Anthropometric variables and risk of breast cancer

Development and validation study of the breast cancer risk appraisal for Korean women

The purpose of the present study was to develop and validate breast cancer risk factors, which can be used to identify women who are at a high risk of developing breast cancer. Fourteen risk factors for breast cancer were identified from extensive literature reviews and in consultation with a panel of experts. A case-control study was conducted, which aimed to validate these 14 risk factors. Cases were selected from four university hospitals in Korea and controls were selected from health screening centers in Korea. Interviews were used to obtain exposure history of each participant to the 14 risk factors. Group differences between the cases and controls were analyzed using a chi-squared test and a logistic regression method. Among the 14 risk factors, six were identified as significant: meat consumption more than once a week (odds ratio [OR] = 1.56, confidence interval [CI] = 1.32-1.85), breast disease experience (OR = 3.08, CI = 1.49-6.37), less than two children (OR = 1.61, CI = 1.09-2.35), family history of breast cancer (OR = 8.99, CI = 3.89-20.76), and no breast-feeding experience (OR = 3.08, CI = 1.41-3.85). Based on the OR, the risk scores were calculated by the absolute size of the OR having a total of 100 points.

Exposures in childhood, adolescence and early adulthood and breast cancer risk: a systematic review of the literature

A growing body of work indicates that exposures over the life course have important roles to play in the aetiology of breast cancer. This review synthesises the literature that has been published in the area of early life events and female breast cancer risk. The review finds some evidence, primarily from cohort studies on the relationship between birthweight and breast cancer, to suggest that in utero events are related to breast cancer risk in adulthood. Strong evidence to support a positive association between height and breast cancer exists. Postulated mechanisms for this relationship include the role of early diet in subsequent disease risk, and the influence of endogenous growth factors mediating the relationship. There is some evidence to suggest that leg length is the component of height which is generating the observed associations between height and breast cancer. There is no consistent pattern of association between relative weight in childhood or adolescence and risk of breast cancer. The evidence to suggest an association between physical activity in early life and breast cancer risk is convincing from case-control studies, but is not fully substantiated by the results of three cohort studies. There are inconsistent results regarding the association between smoking at a young age and breast cancer risk. There is little evidence for an association between passive smoking in early life and breast cancer risk. No clear association between early drinking and breast cancer risk exists. These results are discussed in relation to possible underlying mechanisms and health promotion strategies which could reduce breast cancer risk.

Risk factors for breast cancer in Japan, with special attention to anthropometric measurements and reproductive history

BACKGROUND

Breast cancer incidence has increased rapidly in Japan recently, but there have been only a few studies on the risk factors for breast cancer in Japan. A case-control study was conducted to evaluate the roles of anthropometric and reproductive factors in the etiology of breast cancer in Osaka.

METHODS

Based on information from a self-administered questionnaire at Osaka Medical Center for Cancer and Cardiovascular Diseases, body mass index, body weight and height were compared between 376 cases and 430 controls, together with other factors such as age at menarche, age at first delivery and family history of breast cancer by menopausal status. Logistic regression analysis was employed for adjusting confounding factors and estimating odds ratios with their 95% confidence interval for breast cancer.

RESULTS

A body mass index of >25 was significantly associated with the risk among post-menopausal women (age-adjusted odds ratio: 1.90, 95% confidence interval: 1.10-3.24) as compared with the risk for a body mass index of < or = 20. A weight of > or =58 kg showed significantly increased risk compared with a weight of < or = 47 kg among post-menopausal women (1.83, 1.10-3.01), while height of > or = 159 cm showed a significantly elevated risk than height of < or = 149 cm among pre-menopausal women (2.51, 1.17-5.39). Age at menarche of < or = 13 years resulted in a higher risk of breast cancer among post-menopausal women, while age at first delivery of > or = 28 years was associated with the risk among pre-menopausal women. Family history of breast cancer was associated with the risk for breast cancer.

