An epidemiological case-control study of breast cancer and alcohol consumption

Community clinic-based lifestyle change for prevention of metabolic syndrome: Rationale, design and methods of the 'Vida Sana/healthy life' program

Purpose

and Objectives: The risk of diseases associated with Metabolic Syndrome (MetS) is higher for Hispanics living in the northeastern United States than for other racial and ethnic groups. Higher risk of diabetes, high blood lipids, obesity and limited access to continuity of care are all factors that also contribute to disproportionately poorer chronic disease outcomes for Hispanics.

Intervention approach

This article describes the planning and implementation of, and evaluation plans for the Vida Sana Program (VSP), a community-based group intervention created to address the identified MetS risks by encouraging healthier diet and physical activity behaviors among a low-income, largely Spanish speaking, and literacy limited uninsured population. Developed in response to recent calls for culturally-tailored interventions, VSP is conducted by trained bicultural/bilingual Navegantes, who deliver a culturally sensitive, fun and engaging eight-week, in-person educational series through group meetings. The intervention also includes a 40-page colorful, picture and graphic enhanced booklet to be used in the group setting and at home. The intervention focused on screening for MetS-associated disease risk factors, understanding chronic disease management, encouraging medication adherence, increasing physical activity, and healthful dietary changes such as limiting alcohol, sodium, unhealthy fats and excess carbohydrate intake, while emphasizing portion control, whole grains and healthy fats.

Conclusions

This creative, community-based approach fills an important gap in the community and in the public health literature, is well liked by health literacy limited patients, and will provide an important model of successfully engaging the Hispanic community on these important health issues.

Alcohol consumption and breast cancer risk among women in three sub-Saharan African countries

Background

Alcohol drinking is linked to the development of breast cancer. However, there is little knowledge about the impact of alcohol consumption on breast cancer risk among African women.

Methods

We conducted a case-control study among 2,138 women with invasive breast cancer and 2,589 controls in Nigeria, Cameroon, and Uganda from 1998 to 2013. A structured questionnaire was used to collect information on alcohol consumption, defined as consuming alcoholic beverages at least once a week for six months or more. Logistic regression was used to estimate adjusted odds ratio (aOR) and 95% confidence interval (CI).

Results

Among healthy controls, the overall alcohol consumption prevalence was 10.4%, and the prevalence in Nigeria, Cameroon, and Uganda were 5.0%, 34.6%, and 50.0%, respectively. Cases were more likely to have consumed alcohol (aOR = 1.62, 95% CI: 1.33–1.97). Both past (aOR = 1.54; 95% CI: 1.19–2.00) and current drinking (aOR = 1.71; 95% CI: 1.30–2.23) were associated with breast cancer risk. A dose-response relationship was observed for duration of alcohol drinking (P-trend <0.001), with 10-year increase of drinking associated with a 54% increased risk (95% CI: 1.29–1.84).

Conclusion

We found a positive relationship between alcohol consumption and breast cancer risk, suggesting that this modifiable risk factor should be addressed in breast cancer prevention programs in Africa.

Patterns of alcohol (especially wine) consumption and breast cancer risk: a case-control study among a population in Southern France

PURPOSE

The association between alcohol consumption and breast cancer has been largely investigated, but few studies have investigated the effects of average intake when the pattern of drinking is taken into account. We sought to examine the association between drinking pattern of alcoholic beverages, particularly wine, and breast cancer using different statistical approaches.

METHODS

Our study included 437 cases of breast cancer, newly diagnosed in the period 2002-2004, and 922 residence- and age-matched controls.

RESULTS

Women who had an average consumption of less than 1.5 drinks per day had a lower risk (odds ratio [OR] = 0.58, 95% confidence interval [CI] = 0.34-0.97) when compared with nondrinkers. This protective effect was due substantially to wine consumption since the proportion of regular wine drinkers is predominant in our study population. Furthermore, women who consumed between 10 and 12 g/d of wine had a lower risk (OR = 0.51; 95% CI = 0.30-0.91) when compared with non-wine drinkers. Above 12 g per day of wine consumption, the risk of breast cancer increased, but the association was nonsignificant.

CONCLUSIONS

Although no association between the pattern of total alcohol consumption and breast cancer was found, the type of alcoholic beverage seemed to play an important role in this association. Our results support the hypothesis that there is a threshold effect that risk decreased or was not modified for consumption under a certain threshold. Above that threshold, risk increased, however. The drinking pattern of each type of specific beverage, especially wine, seems important in terms of alcohol-breast cancer association. Low and regular wine consumption does not increase breast cancer risk.

