Effect of family history,obesity and exercise on breast cancer risk among postmenopausal women

We examined effects of obesity and lifetime exercise patterns on postmenopausal breast cancer risk according to family history in a large population-based case control study conducted in Los Angeles County, California, because we hypothesized that both factors would affect risk through similar mechanistic pathways, and that their effects would be stronger among women with a family history. We studied 1883 postmenopausal breast cancer case subjects and 1628 postmenopausal control subjects ranging in age from 55-72 years. Cases were diagnosed with incident breast cancer in the late 1980s and 1990s. Controls were individually matched to case subjects on age, ethnic origin and neighborhood. In-person interviews determined known breast cancer risk factors including: height, weight, lifetime exercise, and family history of breast and other cancers. Breast cancer risk was raised among women who had at least 1 first-degree relative with breast cancer (odds ratio [OR] = 1.68; 95% confidence interval [CI] = 1.36-2.08). Risk increased with increasing levels of body-mass index (wt-kg/ht-m(2)) (p-trend = 0.005). Breast cancer risk was reduced among women who maintained, on average, 17.6 metabolic equivalent of energy expenditure (MET)-hr of activity/week from menarche onward (OR = 0.66; 95% CI = 0.48-0.90). Body-mass index, adjusted for lifetime exercise, was strongly associated with breast cancer risk among women with a positive family history of breast cancer (p-trend < 0.0001), but only weakly associated among women with no family history (p-trend = 0.08; homogeneity of trends p = 0.0005). In contrast, the risk reduction associated with exercise activity, adjusting for body-mass index, was limited to women without a family history of breast cancer (p-trend = 0.001; homogeneity of trends p = 0.005). Body-mass index and exercise activity, both modifiable risk factors for breast cancer, seem to have differential effects depending on a woman's family history of breast cancer, and may impact risk through different biological mechanisms.     

Influence of prediagnostic recreational physical activity on survival from breast cancer

Recreational physical activity (RPA) is associated with a reduced risk of developing breast cancer, but there is limited research on whether prediagnostic RPA influences survival after breast cancer diagnosis or not. We evaluated the association between prediagnostic RPA and risk of death in 1508 women with a first breast cancer diagnosis during 1996 and 1997 in the population-based Long Island Breast Cancer Study Project. A 5-year mortality, through the end of 2002, was assessed using the National Death Index (N=196). An in-person interview was completed shortly after diagnosis to obtain information on lifetime RPA, which was expressed as metabolic equivalent task hours per week (MET-h/week). A lower risk of all-cause death was observed for women who engaged in an average of 9 or more MET-h/week of RPA from menarche to diagnosis compared with women who did not exercise [age-adjusted and BMI adjusted hazard ratio (HR)=0.57; 95% confidence interval (CI)=0.39-0.83], an association that was similar when evaluated according to menopausal status. Compared with women who did not engage in moderate RPA, those who engaged in any moderate intensity lifetime RPA (>0 MET-h/week) were found to have lower all-cause mortality (HR=0.62; 95% CI=0.46-0.84) and breast cancer-specific mortality (HR=0.64; 95% CI=0.43-0.93). Among postmenopausal women, RPA that took place after menopause resulted in a decrease in overall mortality, whereas no association was observed for RPA which took place prior to menopause (for >0 MET-h/week of RPA vs. no RPA, the HR=0.61; 95% CI=0.39-0.94 and HR=1.00; 95% CI=0.65-1.54, respectively). This study provides support that RPA prior to breast cancer diagnosis improves survival.     

