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.     

Correlates of high-density mammographic parenchymal patterns by menopausal status in a rural population in Northern Greece

Reproductive factors affect breast cancer risk, but less is known of their associations with mammographic density and whether these differ by menopausal status. We report on a cross-sectional study of 1946 pre- and 3047 post-menopausal women who joined a breast screening programme in Northern Greece during 1993-1997. The odds of having a high-density Wolfe pattern (P2/DY) was inversely associated with age (P for linear trend <0.001) in both pre- and post-menopausal women and, for post-menopausal women, with years since menopause (P < 0.001). The odds of a P2/DY pattern declined with higher parity (P < 0.001) and younger age at first pregnancy (P = 0.05) in both pre- and post-menopausal women. They also decreased with the duration of breast-feeding in pre-menopausal women (P = 0.03 in pre- and P = 0.69 in post-menopausal women; test for interaction with menopausal status: P = 0.07). Age at menarche, age at menopause and the number of miscarriages/abortions were not associated with mammographic density. Age at first pregnancy and parity were strong correlates of mammographic density in pre- and post-menopausal women while duration of breast-feeding appeared to be particularly important in pre-menopausal women.     

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.     

Reproductive factors, hormone use and the risk of lung cancer among middle-aged never-smoking Japanese women: a large-scale population-based cohort study

Although a link between female hormonal factors and the risk of lung cancer has been suggested, few studies have examined this association in detail. We investigated the associations between reproductive factors, hormone use and the risk of lung cancer in a population-based prospective study. Self-administered questionnaires were distributed to 44,677 lifelong never-smoking women in 1990-1994 to assess menstrual and reproductive factors and hormone use. After 8-12 years of follow-up, 153 lung cancer cases were diagnosed. Relative risk (RR) and 95% confidence intervals (CI) were calculated using the Cox proportional hazards model. Age at menopause, age at menarche, number of children, age at first live birth, breast feeding and use of hormones were not associated with a risk of lung cancer, either overall or among postmenopausal women or women with natural menopause. Compared to women with both late age at menarche (> or =16) and early age at menopause (< or =50), those with either early age at menarche or late age at menopause had a >2-fold, significant increase in the risk of lung cancer. Induced menopausal women with experience of hormone replacement therapy had a significantly elevated risk compared to naturally menopausal women without female hormone use, with an RR of 2.40 (95% CI 1.07-5.40). These findings suggest that both endogenous and extraneous estrogen may be involved in the etiology of lung cancer.     

The association between lactation and breast cancer in an international case-control study: A re-analysis by menopausal status

In the large, hospital-based, international case-control study of breast cancer conducted by MacMahon and colleagues in the 1960s, no protective effect of lactation was observed. However, more recent reports have suggested that such an association may be limited to pre-menopausal women. Therefore, a re-analysis of the data from that original study was performed by menopausal status and with control for additional breast-cancer risk factors since identified. Overall, data from 4,671 parous pre-menopausal and 7,200 parous post-menopausal women were analyzed, from 7 different sites representing areas of high risk (Glamorgan, Wales; Boston, USA), moderate risk (Athens, Greece; Slovenia, ex-Yugoslavia; São Paolo, Brazil), and low risk (Tokyo, Japan; Taipei, Taiwan) of breast cancer. No significant effect of lactation was found for pre-menopausal or post-menopausal women from the high-, moderate-, or low-risk areas; the center-adjusted, combined odds ratio (OR) for having breast-fed was 1.05 (95% confidence interval, 0.86–1.29) among pre-menopausal and 1.04 (0.88–1.24) among post-menopausal women. Moreover, examination of cumulative duration of lactation did not support an inverse association between breast cancer and increased length of total breast-feeding. In conclusion, re-analysis of these data, by menopausal status and adjusting for age at first parity, age at menarche, age at menopause, body-mass index and years of schooling, did not reveal a protective effect of lactation or duration of lactation against breast-cancer occurrence among the pre-menopausal, parous women. Int. J. Cancer 71:166–169, 1997. © 1997 Wiley-Liss, Inc.     

The role of age at menarche and at menopause on breast cancer risk: combined evidence from four case-control studies.