Alcohol intake in adolescence and mammographic density

Adolescent exposures may be important in the development of breast cancer later in life. We examined the association of adolescent alcohol consumption and adult mammographic density, a strong risk factor for breast cancer. Women within the Minnesota Breast Cancer Family Cohort with detailed mammogram and risk factor information (n = 1,893) formed our sample. Breast cancer cases were excluded. Adolescent alcohol consumption (before age 18) was solicited through a mailed questionnaire. Percent density (PD) was estimated using the computer-assisted thresholding program, Cumulus. Statistical analyses were performed using linear mixed effect models. Women who reported ever drinking alcohol before age 18 (n = 390; 21%) had a higher unadjusted PD than women who never drank during adolescence (mu(unadj) = 26.5% vs. 22.2%), but this difference disappeared with adjustment for risk factors for mammographic density (mu(adj) = 21.0% vs. 21.2%, p = 0.94). Adult PD was not associated with age at initiation, amount of alcohol consumed at one sitting or frequency of alcohol use before age 18. The lack of differences was seen across strata of menopausal status. There was suggestion of higher PD among heavy and more frequent drinkers (24.0%, 95% CI 21.1-26.8%) compared to lighter (21.3%, 95% CI 20.3-22.3%) and never drinkers (21.4%, 95% CI 20.9-21.9%) and also among regular adolescent drinkers who were daily or weekly adult drinkers (25.0%, 95% CI 23.0-27.0%) compared to less regular drinkers in these 2 time periods (23.0-23.4%). However, these associations were not statistically significant (p = 0.27 and p = 0.22, respectively). In summary, there was no evidence that adolescent alcohol use was associated with large and persistent effects on adult PD.

Investigation of systemic folate status, impact of alcohol intake and levels of DNA damage in mononuclear cells of breast cancer patients

Folate is required for DNA synthesis, repair and methylation. Low folate status has been implicated in carcinogenesis, possibly as a result of higher rate of genetic damage. The aim of this study is to compare folate status and levels of DNA damage between breast cancer and benign breast disease control patients. Fasting blood samples from 64 histologically confirmed untreated breast cancer patients (mean age 57 years) and 30 benign breast disease control patients (mean age 51 years) were obtained. Red cell folate (RCF) and plasma homocysteine were measured. Mononuclear cells (MNC) were isolated for genetic damage analysis using the basic alkaline comet assay. Results are expressed as tail moment. Data were log transformed as appropriate before analysis for normalisation purposes. The geometric mean (95% confidence interval) of RCF (ng ml⁻¹) in breast cancer patients was 339.07 (333.3–404.6) vs 379.5 (335.8–505.2) in control patients (P=0.24). Corresponding plasma homocysteine concentrations (μmol l⁻¹) were 11.9 (10.6–16.4) vs 10.1 (9.3–11.9) (P=0.073), respectively. The mean tail moment (s.d.) of DNA damage in MNC of breast cancer patients detected by the basic comet assay was 1.4 (0.66) vs –0.17 (0.79) in controls (P<0.0001, t-test), the modified comet assay ‘endonuclease III (Endo III)’ was 1.7 (0.70) vs 0.86 (0.81) (P<0.0001, t-test), and the modified comet assay ‘formamidopyrimidine glycosylase (FPG)’ was 1.6 (0.62) vs 0.99 (0.94) (P<0.0001, t-test). There was a significant negative correlation between RCF levels and DNA damage detected by modified comet assay ‘FPG’ (Pearson Correlation Coefficient r²=−0.26, P=0.02) and DNA damage was found to be significantly higher in MNC of breast cancer patients compared to benign breast disease control patients. Breast cancer patients tended to have lower RCF levels and higher levels of plasma homocysteine, but these differences were not significant. The study provides preliminary evidence that reduced folate status may be implicated in the aetiology of breast cancer perhaps by increasing the in vivo level of genetic instability.

Alcohol Exposure and Breast Cancer: Results of the Women's Contraceptive and Reproductive Experiences Study

Objectives: To explore associated biological outcomes and clarify the role of timing of exposure in the alcohol-breast cancer relationship.

Methods: In a population-based study of 4,575 women ages 35 to 64 years diagnosed with invasive breast cancer between 1994 and 1998 and 4,682 controls, we collected details of lifetime alcohol use and factors that could confound or modify the alcohol-breast cancer relationship. We used conditional logistic regression to compute the odds of breast cancer among drinkers relative to nondrinkers at all ages and at ages 35 to 49 and 50 to 64 years separately.