Leisure-time physical activity in relation to breast cancer among young women (Washington, United States)

It has been hypothesized that women who participate in vigorous physical activity may have lower risk of breast cancer due to lower lifetime exposure to ovarian hormones. A population-based case-control study was conducted to investigate the association between leisure-time physical activity and risk of breast cancer among women aged 21 to 45 years. Cases were 747 women diagnosed with invasive breast cancer between 1983 and 1990 in three counties of western Washington state (United States), and were identified through the Seattle-Puget Sound Surveillance, Epidemiology, and End Results (SEER) registry. Controls were 961 women selected from the same area by random-digit telephone dialing. Physical activity was assessed through personal interview, with questions on frequency and duration of each type of recreational activity during the two-year period immediately prior to reference date (date of diagnosis for cases and a comparable assigned date for controls) and between ages 12 and 21. For the two-year time period before diagnosis, there was no association with frequency of activity (age-adjusted odds ratio [OR]=0.93, 95 percent confidence interval [CI]=0.71-1.22 for four or more episodes per week cf none), total hours spent in physical activity (age-adjusted OR=0.92, CI=0.71-1.22 for four or more hours per week cf none) or MET (metabolic equivalent energy expenditure unit) (age-adjusted OR=0.95, CI=0.73-1.23 for 18 or more METs per week cf none), nor any trend in risk with increasing activity levels. Similarly, there was no association between leisure activity during adolescence and breast cancer risk. These results were not confounded further by body mass index (wt/ht2), age at menarche, age at first full-term pregnancy, parity, family history of breast cancer, or other measured health behaviors. Our findings do not support a protective effect of leisure-time physical activity either in the adolescent years or in adulthood on breast cancer in young women.     

Physical exercise reduces risk of breast cancer in Japanese women

To evaluate the effects of physical exercise on breast cancer risk, a large-scale case-referent study of 2376 incident breast cancer cases and 18 977 non-cancer referents was conducted using data from the hospital-based epidemiologic research program at Aichi Cancer Center (HERPACC). To adjust appropriately for possible confounders, we examined the effects within subgroups of the study population. The multivariable-adjusted odds ratio (OR) was 0.81 (95% confidence interval (CI): 0.69–0.94) for twice a week or more regular exercise. We observed a decreased risk of breast cancer for women who regularly exercised for health twice a week or more, irrespective of menopausal status, and were able to detect greater risk reductions within particular subgroups, including women who were parous, without a family history or non-drinkers. Among premenopausal women, a particularly strong protective effect of physical exercise was observed (OR=0.57, 95%CI: 0.28–1.15) for those women whose body mass index (BMI) was high (BMI≥25). In contrast, risk reduction was found (OR=0.71, 95%CI: 0.50–1.01) among postmenopausal women whose BMI was medium (BMI: 22–25). Stratification of history of stomach cancer screening to adjust modifying effects of healthy consciousness allows a more precise assessment of the protective effect of exercise twice a week or more, independent of stomach cancer screening history. This study provides evidence that physical exercise, especially exercise twice a week or more, reduces the risk of breast cancer among Japanese women. (Cancer Sci 2003; 94: 193–199)     

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.     

Body size in early life and breast cancer risk in African American and European American women

Purpose

There is growing evidence that body size in early life influences lifetime breast cancer risk, but little is known for African American (AA) women.

Methods

We evaluated body size during childhood and young adulthood and breast cancer risk among 1,751 cases [979 AA and 772 European American (EA)] and 1,673 controls (958 AA and 715 EA) in the Women’s Circle of Health Study. Odds ratio (OR) and 95 % confidence intervals (CI) were computed using logistic regression models while adjusting for potential covariates.

Results

Among AA women, being shorter at 7–8 years compared to peers was associated with increased postmenopausal breast cancer risk (OR 1.68, 95 % CI 1.02–2.74), and being heavier at menarche with decreased postmenopausal breast cancer risk, although of borderline significance (OR 0.45, 95 % CI 0.20–1.02). For EA women, being shorter from childhood through adolescence, particularly at menarche, was associated with reduced premenopausal breast cancer risk (OR 0.55, 95 % CI 0.31–0.98). After excluding hormone replacement therapy users, an inverse association with postmenopausal breast cancer was found among EA women reporting to be heavier than their peers at menarche (OR 0.18, 95 % CI 0.04–0.79). The inverse relationship between BMI at age 20 and breast cancer risk was stronger and only statistically significant in EA women. No clear association with weight gain since age 20 was found.