CONCLUSIONS

These results were all very consistent with findings observed in western countries.

A woman's build and the risk of breast cancer

A woman's build and the risk of breast cancer seem to be related. While relative overweight, as described by the body mass index, seems to be associated with increased breast cancer risk in postmenopausal women, overweight in premenopausal women seems slightly protective. Papers from a MEDLINE search are reviewed regarding the association between build and the development of breast cancer. Different aspects of build, such as height, weight, body mass index and body shape, are discussed. The more prominent associations found through this search are a positive association between height and breast cancer risk both in pre- and postmenopausal women. Regarding body mass index, the association is negative in premenopausal women and positive in postmenopausal women. Body shape described as masculine versus feminine seems to have no impact on breast cancer risk in premenopausal women, but seems to be positively associated with breast cancer in postmenopausal women. Possible biological mechanisms responsible for the associations with breast cancer risk are discussed, including endogenous oestrogens, androgens and glucose metabolic substances. Avoiding or reducing postmenopausal overweight may modify breast cancer risk indicators in a more favourable direction.

Height and breast cancer risk

The relationship between adult height and breast cancer risk was considered, combining data from two case-control studies, one conducted between 1983 and 1991 in northern Italy and the other between 1991 and 1994 in six Italian centres. Cases were 5984 women, below the age of 75 years, with histologically confirmed breast cancer, and controls were 5504 women admitted to hospital for a wide spectrum of acute, non-neoplastic, non-hormone-related diseases. No relationship was observed between height and the risk of breast cancer, with a multivariate odds ratio (OR) of 0.96 (95% confidence intervals (CI) 0.85-1.08) for the tallest women (height > or = 166 cm) compared with the shortest (height < 156 cm). No significant heterogeneity was found across strata of age at diagnosis, education, body mass index, body weight, alcohol intake, age at menarche and menopause, parity, age at first birth, ever use of oral contraceptives and hormone replacement therapy, history of benign breast disease and family history of breast cancer. Thus, this study indicates that adult height is not appreciably related to breast cancer risk in this Italian population.

Risk factors for breast carcinoma in Singaporean Chinese women: the role of central obesity

BACKGROUND

The incidence of breast carcinoma in Singapore has nearly doubled over the past 25 years. This prospective case-control study involving 1086 women (204 cases and 882 controls) was conducted to determine significant factors associated with the risk of breast carcinoma among Chinese women in Singapore ages 45 to 69 years.

METHODS

A forward stepwise logistic regression model adjusted for confounding variables of age, age at menarche, menopausal status, parity, age at first and last delivery, use of oral contraceptives, hormone replacement therapy, family history of breast carcinoma, history of benign breast biopsy, smoking history, height, weight, body mass index, and waist to hip ratio was used.

RESULTS

Central obesity as indicated by women with a larger waist to hip ratio was associated with highest risk for breast carcinoma (odds ratio [OR]: 9.18; 95% confidence interval [CI],4.8-17.5 comparing last and first quintile; P < 0.0001, chi-square test for trend). Significant trends were also noted for increasing height and breast carcinoma risk (P = 0.003, chi-square test). Women who were taller than 159 cm (OR: 2.3; 95% CI, 1.4-3.9) had approximately twice the risk of women shorter than 150 cm. Body mass index as a measure of generalized obesity did not significantly predict risk for breast carcinoma. Reproductive and menstrual factors significantly related to risk for breast carcinoma were number of deliveries (OR: 0.81; 95% CI, 0.7-0.9; P < 0.001), age at last delivery (P = 0.03), and use of hormone replacement therapy (OR: 0.54; 95% CI, 0.3-0.9; P = 0.01). Previous breast biopsy for benign disease was also associated with a higher risk for breast carcinoma (OR: 3.5; 95% CI, 2.1-5.7; P < 0.001).