The role of age at menarche and at menopause on breast cancer risk was reassessed in a combined analysis of four Italian case-control studies including a total of 6,075 cases and 5,492 controls. The risk of breast cancer was lower in women whose menarche occurred at age 15 or over, but there was no evidence for the risk to increase with decreasing age at menarche below age 15. Compared with women with earlier menarche, the relative risk (RR) was 0.9 (95% confidence interval, CI 0.7-1.0) for those with menarche at age 15, 0.8 (95% CI 0.6-0.9) for menarche at 16, and 0.7 (95% CI 0.5-0.8) for menarche at age 17 or over. There was no significant interaction between age at menarche and study centre or age at diagnosis, parity and age at first birth. In relation to age at menopause, compared with women whose menopause occurred at age 40 or less, the relative risk was 1.1 (95% CI 0.8-1.3) between 40 and 44, 1.2 (95% CI 0.9-1.4) between 45 and 49, 1.4 (95% CI 1.2-1.8) between 50 and 53, and 1.4 (95% CI 1.1-1.8) above 53. The risk estimates were comparable in various studies, and the trend in risk with age at menopause was statistically significant. The risk estimates tended to be somewhat higher at peri-menopausal age (45 to 54 years), but no consistent pattern was evident across subsequent strata of age, and the interaction with age was not significant. Likewise, no consistent interaction was observed with parity, age at first birth or body mass index.(ABSTRACT TRUNCATED AT 250 WORDS)     

Body mass index and colon cancer risk in Chinese people: menopause as an effect modifier

High body mass index (BMI) has consistently been associated with increased colon cancer risk in men, but not in women. It is hypothesised that menopause-related changes in oestrogen levels play a role in gender-specific risk patterns. Most studies have been conducted in Western countries, where high incidence rates are coupled with a high prevalence of obesity and relatively common use of hormone replacement therapy (HRT) in post-menopausal women. This study evaluated the correlation between body mass index (BMI) and colon cancer risk in a relatively lean population, comprising 931 cases and 1552 controls, in Shanghai, China, where HRT use was extremely rare among women, during 1990-1993. Among men, colon cancer risk significantly increased with increasing BMI (P-trend=0.005). Among women, the risk varied with age and menopause status in a similar pattern. Within each menopause stratum, however, the BMI-related risk was similar for those aged under 55 years and those aged 55 years and over, indicating a menopause rather than age effect. Among pre-menopausal women, the odds ratios (ORs) for subjects in the highest versus lowest quintile were 1.9 (95% CI 1.1-4.9) for those under 55 years of age, and 2.2 (95% CI 1.4-8.2) for those aged 55 years and over. Among post-menopausal women, the corresponding ORs were 0.6 (95% CI 0.5-0.91) and 0.7 (95% CI 0.5-0.95), respectively. Our findings suggest that BMI predicts colon cancer risk in both genders. Among women, however, the risk is modified by menopause status, possibly through altered endogenous oestrogen levels.     

Anthropometric variables and risk of breast cancer

The role of anthropometric variables in the risk of breast cancer has been investigated using pooled data from 2 hospital-based case-control studies conducted in Italy for a total data-set of 3,247 cases and 3,263 controls. No association was observed in pre-menopausal women between breast cancer risk and height, weight, indices of body mass (W/H2; W/H1.5) and surface area. In post-menopausal women, the risk of breast cancer was inversely related to height, being 0.8 in taller women (greater than 165 cm) compared with women 155 cm tall or less; the trend in risk, although not constantly decreasing, was statistically significant (p trend = 0.03). A direct, statistically significant association emerged with weight and indices of body mass and post-menopausal breast cancer risk. Considering 2 indices of body weight (W/H2 and W/H1.5) and relative to thinner women, the respective estimated risks of post-menopausal breast cancer increased to 1.4 and 1.3 for grossly obese women, and the corresponding p values for trend were respectively 0.002 and 0.02. The role of overweight was more evident in women with early age at menopause, thus suggesting a duration-risk effect.     

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.     

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.     

Role and impact of menstrual and reproductive factors on breast cancer risk in Japan.

The aim of this study was to clarify the role and impact of menstrual and reproductive factors in relation to breast cancer and its hormone receptor-defined subtype, overall and separately among premenopausal and postmenopausal women in a low-risk population, using data from the Japan Public Health Center-based Prospective study. A total of 55 537 women aged 40-69 years completed a self-administered questionnaire, which included items about menstrual and reproductive history. During 1990-2002, 441 newly diagnosed cases of breast cancer were identified. Early age at menarche for premenopausal women, late age at natural menopause, nulliparity and low parity for both premenopausal and postmenopausal women, and late age at first birth for postmenopausal women were significantly associated with an increased risk of breast cancer. No overall significant associations were seen between the use of exogenous female hormones or breast feeding and breast cancer risk. Age at menarche and age at natural menopause were somewhat more closely associated with the risk of progesterone receptor-negative than positive breast cancer although no difference was observed for estrogen receptor status. Risks associated with parity, number of births and age at first birth did not significantly differ by hormone receptor-defined breast cancer. Our findings suggest that menstrual and reproductive factors may play an important role in the development of breast cancer among low-risk populations, similarly as they do in Western populations, and that risk factors might differ by hormone receptor status.     