Conclusions

Findings suggest that the impact of childhood height on breast cancer risk may differ for EA and AA women and confirm the inverse association previously reported in EA populations with adolescent body fatness, in AA women.     

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.     

Lifetime physical activity and breast cancer risk in the Shanghai Breast Cancer Study

Overall physical activity in adolescence and adulthood, and changes in activity over the lifespan were analysed by in-person interviews among 1459 women newly diagnosed with breast cancer and 1556 age-matched controls in urban Shanghai. Physical activity from exercise and sports, household, and transportation (walking and cycling) was assessed in adolescence (13-19 y) and adulthood (last 10 y), as was lifetime occupational activity. Logistic regression was used to estimate odds ratios (OR) and 95% confidence limits (OR (95% CL)) while controlling for confounders. Risk was reduced for exercise only in adolescence (OR = 0.84 (0.70-1.00)); exercise only in adulthood (OR = 0.68 (0.53-0.88)), and was further reduced for exercise in both adolescence and adulthood (OR = 0.47 (0.36-0.62)). Graded reductions in risk were noted with increasing years of exercise participation (OR(1-5 yrs)= 0.81 (0.67-0.94); OR(6-10 yrs)= 0.74 (0.59-0.93); OR(11-15 yrs)= 0.55 (0.38-0.79); OR(16 + yrs)= 0.40 (0.27-0.60);P(trend,)< 0.01). Lifetime occupational activity also was inversely related to risk (P(trend)< 0.01). These findings demonstrate that consistently high activity levels throughout life reduce breast cancer risk. Furthermore, they suggest that women may reduce their risk by increasing their activity levels in adulthood.     

克拉玛依市区女性乳腺癌危险因素的病例对照研究

 目的　探讨克拉玛依市区女性乳腺癌的危险因素。方法　用病例对照研究方法调查129例女性乳腺癌和对应的129名对照者,用Logistic回归模型进行乳腺癌危险因素分析。结果　乳腺癌的危险因素有乳腺癌家族史（OR＝2.744,95 % CI＝1.884～4.674）、乳腺增生症（OR＝1.423,95 % CI＝1.160～1.810）、 乳腺炎（OR＝2.363,95 % CI＝2.039～3.934）、子宫肌瘤（OR＝1.623,95 % CI＝1.263～2.024）、 流产（OR＝1.723,95 % CI＝1.143～2.600）、 饮酒（OR＝1.243,95 % CI＝1.040～1.483）、精神创伤（OR＝2.184,95 % CI＝1.753～3.025）、长期接触电离辐射（OR＝1.374,95 % CI＝1.152～1.699）; 保护因素有初潮年龄增大（OR＝0.773,95 % CI＝0.674～0.956）、累计哺乳时间（OR＝0.672,95 % CI＝0.480～0.941）、坚持运动（OR＝0.572,95 % CI＝0.391～0.837）。结论　以上11个因素为克拉玛依市区女性乳腺癌重要的危险因素和保护因素。     

Adult weight gain, fat distribution and mammographic density in Spanish pre- and post-menopausal women (DDM-Spain)