Results: Recent consumption (at reference age minus two) of ≥7 drinks per week was associated with increased risk [odds ratio (OR), 1.2; 95% CI, 1.01-1.3] and evidence of dose response was observed. Most of the excess was observed among women ages 50-64 years (OR 1.3; 95% CI, 1.1-1.6), although the test for age interaction was not statistically significant. Exposure later in life seemed more important than early exposure. Excess breast cancer associated with recent consumption was restricted to localized disease. When outcome was examined according to tumor hormone receptor status, highest risks were observed for estrogen receptor–positive/progesterone receptor–negative tumors (OR 1.6; 95% CI, 1.2-2.3).

Conclusions: The effect of timing of alcohol exposure on breast cancer risk is complicated and will require additional study focused on this one issue. Further work is needed to explain how alcohol exposure, sex hormones, and tumor receptor status interact.

Derivation of tolerable upper alcohol intake levels in Germany: a systematic review of risks and benefits of moderate alcohol consumption

BACKGROUND

The objective of this study is to weigh the risks of moderate alcohol consumption against its benefits and, as a result, to derive tolerable upper alcohol intake levels (TUALs) for the German adult population.

METHODS

Human studies assessing the effects of moderate alcohol consumption (< or = 40 g/day) on coronary heart disease, stroke, blood pressure, diseases of the liver, gallbladder, bile duct, and pancreas, cancer of the mouth/pharynx/larynx/oesophagus, stomach, colon/rectum, and breast, foetal alcohol syndrome/foetal alcohol effects, as well as all-cause mortality, published in the 10-15 years before 1999, have been systematically reviewed. The quality of studies has been evaluated using a self-constructed evaluation scheme. As a result of comparing the critical endpoints of alcohol intake related to morbidity and mortality, the TUALs have been derived.

RESULTS

The TUALs have been set at 10-12 g/day for healthy women and 20-24 g/day for healthy men of the adult population (18 years and older). Additional guidelines on alcohol use have been defined, taking into account further important aspects like alcohol consumption patterns and high-risk groups.

CONCLUSIONS

The TUALs are not intended to be recommended intake levels. However, if the TUALs and the additional guidelines are followed, a relation of alcohol consumption to an increased risk of alcohol-associated diseases is unlikely for the majority of the population.

Lifetime alcohol consumption and postmenopausal breast cancer rate in Denmark: a prospective cohort study

Alcohol intake may be one of the few modifiable risk factors for breast cancer. In a prospective cohort of 29,875 women with 423 cases of breast cancer during 1993-2000, we examined the relationship between postmenopausal breast cancer incidence rate and alcohol consumption in different life periods. When alcohol intake during four age ranges, twenties, thirties, forties and fifties was evaluated, only the intake in the fifties increased the risk of breast cancer [rate ratio (RR)=1.12 (95% CI: 1.05-1.19)] per 10 g/d increase in alcohol intake. After adjustment for intake at study entry, this association was no longer present [RR=1.01 (95% CI: 0.91-1.13)]. The cumulative lifetime alcohol intake, adjusted for recent intake, showed no association with postmenopausal breast cancer risk. Recent alcohol intake, adjusted for the alcohol intake in the other life time periods, showed a significant association of RR=1.09 (95% CI: 1.00-1.18) per 10 g/d. There was no indication of a higher risk among women with early drinking start, nor did women who started to drink before their first birth have a higher risk than women who started to drink later in life. Our results suggest that baseline intake of alcohol is a more important determinant of postmenopausal breast cancer risk than earlier lifetime exposure.

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.

Lifetime alcohol consumption and breast cancer: a case-control study in Finland

OBJECTIVE

To study the association between lifetime alcohol consumption and the risk of breast cancer.

DESIGN AND SETTING

A case-control study carried out in eastern Finland. Information about alcohol consumption was obtained by two methods: a self-administered food frequency questionnaire (FFQ) including alcohol consumption during the previous 12 months, and a lifetime alcohol consumption questionnaire (AQ) which was administered by the study nurse.

SUBJECTS

The study consisted of 301 breast cancer cases (25-75 years old) and 443 population controls.

RESULTS

The subjects reported higher current alcohol consumption in the AQ compared to the FFQ. According to the AQ, premenopausal cases consumed on average 28 g and controls 24 g alcohol week(-1); in postmenopausal women the values were 15 and 14 g, respectively. About 30% of premenopausal and 60% of postmenopausal women were classified as non-drinkers. The correlation for current alcohol consumption between the FFQ and the AQ was 0.80 in premenopausal women but only 0.40 in postmenopausal women. Current alcohol consumption seemed to influence the reporting of total lifetime alcohol consumption. Current alcohol consumption was not associated with the risk of breast cancer either in premenopausal or postmenopausal women; neither were associations found between alcohol consumption at age of first use, use before the age of 30, or total lifetime alcohol consumption and the risk of breast cancer.