Age at menarche and menopause and breast cancer risk in the International BRCA1/2 Carrier Cohort Study.

BACKGROUND: Early menarche and late menopause are important risk factors for breast cancer, but their effects on breast cancer risk in BRCA1 and BRCA2 carriers are unknown. METHODS: We assessed breast cancer risk in a large series of 1,187 BRCA1 and 414 BRCA2 carriers from the International BRCA1/2 Carrier Cohort Study. Rate ratios were estimated using a weighted Cox-regression approach. RESULTS: Breast cancer risk was not significantly related to age at menopause [hazard ratio [HR] for menopause below age 35 years, 0.60 [95% confidence interval (95% CI), 0.25-1.44]; 35 to 40 years, 1.15 [0.65-2.04]; 45 to 54 years, 1.02 [0.65-1.60]; >or=55 years, 1.12 [0.12-5.02], as compared with premenopausal women]. However, there was some suggestion of a reduction in risk after menopause in BRCA2 carriers. There was some evidence of a protective effect of oophorectomy (HR, 0.56; 95% CI, 0.29-1.09) and a significant trend of decreasing risk with increasing time since oophorectomy, but no apparent effect of natural menopause. There was no association between age at menarche and breast cancer risk, nor any apparent association with the estimated total duration of breast mitotic activity. CONCLUSIONS: These results are consistent with other observations suggesting a protective effect of oophorectomy, similar in relative effect to that in the general population. The absence of an effect of age at natural menopause is, however, not consistent with findings in the general population and may reflect the different natural history of the disease in carriers.     

Influence of non-contraceptive exogenous and endogenous sex hormones on breast cancer risk in Denmark

In order to evaluate the influence of sex hormones on breast cancer risk, a population-based case-control study was conducted in Denmark, including 1,486 cases diagnosed over a one-year period. These were identified from the files of the nation-wide clinical trial of the Danish Breast Cancer Cooperative Group and the Danish Cancer Registry. The control group was an age-stratified random sample of 1,336 women from the general population. Data on risk factors were collected by self-administered (mailed) questionnaires. The major findings included a trend (p = 0.001) toward decreasing risk with increasing age at menarche in pre-menopausal women, trends toward increasing risk with continued menstrual cycles after the age of 50 in pre- and post-menopausal women (p-values of 0.01 and 0.002 respectively), and a trend (p = 0.002) toward increasing risk with increasing duration of non-contraceptive sex hormone usage in post-menopausal women. Information on brand names made it possible to examine types of hormones used, which showed an RR of 1.36 (95% CI 0.98-1.87) for sequential therapy with oestrogen and progestagen and RR = 2.31 (95% CI 1.37-3.88) for combined oestrogen-androgen treatment. These results should be interpreted with caution, however, needing verification from other studies. No significant association was observed between breast cancer and self-reported height and weight.     

Lactation and the risk of breast cancer

Some factors are suggested to have an association with an increased risk of breast cancer, which are called risk factors. Lactation is one of the risk factors that still needs to be studied because of conflicting findings in epidemiological studies and also uncertainty regarding biologic plausibility. Our objective was to study the relationship between lactation and the risk of breast cancer. A pair of unmatched case control studies was held among parous women at Dr. Soetomo Hospital (general hospital) and some private hospitals in the Surabaya municipality. There are 219 (51.9%) cases and 203 (48.1%) controls analyzed in this study. Age, age at menarche, regular menstruation and number of parity between both groups are not statistical different. When we divided the age at menarche (below 13), it was statistically different. The cases consisted of more women with menarche below 13 (p = 0.00038). Other factors showing statistical differences in the risk of breast cancer between case and control are age at first delivery, family history of breast cancer and age at menopause. Women who have lactated (more than 4-month duration of breast feeding) show a "protective effect" against breast cancer, OR 0.57 (95% CI 0.33-0.99). However, there was no clear duration of lactation and the risk of breast cancer. Logistic regression analysis showed that lactation was not any independent factor. Lactation exerts a "protective effect" against breast cancer. However, the duration of lactation did not show an influence in reducing the risk of breast cancer, and logistic regression analysis did not show that lactation was an independent factor in the risk of breast cancer.     