High mammographic density (MD) is a phenotype risk marker for breast cancer. Body mass index (BMI) is inversely associated with MD, with the breast being a fat storage site. We investigated the influence of abdominal fat distribution and adult weight gain on MD, taking age, BMI and other confounders into account. Because visceral adiposity and BMI are associated with breast cancer only after menopause, differences in pre- and post-menopausal women were also explored. We recruited 3,584 women aged 45-68 years within the Spanish breast cancer screening network. Demographic, reproductive, family and personal history data were collected by purpose-trained staff, who measured current weight, height, waist and hip circumferences under the same protocol and with the same tools. MD was assessed in the left craniocaudal view using Boyd's Semiquantitative Scale. Association between waist-to-hip ratio, adult weight gain (difference between current weight and self-reported weight at 18 years) and MD was quantified by ordinal logistic regression, with random center-specific intercepts. Models were adjusted for age, BMI, breast size, time since menopause, parity, family history of breast cancer and hormonal replacement therapy use. Natural splines were used to describe the shape of the relationship between these two variables and MD. Waist-to-hip ratio was inversely associated with MD, and the effect was more pronounced in pre-menopausal (OR = 0.53 per 0.1 units; 95 % CI = 0.42-0.66) than in post-menopausal women (OR = 0.73; 95 % CI = 0.65-0.82) (P of heterogeneity = 0.010). In contrast, adult weight gain displayed a positive association with MD, which was similar in both groups (OR = 1.17 per 6 kg; 95 % CI = 1.11-1.23). Women who had gained more than 24 kg displayed higher MD (OR = 2.05; 95 % CI = 1.53-2.73). MD was also evaluated using Wolfe's and Tabár's classifications, with similar results being obtained. Once BMI, fat distribution and other confounders were considered, our results showed a clear dose-response gradient between the number of kg gained during adulthood and the proportion of dense tissue in the breast.     

Associations between anthropometric characteristics,physical activity,and breast cancer risk in a Canadian cohort

Obesity, physical inactivity, and sedentary behavior, concomitants of the modern environment, are potentially modifiable breast cancer risk factors. This study investigated the association of anthropometric measurements, physical activity and sedentary behavior, with the risk of incident, invasive breast cancer using a prospective cohort of women enrolled in the Canadian Study of Diet, Lifestyle and Health. Using a case-cohort design, an age-stratified subcohort of 3,320 women was created from 39,532 female participants who returned completed self-administered lifestyle and dietary questionnaires at baseline. A total of 1,097 incident breast cancer cases were identified from the entire cohort via linkage to the Canadian Cancer Registry. Cox regression models, modified to account for the case-cohort design, were used to estimate hazard ratios (HR) and 95 % confidence intervals (CI) for the association between anthropometric characteristics, physical activity, and the risk of breast cancer. Weight gain as an adult was positively associated with risk of post-menopausal breast cancer, with a 6 % increase in risk for every 5 kg gained since age 20 (HR 1.06; 95 % CI 1.01–1.11). Women who exercised more than 30.9 metabolic equivalent task (MET) hours per week had a 21 % decreased risk of breast cancer compared to women who exercised less than 3 MET hours per week (HR  0.79; 95 % CI 0.62–1.00), most evident in pre-menopausal women (HR  0.62; 95 % CI 0.43–0.90). As obesity reaches epidemic proportions and sedentary lifestyles have become more prevalent in modern populations, programs targeting adult weight gain and promoting physical activity may be beneficial with respect to reducing breast cancer morbidity.     

Physical activity and breast cancer risk in women aged 20-54 years

BACKGROUND/METHODS: Although several studies have suggested that physical activity is associated with a decreased risk of breast cancer, such a decrease has not been found consistently, perhaps because physical activity was assessed in different ways and for restricted periods. Few studies have assessed the risk of breast cancer in relation to lifetime physical activity. We used data from a population-based, case-control study, including 918 case subjects (aged 20-54 years) and 918 age-matched population control subjects, to examine associations between breast cancer risk and physical activity at ages 10-12 years and 13-15 years, lifetime recreational activity, and title of longest held job. RESULTS: Women who were more active than their peers at ages 10-12 years had a lower risk of breast cancer (odds ratio [OR] = 0.68; 95% confidence interval [CI] = 0.49-0.94). Women who had ever engaged in recreational physical activity had a reduced risk of breast cancer compared with inactive women (OR = 0.70; 95% CI = 0.56-0.88). Neither very early recreational activity (before age 20 years) nor recent activity (last 5 years) was associated with a greater reduction in risk than recreational activity in the intermediate period. Furthermore, women who started recreational activities after age 20 years and women who started earlier and continued their activities throughout adult life experienced a similar reduction in risk. Lean women, i.e., women with a body mass index (weight in kg/[height in m](2)) less than 21. 8 kg/m(2), appeared to have a lower risk associated with recreational physical activity than women with a body mass index greater than 24.5 kg/m(2) (OR = 0.57 [95% CI = 0.40-0.82] and OR = 0. 92 [95% CI = 0.65-1.29], respectively). CONCLUSIONS: Our findings support the hypothesis that recreational physical activity is associated with a decreased risk of breast cancer. Physical activity in early or recent life does not appear to be associated with additional beneficial effects.     