CONCLUSIONS

On average, one to three drinks per week did not increase the risk of breast cancer in this study. Consumption levels were, however, too low to exclude increased risk with high regular consumption. Further research is necessary on lifetime alcohol consumption.

Alternative strategies for selecting population controls: comparison of random digit dialing and targeted telephone calls

PURPOSE

This project was carried out to identify a valid framework for selecting controls to be used in a population-based case-control study of breast cancer, and to compare participation rates and characteristics between women contacted using a standard random digit dialing (RDD) strategy and those who were sent a letter of presentation prior to telephone contact (targeted telephone calls, TTC).

METHODS

Twelve hundred women, ages 20-74, were sampled from the Department of Motor Vehicles (DMV) and Health Care Financing Administration (HCFA) records. Women for whom telephone numbers were obtained (N = 771) were randomly assigned to RDD or TTC. The respondents participated in a brief telephone interview. Odd ratios (OR) and their 95% confidence intervals (CI) were used to estimate differences in characteristics of the respondents between the two contact strategies.

RESULTS

Telephone numbers were obtained for 79% of women aged > or = 55 years and for only 38% of women aged < 55 years. Interviews were obtained for 48% of women for whom we obtained telephone numbers, and for 77% of women for whom eligibility was confirmed via telephone contact. Participation of target women appeared to be higher for the TTC than the RDD group (42% vs. 35%, p = 0.054). Among respondents who were > or = 55 years old, those in the TTC group were 80% more likely (OR = 1.8, 95% CI: 0.9-3.4) to report a serious medical condition than women in the RDD group, 60% less likely (OR = 0.4, 95% CI: 0.2-1.0) to report having used oral contraceptives, and 80% less likely (OR = 0.2, 95% CI: 0.1-0.5) to report having had breast surgery.

CONCLUSIONS

Characteristics of respondents differed according to method of contact. These differences, along with the sampling frame used, should be considered when interpreting findings of case-control studies.

Estrogen, alcohol and breast cancer risk

Estrogen replacement has been used for many years to reverse the hypoestrogenic symptoms of menopause and prevent osteoporosis. Studies have found that estrogen replacement also decreases cardiovascular risk. In addition, social use of alcohol has been found to decrease cardiovascular risk. Therefore, both estrogen replacement therapy and alcohol use have been proposed to have cardiovascular benefits, and are often used in combination. Epidemiologic evidence indicates that estrogen replacement therapy after menopause increases breast cancer risk. Regular alcohol consumption is also associated with increase in risk. However, interactions between the two are poorly understood. In addition, if alcohol alters circulating estrogen levels in estrogen users, this may have implications in terms of altering the risks:benefit ratio of estrogen replacement in an undesirable direction. For example, there are data suggesting that the use of both alcohol and estrogen may increase breast cancer risk more than the use of either one alone. Data support both acute and chronic effects of alcohol in raising circulating estrogen levels in premenopausal women on no hormonal medications. In postmenopausal women studies focusing on acute effects of alcohol on estrogen metabolism indicate that alcohol has a much more pronounced effect in women using estrogen replacement than in those who do not. Studies evaluating chronic effects of alcohol ingestion on circulating estrogens in postmenopausal women are needed.

Alcohol consumption and risk of breast cancer: a multicentre Italian case-control study

The relationship between alcohol consumption and breast cancer risk was investigated using data from a co-operative case-control study conducted in Italy between 1991 and 1994 on 2569 incident, histologically confirmed breast cancer cases and 2588 controls in hospital for acute, non-neoplastic, non-hormone related conditions. Overall, 915 (38%) cases and 1048 (43%) controls were abstainers. Compared with them, the odds ratio (OR), adjusted only for age, was 1.31 (95% confidence interval (CI) 1.13-1.53) for drinkers and became 1.39 (95% CI 1.(1)21-1.60) after correction for measurement error. The multivariate OR was 1.21 for drinkers of < or = 5.87 g/day and 1.23, 1.19, 1.21, 1.41 for drinkers of 5.88-13.40, 13.41-24.55, 24.56-27.60, > 27.60 g/day, respectively. The trend in risk was significant (chi 2 = 12.28, P < 0.0005). The association was apparently stronger in premenopausal women (OR = 1.80 for > 27.60 g/day). Considering the different types of alcoholic beverages (wine, beer, digestives, grappa and other spirits), a significant direct trend in breast cancer risk was seen for wine with an OR of 1.27 (95% CI 1.06-1.53) for the category > 26.34 g/day. The ORs were also above unity for beer, grappa, digestives and spirits drinkers. No appreciable interaction was observed between alcohol drinking and body mass index, smoking, or any other covariate considered. Thus, the present data, based on a validated alcohol consumption questionnaire and on a population characterised by a relatively high alcohol consumption in women, confirmed that alcohol drinking is moderately related to breast cancer risk. If causal, this association could explain 12% (95% CI, 5-19%) of breast cancers in Italy, thus representing one of the major avoidable risk factor for breast cancer.