CONCLUSIONS

The authors conclude that the risk of breast carcinoma is strongly associated with changes in lifestyle related to caloric intake (central obesity and height) and reproductive or menstrual factors (number of deliveries, age at last delivery, age at menopause, and breast feeding). Better and excess nutrition in early and later years of life and fewer births (related to rapid urbanization) may explain in part the increasing incidence of breast carcinoma occurring in Singapore.

Breast cancer risk is positively associated with height

Inter- and intra-national epidemiological studies point to an association between socio-economic status and breast cancer risk. Although there is no direct evidence, the most favoured reason for this relationship is nutritional. An enhanced dietary status, especially during childhood, would be reflected in adult body build. It is, therefore, surprising that there is uncertainty in the literature concerning the association between height and breast cancer risk. In reviewing the publications on this topic it became apparent that case-control studies which found no association between height and risk tended to use self-reported height. In contrast reports claiming a significant, and positive, correlation tended to use heights which were measured by the investigators. In a prospective study we found in a cohort of 2731 ostensibly normal women that, although there was a highly significant linear correlation between self-reported and measured height, the shortest women over-estimated their height whilst the tallest volunteers under-estimated theirs. The significance of crude relative risk and height in this cohort was markedly attenuated when self-reported height was used compared to measured height. Such a systematic error could have a profound effect on the conclusions of studies in this field which relied on self-reporting and could explain the conflicting reports in the literature.

Familial clustering of obesity and breast cancer

One of the most striking characteristics of breast cancer (BC) is a tendency to familial aggregation. In order to evaluate whether familial clustering of obesity could account, at least in part, for the familial aggregation of BC, we compared the adult body size of entire sets of first-degree relatives belonging to 60 families with two or more cases of BC (case families) and 120 BC-free families (control families). Case families included an index case recently admitted for primary BC who had a confirmed first-degree family history for the disease. Control families included one population-based healthy index control with no family history and age-matched (2:1) to index cases. Index cases and controls, recruited from a pool of participants in a large case-control study, completed a questionnaire covering their own body size history as well as that of each of their first-degree relatives (598 case and 1,128 control relatives) using a validated system of body silhouette drawings. The odds ratio (OR) for premenopausal familial BC associated with having one parent markedly obese compared to none was 0.17 (95% confidence interval [CI] 0.04-0.65), while having both parents obese resulted in an OR of 0.25 (95% CI 0.04-1.56). Obesity among siblings was not related to premenopausal familial BC risk nor was familial obesity a significant predictor of familial BC after menopause. Index cases from both menopausal groups tended to be thinner than their unaffected relatives at age 40 years and thereafter. The inverse relationship between parental obesity and premenopausal BC risk is concordant with the protective effect of obesity on early-onset BC previously reported at the individual level.

Timing of weight gain and breast cancer risk

BACKGROUND

Obesity and body-fat distribution have been associated with the incidence of breast and endometrial cancers. It may be critical to determine if the timing of weight gain during periods of hormonal change, such as menarche, pregnancy, or menopause, has different biologic effects, especially secondary to differences in the localization of body fat during these periods. The objective of the current study was to determine if excess weight in any particular decade of life or the timing of weight gain was more significant relative to breast cancer risk.

METHODS

Anthropometric, medical, and hormonal histories were obtained from 218 consecutively recruited, newly diagnosed patients with breast cancer admitted to the H. Lee Moffitt Cancer Center and Research Institute (Tampa, FL) and 436 control subjects, matched in a two to one ratio for age and menopausal status.

RESULTS

A weight gain of 15 pounds or more was observed for 63.8% of the patients compared with 49.3% control subjects (P = 0.0006) from age 30 to current age. Similarly, more than 48% of cases gained more than 15 pounds from ages 16 to 30 compared with 37% (P = 0.01) of the control population. Although weight gain from age 16 to adulthood was significantly higher in patients with breast cancer at each decade when compared with control subjects, a significant and independent association between weight at age 30 (P < 0.0001) and risk of breast cancer was noted.