Does adequate physical activity attenuate the associations of alcohol and alcohol-related cancer mortality? A pooled study of 54 686 British adults

The potential of physical activity (PA) to attenuate the effects of alcohol consumption on the risks of alcohol-related cancer mortality is unknown. We used data from participants aged 30 years and over in 10 British population-based surveys (Health Surveys for England 1994, 1997, 1998, 1999, 2003, 2004, 2006 and 2008 and the Scottish Health Surveys 1998 and 2003). Alcohol-related cancer mortality included oral cavity, throat, larynx, oesophagus, liver, colorectal, stomach and female breast (conservative definition), and additionally pancreas and lung (broad definition). Alcohol consumption was categorised into six groups based on the UK units/week: (a) never-drinkers, (b) ex-drinkers, (c) occasional drinkers, (d) within guidelines (<14 UK units/week [women]; <21 UK units/week [men]), (e) hazardous (14-35 [women]; 21-49 [men]) and (f) harmful (>35 [women]; >49 [men]). PA was categorised using two dichotomous classifications based on the lower (7.5 Metabolic Equivalent Task [MET]-hours/week) and upper (15 MET-hours/week) recommended limits. Using Cox proportional hazard models, we found a strong direct association between alcohol consumption and mortality risk of alcohol-related cancers, with a significantly higher risk among ex-drinkers (Hazard ratio [HR] = 1.46, 95% confidence interval [CI] = [1.09, 1.94]), drinkers who consumed hazardous (HR = 1.39, 95% CI = [1.06, 1.83]) and harmful amounts of alcohol (HR = 1.62, 95% CI = [1.13, 2.30]) compared to never-drinkers in the fully adjusted model. The increased mortality risks were substantially attenuated when participants in these drinking groups exercised >7.5 MET-hours/week. PA could be promoted as an adjunct risk minimisation measure for alcohol-related cancer prevention.     

Physical activity and risk of endometrial cancer: a report from the Shanghai endometrial cancer study.

We evaluated the type and amount of physical activity associated with risk of endometrial cancer. In this population-based case-control study, in-person interviews were completed among 832 incident endometrial cancer cases and 846 age-matched controls. Physical activity from exercise, household activities, and transportation was assessed in adolescence and adulthood, as was lifetime occupational activity. Logistic regression was used to estimate adjusted odds ratios (OR) and 95% confidence limits (95% CL). Women reporting exercise participation in both adolescence and adulthood were at nearly a 40% reduced risk (OR, 0.63; 95% CL, 0.42-0.95), compared with women reporting no exercise in either life period. Postmenopausal women who initiated exercise in adulthood were also at reduced risk (OR, 0.76; 95% CL, 0.56-1.02). Reductions in risk were also observed for common lifestyle activities, including household activity (both life periods) and walking for transportation (adulthood). Examination of the independent and combined effect of exercise and lifestyle activities revealed that women with less active lifestyles but who reported exercise were at 35% reduced risk (OR, 0.65; 95% CL, 0.41-1.02), whereas nonexercisers with more active lifestyles were at 40% to 45% reduced risk. These findings suggest that both lifestyle activities of lower intensity (e.g., walking and doing household chores) and intentional exercise can reduce endometrial cancer risk.     