Differential effects of reproductive factors on the risk of pre- and postmenopausal breast cancer. Results from a large cohort of French women

The aim of this study was to obtain a better understanding of the role of hormonal factors in breast cancer risk and to determine whether the effect of reproductive events differs according to age at diagnosis. It analysed the effect of age at menarche, age at first full-term pregnancy, number of full-term pregnancies and number of spontaneous abortions both on the overall risk of breast cancer and on its pre- or postmenopausal onset, using the data on 1718 breast cancer cases, obtained from a large sample of around 100000 French women participating in the E3N cohort study. The results provide further evidence that the overall risk of breast cancer increases with decreasing age at menarche, increasing age at first pregnancy and low parity. No overall effect of spontaneous abortions was observed. The effect of these reproductive factors differed according to menopausal status. Age at menarche had an effect on premenopausal breast cancer risk, with a decrease in risk with increasing age of 7% per year (P<0.05). Compared to those who had their first menstrual periods at 11 or before, women experiencing menarche at 15 or after had an RR of 0.66 (95% CI 0.45-0.97) in the premenopausal group. Age at first full-term pregnancy had an effect on both pre- and postmenopausal breast cancer risk, with significant tests showing increasing risk per year of increasing age (P=0.001 and P<0.05 respectively). A first full-term pregnancy above age 30 conveyed a risk of 1.63 (95% CI 1.12-2.38) and 1.35 (95% CI 1.02-1.78) in the pre- and postmenopausal groups respectively. A protective effect of high parity was observed only for postmenopausal breast cancer risk (P for trend test =0.001), with point estimates of 0.79 (95% CI 0.60-1.04), 0.69 (95% CI 0.54-0.88), 0.66 (95% CI 0.51-0.85) and 0.64 (95% CI 0.48-0.86) associated to a one, two, three and four or more full-term pregnancies. A history of spontaneous abortion had no significant effect on the risk of breast cancer diagnosed before or after menopause. Our results suggest that reproductive events have complex effects on the risk of breast cancer.     

Body mass and stage of breast cancer at diagnosis

Obesity is a well-known risk factor for postmenopausal breast cancer. In contrast, the relationship between obesity and stage of breast cancer at diagnosis is less clear. We hypothesized that increased breast size in obese women may delay discovery of breast tumors. Thus, the purpose of our study was to examine whether there is an association between body mass and stage of breast cancer at diagnosis using hospital medical records. Newly diagnosed breast cancer cases (n = 966) in the Baltimore metropolitan area from 1991 to 1997 were included in our study. Patient information including age, ethnicity, weight, height and pathology data were obtained from hospital medical records. High body mass was significantly associated with late stage of breast cancer at diagnosis. Women who were obese (body mass index [BMI] > or = 27.3) were more likely to be at an advanced stage at diagnosis compared with women with a BMI of < 27.3 (multivariate-adjusted odds ratio [OR] 1.57, 95% confidence interval [CI] 1.15-2.14). The association between body mass and stage at diagnosis was stronger among women younger than 50 years (OR 2.34, 95% CI 1.34-4.08) compared with women 50 years or older (OR 1.30, 95% CI 0.89-1.91). Our study suggests that higher body mass is associated with advanced stage of breast cancer at diagnosis. This finding may be of considerable concern, given the increasing prevalence of obesity in women in the United States and the poor prognosis associated with late-stage tumors.     

Prevalence of Known Risk Factors in Women Diagnosed with Breast Cancer at Inmol Hospital,Lahore, Punjab

Background: Breast cancer is the most prevalent cancer in women worldwide and its frequency is increasing gradually in many countries. Over the last three decades an increase in the breast cancer has been witnessed in the earlier low-risk Asian countries including Pakistan. Purpose: The objective of the current study was to assess the prevalence of known risk factors like early menarche, late menopause, socio economic, reproductive and demographic factors, among women diagnosed with breast cancer at INMOL hospital, Lahore, Punjab, as little information exists in this regard. Materials and Methods: A survey study was conducted on 200 women diagnosed with breast cancer who were seen at Institute of Nuclear Medicine and Oncology (INMOL) hospital, Lahore. A structured questionnaire was administered to these patients regarding the known risk factors through face to face interviews after obtaining appropriate consent. Results: Regarding non-modifiable risk factors, our study showed that majority of the breast cancer patients were diagnosed at 35-45 years (32.5%) or at older age (≤46) and experienced menarche at 12 years or older (66 %). Likewise, a large number of patients reached menopause at the age of 45 years (60%), had no family and personal history of breast cancer (80%) and hence fell in a low risk category. Regarding modifiable risk factors in women diagnosed with breast cancer, most of the patients fell in low risk strata as the majority were married (98%) at young age, breastfed their children for 12 months or more (88%) and bore two to three children (80%). Considering income criteria, the majority of the patients had a low risk profile as they belonged to middle class (70%), urban area (60%) and were house wives (80%). However, it was noted that a considerable number of women (34%) diagnosed with breast cancer experienced menarche at an early age (<12) and reached menopause after the age of 45 years. This situation is further augmented by environmental changes and dietary habits and places them in a high risk category.     