CONCLUSION

Women who progressively gain weight from puberty to adulthood, and specifically in the third decade of life, should be considered at a higher risk for developing breast cancer.

Wolfe's mammographic patterns in women with gross cystic disease of the breast

The epidemiologic determinants of the mammographic pattern were studied in 710 patients with aspirated gross (> 1 ml) cysts of the breast. The prevalence of the mammograms classified as P2-DY, that are considered to be associated with an increased breast cancer risk, was 636/710 or 89.6%. No relationship between mammographic patterns and characteristics of breast cyst fluid such as K+/Na+ ratio, apocrine changes and dehydroepiandrosterone sulfate concentration was observed. A significant decrease in the proportion of these patterns with increasing age (p = 0.006), Quetelet Index (p < 0.001), parity (p = 0.001), and in postmenopausal women (p = 0.026) was found. Conversely, P2-DY patterns were significantly associated with a later age at menarche (p = 0.023) and alcohol consumption (p = 0.001). In multivariate analysis, an independent association with age was not observed whereas the associations with age at menarche, parity, and relative weight were confirmed. In conclusion, the epidemiologic determinants of mammographic patterns are the same in Gross Cystic Disease patients as in unaffected women, and the lack of correlation between mammographic pattern and cyst type suggests that the latter may represent an independent predictor of breast cancer risk.

Obesity and subcutaneous fat patterning in relation to survival of postmenopausal breast cancer patients participating in the DOM-project

The effect of obesity and fat distribution on survival of breast cancer patients was studied prospectively in 241 women with a natural menopause who participated in a breast cancer screening project, the DOM-project in Utrecht, The Netherlands. Mean follow-up time was 9.1 years and endpoint of interest was death from breast cancer. Fat distribution was assessed by contrasting groups of subscapular and triceps skinfold thickness. No significant differences in survival time between more obese (Quetelet's index > or = 26 kg/m2) and leaner (Quetelet's index < 26 kg/m2) patients or between patients with central fat distribution and patients with peripheral fat distribution were observed. Analyses were stratified by axillary node status, estrogen receptor status, and way of detection (by first screening or afterwards). Results of the stratified analyses were suggestive of a modifying effect of these factors. The absence of an association between obesity and survival time might be explained by two counteracting mechanisms. On the one hand obesity might be related to impaired survival, due to a tumor growth promoting effect of extra-ovarian estrogens. On the other hand obesity might be related to improved survival in a screened population, because obese patients profit more from screening by earlier detection of tumors than leaner counterparts.

Body fat distribution in relation to breast cancer in women participating in the DOM-project

The association between body fat distribution and breast cancer risk was studied in 5923 pre- and 3568 post-menopausal women, participating in a breast cancer screening project (the DOM-project in Utrecht, the Netherlands). Cases were fifty six premenopausal women and thirty eight postmenopausal women with breast cancer detected at screening or afterwards. Controls were women participating in the breast cancer screening project without breast cancer. Waist- and hip circumferences, height and weight were measured at screening, before diagnosis of breast cancer. In postmenopausal women the estimated relative risk of women in the upper tertile of waist/hip ratio compared with women in the lower tertile was 1.89 (95% CI 0.80-4.48), (test for trend p = 0.11). The estimated relative risk of women in the upper tertile of waist circumference compared with women in the lower tertile was 2.86 (95% CI 1.12-7.32), (test for trend p = 0.08). The association between waist circumference and breast cancer was stronger than the association between any of the other anthropometric variables and breast cancer. In premenopausal women the association between fat distribution and breast cancer was equivocal.