Relationships between polymorphisms in NOS3 and MPO genes, cigarette smoking and risk of post-menopausal breast cancer

NOS3 and MPO genes encode endothelial nitric oxide synthase and myeloperoxidase (MPO), respectively, which generate nitric oxide and reactive oxygen species. Because cigarette smoking generates reactive species, we hypothesized that NOS3 and MPO polymorphisms could influence susceptibility to breast cancer, particularly among smokers. We examined the associations between NOS3 Glu298Asp and MPO G-463A polymorphisms and breast cancer risk by cigarette smoking among post-menopausal women in the American Cancer Society's Cancer Prevention Study II Nutrition Cohort. Included in this analysis were 502 women who provided blood samples and were diagnosed with breast cancer between 1992 and 2001 and 505 cancer-free controls who were matched to the cases by age, race/ethnicity and date of blood donation. Genotyping for NOS3 and MPO was performed using TaqMan, and unconditional logistic regression was used to compute odds ratios (ORs) and 95% confidence intervals (CIs). No statistically significant relationships were found between NOS3 and MPO genotypes and breast cancer risk. When considering smoking, variant NOS3 genotypes (GT and TT) were significantly associated with reduced breast cancer risk among never smokers (OR = 0.67, 95% CI = 0.45-0.99), but were associated with higher risk among ever smokers (OR = 1.59, 95% CI = 1.05-2.41) and 2-fold increase in risk for those who smoked >10 cigarettes per day (OR = 2.19, 95% CI = 1.21-3.97). NOS3 genotypes appeared to be associated with risk of post-menopausal breast cancer among smokers, supporting the hypothesis that subgroups of women based upon genetic profiles may be at higher risk of breast cancer when exposed to tobacco smoke.     

Meeting the physical activity guidelines and survival after breast cancer: findings from the after breast cancer pooling project

The 2008 Physical Activity (PA) Guidelines recommend engaging in at least 2.5 h (10 MET-hours/week) of moderate intensity PA per week (defined as 4 METs) to reduce risk of morbidity and mortality. This analysis was conducted to investigate whether this recommendation can be extended to breast cancer survivors. Data from four studies of breast cancer survivors measuring recreational PA from semi-quantitative questionnaires a median of 23 months post-diagnosis (interquartile range 18-32 months) were pooled in the After Breast Cancer Pooling Project (n = 13,302). Delayed entry Cox proportional hazards models were applied in data analysis with adjustment for age, post-diagnosis body mass index, race/ethnicity, menopausal status, TNM stage, cancer treatment, and smoking history. Engaging in at least 10 MET-hours/week of PA was associated with a 27% reduction in all-cause mortality (n = 1,468 events, Hazard Ratio (HR) = 0.73, 95% CI, 0.66-0.82) and a 25% reduction in breast cancer mortality (n = 971 events, HR = 0.75, 95% CI 0.65-0.85) compared with women who did not meet the PA Guidelines (<10 MET-hours/week). Risk of breast cancer recurrence (n = 1,421 events) was not associated with meeting the PA Guidelines (HR = 0.96, 95% CI, 0.86-1.06). These data suggest that adhering to the PA guidelines may be an important intervention target for reducing mortality among breast cancer survivors.     

Case-control study of anthropometric measures and breast cancer risk

A population-based case-control study of 1,233 incident breast cancer cases and 1,241 controls was conducted in Alberta between 1995 and 1997 to examine the influence of anthropometric factors on the risk of breast cancer using several newly derived variables. Data on current height, weight and waist and hip circumference were collected by interviewers using standardized methods. Respondents recalled their body weight at each decade from age 20 to the referent year. Several variables were estimated, and unconditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (95% CIs). No statistically significant associations for any of the estimated variables with breast cancer risk for premenopausal women (462 cases, 475 controls) were found. The results for postmenopausal women (771 cases, 762 controls) in the highest vs. lowest quartiles were, for waist circumference, OR = 1.30 (95% CI 0.97-1.73); waist-hip ratio, OR = 1.43 (95% CI 1.07-1.93); weight gain since age 20, OR = 1.35 (05% CI 1.01-1.81); difference between maximum and minimum weights over adult lifetime, OR = 1.56 (95% CI 1.16-2.08); and the reference weight minus the minimum weight since age 20, OR = 1.47 (95% CI 1.10-1.97). Statistically significant trends in risk were observed for these variables. Effect modification with hormone replacement therapy use was found for most variables assessed for postmenopausal women, with much stronger associations found among never-users compared to ever-users. We found strong evidence that waist-hip ratio and weight gained over lifetime, as assessed by different variables, are postmenopausal breast cancer risk factors. These effects were independent of dietary intake and lifetime total physical activity.     