Association of menstrual and reproductive factors with breast cancer risk: results from the Shanghai Breast Cancer Study

The incidence of breast cancer among women in Shanghai, a traditionally low-risk population, has increased substantially over the past 20 years. To evaluate the association of menstrual and reproductive factors with breast cancer risk and the influence of these factors on the temporal trend of breast cancer incidence, we analyzed data from the Shanghai Breast Cancer Study, a population-based case-control study of breast cancer recently completed among Chinese women in urban Shanghai. In-person interviews were completed for 1,459 women newly diagnosed with breast cancer between ages 25 and 64 and for 1,556 controls frequency-matched to cases by age. Unconditional logistic regression was employed to estimate adjusted odds ratios (ORs) and 95% confidence intervals (CIs) related to menstrual and reproductive factors. Earlier menarcheal age, nulliparity, and later age at first live birth were associated with increased risk of breast cancer among both pre- and post-menopausal women, while never having breast-fed and later age at menopause were associated with elevated risk only among post-menopausal women. Among controls, 32% of younger women (40 years) reported starting menarche at age of 13 or younger, and this factor contributed to 44% of cases diagnosed among younger women and 26% to 28% of cases in older women. Older age at first live birth or at menopause explained a considerable portion of cases diagnosed in older, but not younger, women. Our study suggests that the changes in menstrual and reproductive patterns among women in Shanghai have contributed to the recent increase in breast cancer incidence, particularly among younger women.     

Impact of established risk factors for breast cancer in nulligravid Japanese women

BACKGROUND: The mechanism by which pregnancy impacts breast cancer risk remains poorly understood. There is a need for detailed quantification of risk in nulliparous women. We therefore have undertaken a case-referent study of breast cancer employing data from the Hospital-based Epidemiologic Research Program at Aichi Cancer Center (HERPACC), Japan, examining the impact of reproductive and anthropometric factors on breast cancer risk among nulligravid women compared with their parous counterparts. METHODS: In total, 2032 breast cancer cases were included, and 17848 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. RESULTS: A protective effect of later age at menarche was observed among parous women, but it did not alter risk in nulligravid cases. The risk increment with a family history appeared to be most pronounced among premenopausal cases with no history of pregnancy (OR=2.68, 95% CI: 1.41-5.11). Among postmenopausal women, positive associations with height and current body mass index (BMI) in the nulligravid group were similar to those observed in the parous group. The present study indicated that age at menopause, family history in premenopausal women, and height and obesity in postmenopausal women seemed to exert more influence in nulligravid women. Formal tests for interaction between maternity status and these factors, however, did not prove statistically significant. CONCLUSION: Our findings suggest that established risk factors for breast cancer have an additive impact with nulligravid status. Thus, it is implied that obesity control for all women, including nulliparous individuals, is important from a practical viewpoint for primary breast cancer prevention.     

Risk factors for renal-cell carcinoma in Denmark. III. Role of weight,physical activity and reproductive factors

A population-based case-control study of risk factors for renal-cell carcinoma was conducted in Denmark from 1989 to 1992. A total of 368 histologically verified cases and 396 controls were included. Information on weight, height, physical activity and reproductive factors were collected in a structured interview, along with information on other suspected risk factors. A significant increase in risk was seen for obese women but not obese men. Although there was no clear gradient, the risk was highest among women with a relative weight in the upper 5% (OR 6.1; 95% CI, 2.3 to 16.1). The increased risk was most evident for high relative weight in ages 30 to 50. No association was observed for height or physical activity. Use of amphetamines was associated with increased risk but, because of the close link with obesity, we were unable to provide evidence that amphetamines are an independent risk factor. We found some evidence for an association with reproductive variables, including decreased risk for women with late menarche and first pregnancy and birth. We observed no association with number of pregnancies or age at menopause, or use of estrogen-containing medication. © 1994 Wiley-Liss, Inc.