findings suggest that large adult weight gain was a significant predictor of breast cancer in postmenopausal women not taking exogenous hormones.     

A prospective study of adiposity and postmenopausal breast cancer risk: the Malmö Diet and Cancer Study

High BMI is a well-known risk factor for postmenopausal breast cancer. There have been some reports of excess risk in association with weight gain and WHR, but little is known about the influence of body fatness per se. Using data from the Malm? Diet and Cancer Study, a prospective cohort study, 12,159 postmenopausal women (59.9 +/- 7.7 years) were categorized by quintiles of baseline anthropometric and impedance measures and reported weight change since age 20. RRs from multivariate Cox regression models were calculated. All analyses were adjusted for age, height, smoking, alcohol consumption, occupation, marital status, parity, age at first pregnancy, age at menarche and current hormone use. During the 5.7 years of follow-up, there were 246 incident breast cancer cases. Weight, height, BMI and %BF were positively associated with risk of breast cancer (p(trend) 21 kg (top quintile) had an RR of 1.75 (95% CI 1.11-2.77) compared to women with low weight gain. Breast cancer risk in postmenopausal women is predicted by increased body fat and weight gain. %BF is a more discriminating risk factor for breast cancer incidence than the commonly used BMI.     

Risk factors for hormone receptor-defined breast cancer in postmenopausal women.

The effect of classic breast cancer risk factors on hormone receptor-defined breast cancer is not fully clarified. We explored these associations in a Swedish population-based study. Postmenopausal women ages 50 to 74 years, diagnosed with invasive breast cancer during 1993 to 1995, were compared with 3,065 age frequency-matched controls. We identified 332 estrogen receptor (ER-) and progesterone receptor (PR-) negative, 286 ER+PR-, 71 ER-PR+, 1,165 ER+PR+, and 789 tumors with unknown receptor status. Unconditional logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (95% CI). Women ages >or=30 years, compared with those ages 20 to 24 years at first birth, were at an increased risk of ER+PR+ tumors (OR, 1.5; 95% CI, 1.2-1.8) but not ER-PR- tumors (OR, 1.1; 95% CI, 0.8-1.6). Women who gained >or=30 kg in weight during adulthood had an approximately 3-fold increased relative risk of ER+PR+ tumors (OR, 2.7; 95% CI, 1.9-3.8), but no risk increase of ER-PR- tumors (OR, 1.0; 95% CI, 0.5-2.1), compared with women who gained <10 kg. Compared with never users, women who used menopausal estrogen-progestin therapy for at least 5 years were at increased risk of ER+PR+ tumors (OR, 3.0; 95% CI, 2.1-4.1) but not ER-PR- tumors (OR, 1.3; 95% CI, 0.7-2.5). In conclusion, other risk factors were similarly related to breast cancer regardless of receptor status, but high age at first birth, substantial weight gain in adult age, and use of menopausal estrogen-progestin therapy were more strongly related to receptor-positive breast cancer than receptor-negative breast cancer.     

Effect of body size on breast‐cancer risk among Japanese women

With the use of data from the hospital‐based epidemiologic research program at Aichi Cancer Center (HERPACC), the effect of body size on the risk of breast cancer was evaluated among Japanese women, who are generally leaner than white women. In total, 1,359 breast‐cancer cases were included, and 24,207 women, confirmed as free of cancer, were recruited as a reference group. Odds ratios (OR) and 95% confidence intervals (95% CI) were determined by multiple‐logistic regression analysis. Separate analyses were performed for pre‐ and post‐menopausal women. Furthermore, stratification by decade of age was done to evaluate the effect of body size on the development of breast cancer. The results obtained from the present study were as follows. (1) Current body‐mass index (BMI) was positively associated with post‐menopausal breast cancer (OR 2.08, 95% CI 1.49–2.92 for highest quintile vs. lowest), although higher BMI did not affect the risk in pre‐menopausal women. (2) Estimates of risk were below unity for BMI at around age 20 in post‐menopausal women. (3) After stratifying BMI at around age 20, gaining BMI in later life was positively associated with increased risk, regardless of BMI in early life. These findings suggest that avoidance of marked weight gain during adult life, especially after natural menopause and/or after age 60, may reduce the risk of breast cancer. Int. J. Cancer 80:349–355, 1999. © 1999 Wiley‐Liss, Inc.     

Body mass index and post-menopausal breast cancer: an age-specific analysis.

The relationship between body mass index (BMI, Quetelet''s index, kg m(-2)) and post-menopausal breast cancer risk was considered in age-specific strata on the basis of a pooled analysis of three Italian case-control studies, including a total of 3108 post-menopausal breast cancer patients aged 50 years or over and 2664 control subjects. Overall, there was a moderate, but significant, association between BMI and post-menopausal breast cancer: the odds ratios (ORs) were around 1.3 for the three intermediate quintiles compared with the lowest one, and 1.4 for the highest one. The association was moderate among women aged 50-59 years and 60-69 years, with ORs around 1.3 for the highest BMI quintiles, but stronger among elderly women, with ORs of 1.6 for the fourth and 2.1 for the fifth quintile. An 8-unit increase in BMI involved an OR of 1.18 at age 50-59 years, of 1.14 at age 60-69 years and of 1.59 above age 70 years. This pattern of risk is similar to that observed for post-menopausal hormone replacement treatment and is consistent with a duration-risk relationship in the exposure to high oestrogen levels and with a greater differential in oestrogen levels in overweight elderly women. In terms of population attributable risk, 19.6% of all post-menopausal breast cancer patients and 27.1% of those in women above age 70 years were attributable to overweight and obesity in this population. This has, therefore, major preventive implications as to reduce breast cancer risk late in life, it is essentially important to control weight gain in elderly women.