Recreational physical activity and risk of papillary thyroid cancer (United States)

Objective: Exercise has been hypothesized to influence cancer risk through a variety of mechanisms including hormonal, metabolic and immunologic effects, yet its relation with the risk of thyroid cancer has not been examined. We conducted a population-based case–control study in women aged 18–64 in three counties of western Washington State to assess the relation of recreational physical activity with risk of papillary thyroid cancer. Methods: Of 558 women with thyroid cancer of the follicular epithelium diagnosed during 1988–1994 who were identified as eligible, 468 (83.9%) were interviewed; this analysis was restricted to women with papillary histology (n = 410). Controls (n = 574) were identified by random digit dialing, with a response proportion of 73.6%. Logistic regression was used to calculate odds ratios (OR) and associated confidence intervals (CI) estimating the relative risk of papillary thyroid cancer associated with various aspects of recreational exercise. Results: Risk of thyroid cancer was reduced among women who reported that they engaged in regular recreational exercise during the 2 years before diagnosis relative to women who did not report exercise during that time period (OR = 0.76, 95% CI 0.59–0.98). A similar risk reduction was noted among women who reported having exercised regularly between ages 12 and 21 (OR = 0.83, 95% CI 0.64–1.1). However, no clear associations with aspects of recreational activity, including average hours exercised per week or weekly energy expenditure, were observed. Conclusions: These results provide some initial support for the hypothesis that physical activity may reduce risk of thyroid cancer.     

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.     

Moderate-to-vigorous intensity physical activity across the life course and risk of pre- and post-menopausal breast cancer

Moderate-to-vigorous intensity physical activity (MVPA) reduces breast cancer risk, although the effects of MVPA in different settings across the life course and how they may differ by menopausal status are unclear. This gap was addressed using data from a case–control study of 1,110 incident breast cancer cases and 1,172 cancer-free controls, frequency matched by age, from Vancouver and Kingston, Canada. In Vancouver, cases were recruited from the British Columbia Cancer Registry and controls from the Screening Mammography Program of British Columbia and in Kingston cases and controls were recruited from a breast assessment center. Lifetime leisure-time, household, and occupational MVPA energy expenditures were assessed in an open-ended questionnaire and mean weekly metabolic equivalent hours (MET-h/week) were calculated for the age periods 12–17, 18–34, 35–49, and ≥50 years and for the total lifetime. Odds ratios were estimated separately for pre- and for post-menopausal women using unconditional logistic regression. Among post-menopausal women, each of >22.9 MET-h/week of mean lifetime leisure-time MVPA (equivalent to running for 3 h) and >61.1 MET-h/week of mean lifetime household MVPA (equivalent to 24 h of moderate household work) reduced breast cancer risk by 40 %, compared to 0 MET-h/week of each. The respective ORs were 0.63 (95 % CI 0.42–0.94) and 0.58 (95 % CI 0.43–0.79). Among post-menopausal women, leisure-time MVPA after age 35 was more strongly associated with reduced breast cancer risk than MVPA in early life, while household MVPA was associated with reduced risk at all adulthood age periods. The weekly volume of leisure-time MVPA required to reduce post-menopausal breast cancer risk was consistent with amount recommended in the World Cancer Research Fund/American Institute for Cancer Research guidelines for cancer prevention.