A large-scale, hospital-based case-control study of risk factors of breast cancer according to menopausal status

We conducted a large-scale, hospital-based case-control study to evaluate differences and similarities in the risk factors of female breast cancer according to menopausal status. This study is based on a questionnaire survey on life style routinely obtained from outpatients who first visited the Aichi Cancer Center Hospital between January 1, 1988 and December 31, 1992. Among 36,944 outpatients, 1,186 women with breast cancer detected by histological examination were taken as the case group (607 premenopausal women and 445 postmenopausal women) and 23,163 women confirmed to be free of cancer were selected as the control group. New findings and reconfirmed factors of breast cancer were as follows. 1) The risk of at least one breast cancer history among subjects' first-degree relatives was relatively high among pre- as well as post-menopausal women. 2) A protective effect of physical activity against breast cancer was observed among both pre- and post-menopausal women. 3) Dietary control decreased the risk of premenopausal breast cancer. 4) Current smoking and drinking elevated the risk of breast cancer in premenopausal women. 5) Decreasing trends of breast cancer risk were associated with intake of bean curd, green-yellow vegetables, potato or sweet potato, chicken and ham or sausage in premenopausal women, while in postmenopausal women a risk reduction was associated with a more frequent intake of boiled, broiled and/or raw fish (sashimi). Further study will be needed to clarify the age group- and/or birth cohort-specific risk factors for breast cancer among the young generation in Japan.

The relation of body size to plasma levels of estrogens and androgens in premenopausal women (Maryland, United States)

We analyzed data from a cross-sectional study of 107 premenopausal women to evaluate the relations of height, weight, and body mass index (BMI) with plasma hormone levels. Participants were 20- to 40-year old women residing in Maryland (United States), whose reported menstrual cycle lengths were not more than 35 days and whose measured weights for height were 85 to 130 percent of 'desirable' based on 1983 Metropolitan Life Insurance tables. Fasting blood specimens were collected on each of days 5-7, 12-15, and 21-23 of every participant's menstrual cycle and pooled to create follicular, midcycle, and luteal phase samples, respectively, for analysis. Adjusted for age, taller women had significantly higher follicular-phase plasma-estradiol levels (percent difference/cm = 1.5, 95 percent confidence interval [CI] = 0.3-2.7, and heavier women had significantly lower plasma sex-hormone binding globulin (SHBG) levels averaged across the menstrual cycle phases (percent difference/kg = -1.2; CI = -1.9-(-0.6). Body weight within the range studied, however, was not related significantly to the concentration of SHBG-bound estradiol during any phase of the menstrual cycle. The results of this cross-sectional study suggest a possible mechanism by which height may influence breast cancer risk.

A case-control study on breast cancer and body mass. The American Health Foundation--Division of Epidemiology

A hospital-based case-control study was carried out to examine the effect of body weight/fat and physical activity on risk of breast cancer on 617 newly diagnosed breast cancer cases and 531 controls matched to the cases by age (+/- 5 years), race, year of interview (+/- 1 year) and hospital of admission. Breast cancer was not found to be associated with height, while being overweight appeared to be protective in premenopausal women [odds ratio, OR = 0.4 (0.2-0.7) for cases who weighted > or = 72.7 kg versus controls]. Increased body mass index (BMI) was protective in premenopausal women [OR = 0.4 (0.2-0.6) in breast cancer cases with BMI > or = 27 versus controls], but not in postmenopausal women, for whom it was a risk factor [OR = 1.5 (1.0-2.3)]. Few women reported any strenuous physical activity from ages 15 to 22 years (22% of premenopausal, 13% of postmenopausal women), and no significant effect on breast cancer risk was observed.

Anthropometry and breast cancer. Body size--a moving target

Body size is one of the few breast cancer risk factors that can be modified throughout life and therefore should be considered in research on breast cancer prevention. The contrasting effects of body size on premenopausal breast cancer compared with postmenopausal breast cancer and the lack of a strong association between body mass and postmenopausal breast cancer in some cohort studies has led to a view that obesity has little influence on breast cancer risk. These conclusions are based on analyses that consider relative weight at one point in time as an adequate measure of lifelong weight patterns and their metabolic consequences. Recent research suggests that, compared to body mass indices, adult weight gain and increased central body fat may be more specific markers of the metabolic consequences of obesity and therefore may predict health outcomes more consistently. Adult weight gain and increases in central body fat, which commonly occur during menopause, have been associated consistently with an increased risk of postmenopausal breast cancer. The timing of weight gain also appears to influence breast cancer risk; increased relative weight and weight gain after menopause have been associated with the largest increases in relative risks. Overall levels of adiposity, increased central fat deposition, and weight gain are associated with alterations in ovarian hormone and glucose metabolism and in growth factors that may promote breast cancer cell growth. Data on lifelong weight changes and the location of fat depots may more precisely identify women with high risk patterns of sex steroid and glucose metabolism. Similarly, research is needed to determine if weight gain during periods of hormonal change, such as menarche, pregnancy, and menopause, have different biologic effects, perhaps because of differences in the location of fat deposition during these periods. Research also is needed on whether there are critical times relative to breast cancer promotion when excessive weight gain should be avoided. Data are lacking on the influence of weight loss or avoidance of weight gain on breast cancer risk or prognosis.

The association of height, weight, menstrual and reproductive events with breast cancer: results from two prospective studies on the island of Guernsey (United Kingdom)

The association with breast cancer of menstrual and reproductive events, family history of breast cancer, and body size have been studied on two cohorts of 6,706 volunteers on the island of Guernsey (United Kingdom), 168 of whom had breast cancer detected during follow-up. The median follow-up time of the non-cases was 21 years in the first study and 10 years in the second. A time-dependent Cox regression model was fitted to the data with age as the time-dependent variable in order to represent the effect of changing menopausal status. Other variables examined in the model were age at menarche, parity, age at first birth, family history of breast cancer, height, weight (both directly measured), relative weight (weight [kg]/height[m]), and Quetelet's body mass index (weight[kg]/height[m]2). Interactions between age and all other covariates also were examined. Family history was found to be the most important risk factor for women aged less than 51 years (relative risk [RR] = 3.5, 95 percent confidence interval [CI] = 2.0-6.0), and intervals between menarche and first birth longer than 14 years were found to increase significantly the risk of breast cancer in women older than 61 years (RR = 2.4, CI = 1.3-4.4). Height was the only indicator of body size which was associated significantly with risk of breast cancer, the estimated regression coefficient indicating an increase in risk of about 70 percent for women on the 90th centile of height relative to those on the 10th centile. A survey of the literature showed that the association between risk of breast cancer and height was found in those studies which used direct measurements of height but not in others which used self-reported values.

Risk factors for breast cancer by age and menopausal status: a case-control study in Singapore

A case-control study was conducted among Singapore Chinese women, comprised of 200 histologically confirmed cases of breast cancer and 420 hospital controls. Subjects were interviewed on family history of breast cancer, social and demographic characteristics, reproductive history, and diet one year prior to interview. Differences in risk factors were observed according to menopausal status. In the premenopausal group, the most consistently significant nondietary effect was an increased risk with late age at first birth. In postmenopausal women, the most consistent nondietary effects were increased risks with nulliparity, tall stature, high educational status, and a family history of breast cancer. In premenopausal women, the strongest dietary effects were low risks with high intakes of polyunsaturated fatty acids (PUFA), beta-carotene, soya protein as a proportion of all protein, and a high risk with high red-meat intake. No dietary effects were observed in postmenopausal women. Examination of effects by 10-year age groups suggested that the differences in the effects of age at first birth, nulliparity, height, education, beta-carotene intake, and PUFA intake between premenopausal and postmenopausal women were at least partly attributable to age-related differences in the baseline distributions of these variables. The variation in the effects of red meat and soya protein appeared to be attributable mainly to menopausal status itself, which is consistent with the hypothesis that these factors operate on risk by way of hormonal mechanisms.

Body measurements, estrogen availability and the risk of human breast cancer: a case-control study

Recent studies on lifestyle-related mechanisms involved in cardiovascular risk offer important clues for a better understanding of breast-cancer epidemiology. Central body-fat distribution promoted by an affluent dietary intake and a sedentary lifestyle over many years is related to elevated serum triglycerides and free fatty acids, with lower levels of sex-hormone-binding globulin (SHBG). The resulting greater availability of estradiol not bound to SHBG could help to explain the high breast-cancer incidence in Western industrialized countries. We conducted a case-control study comparing 225 women aged 38 to 75 years with operable (stage I or II) breast cancer and 441 women of the same age having no breast cancer who participated in a population-based breast-cancer screening program. Body fatness, as measured by body mass index (BMI), fat distribution as measured by waist-to-hip girth ratio (WHR), body height, serum lipids, SHBG and the available fraction of estradiol were analyzed in a conditional logistic regression, together with family history for breast cancer, reproductive history and smoking. Post-menopausal cases showed no difference in body fatness (BMI), but a significant preponderance of central adiposity (WHR). In contrast, pre-menopausal cases were significantly leaner, but had a similar body-fat distribution as compared with controls. In all women, WHR, and less strongly BMI, was positively correlated with serum levels of triglycerides and available estradiol fractions. An independent, positive linear correlation between body height and relative risk (RR) was observed. Moreover, a significant correlation between SHBG and menarcheal age was seen in cases, but not in controls. These data support our hypothesis that lifestyle relates to breast-cancer risk by metabolic-endocrine mechanisms which modulate the availability of individual sex-steroid concentrations in plasma. The findings of height as a risk factor and adult SHBG levels being correlated with menarcheal age suggest that lifestyle factors promoting breast-cancer development already act around puberty. The leanness of pre-menopausal cases awaits further explanation.

The pattern of risk factors for breast cancer in a southern France population. Interest for a stratified analysis by age at diagnosis

A hospital-based case-control study was conducted over 4 years in Southern France to assess the pattern of established risk factors for breast cancer and to examine its variation according to age at diagnosis. Cases studied (450) were women admitted to the Montpellier Cancer Institute, with histologically confirmed primary breast carcinoma. Controls (576) were patients from a nearby hospital admitted in the early stages of a neurological or mild psychological diseases and from a clinic for general surgery. Any patient with malignant tumours, chronic and cardiovascular diseases were excluded. The total population globally showed the commonly reported pattern for these risk factors. When stratified by age, the reproductive factors occurring early in life (menarche, first full term pregnancy) were shown to be significant risk factors only in the youngest group of patients and do not seem to influence risk in older women, for whom risk factors are those occurring later in life (menopause, obesity). This suggests a complex involvement of the reproductive and sociodemographic features with the various stages of the 'natural history' of breast cancer.

The relationship between body mass and breast cancer among women enrolled in the Cancer and Steroid Hormone Study

We examined the relationship between body mass [weight (kg)/height (m)2] and breast cancer using data from the Cancer and Steroid Hormone Study. The study compared 4323 women aged 20-54 years with newly diagnosed breast cancer identified through population-based tumor registries with 4358 women randomly selected from the general population of the same geographic areas. Among naturally menopausal women, risk of breast cancer increased with increasing body mass index (BMI); those severely overweight (BMI greater than or equal to 32.30) had nearly 3-fold higher risk of breast cancer compared with women in the leanest category (BMI less than 20.00). This positive association appeared stronger with increasing years since menopause and in women who had ever used estrogen replacement therapy. A positive association between body mass and breast cancer risk also was observed among premenopausal women; however, risk estimates were substantially lower. Substantial weight gain from adolescence to adulthood was a more important risk factor than lifelong obesity. Prevalence of obesity increases with age; our results suggest that interventions that prevent this trend could have an important effect on breast cancer risk, especially during the menopausal years.