Lifetime alcohol consumption and risk of breast cancer

The relation of lifetime alcohol intake to risk of breast cancer in pre- and postmenopausal women was examined in a case-control study in western New York. Cases with incident primary histologically confirmed breast cancer diagnosed during the period 1986-1991 (n = 740) and controls, frequency age-matched women drawn from New York state driver's license records (age < 65 yrs) and from records of the Health Care Finance Administration (age > or = 65 yrs, n = 810), were interviewed regarding intake of wine, beer, and hard liquor 2, 10, and 20 years ago and at 16 years of age. Although women in this study had generally low intakes of alcohol, there was little evidence of increased risk of breast cancer with intake of alcohol at any of the time periods or with an index of total lifetime intake. There was a weak indication of an increase in risk with beer for intakes of at least one drink per day. This risk was evident for 2, 10, and 20 years ago but not at 16 years of age. In this group with relatively low intakes of alcohol, evidence was weak for an association of increased risk of breast cancer with intake of alcohol, with the possible exception of a weak association with beer intake.

Alcohol and breast cancer. Where are we now and where do we go from here?

The alcohol-breast cancer hypothesis is important because (1) breast cancer is a major source of morbidity and mortality, (2) alcohol consumption is common, and (3) drinking is modifiable. Reports from more than 50 epidemiologic investigations of this hypothesis have now appeared. A recent metaanalysis of these studies indicates both a modest positive association between alcohol and breast cancer (an approximately 25% increase in risk with daily intake of the equivalent of two drinks) and a dose-response relation. Data suggest that risk increases with consumption of alcohol in general, regardless of beverage type. Several factors, including age, weight, and estrogen usage, have been shown to modify this relation in some studies. The authors discuss a series of methodologic issues in the study of alcohol and breast cancer. These include error in alcohol assessment, difficulties in evaluating small relative risks, and the potential for confounding. Several biologic mechanisms could account for an alcohol-breast cancer relation, with increasing attention being paid to a possible mediating effect of reproductive steroid hormones. Animal studies are a relatively recent development in this area; results have been mixed. Incorporation of more refined temporal, quantitative, and qualitative indicators of alcohol exposure in future epidemiologic studies would be valuable, as would further exploration of the endocrine and other metabolic effects of moderate alcohol consumption. The alcohol-breast cancer hypothesis remains intriguing, but causality has not been established.

Nutritional risk factors for breast cancer

The observation of large differences in breast cancer rates between countries has led to the hypothesis that excessive intake of dietary fat is an important risk factor for breast cancer in women. Case-control and prospective studies, however, generally have failed to show associations between dietary fat and breast cancer risk. There therefore is only weak evidence that modest reductions in fat intake (for instance to levels of 30% of caloric intake from fat) will reduce breast cancer risk. The possible benefits of lowering fat intake to levels substantially below 30% of calories will need to be tested in a randomized trial. In the meantime, the possible roles of micronutrient imbalances and childhood nutritional factors need to be studied better. Obesity is related to breast cancer in a complex way that suggests that a hormonal correlate of excessive body weight might affect breast cancer growth and metastasis. The potential benefit of intentional weight loss as an adjunct breast cancer treatment deserves further study. Many studies have suggested that drinking alcohol, even at modest levels, might increase breast cancer risk. Because the potential benefits of modest levels of alcohol for cardiovascular disease may outweigh the risk for breast cancer, recommendations for total alcohol abstinence may be premature for women with an average breast cancer risk. Women at unusually high risk for breast cancer who have a lower-than-average risk for cardiovascular disease, however, might make an informed decision to abstain from alcohol intake. Following current dietary advice to increase the amount of fruits, vegetables, and whole grains in the diet while reducing fats is certainly prudent for women to reduce their risk of several chronic disease, but current data points to the somber conclusion that such changes probably will have little effect on breast cancer risk.

Diet and health: what should we eat?

Many recent studies have implicated dietary factors in the cause and prevention of important diseases, including cancer, coronary heart disease, birth defects, and cataracts. There is strong evidence that vegetables and fruits protect against these diseases; however, the active constituents are incompletely identified. Whether fat per se is a major cause of disease is a question still under debate, although saturated and partially hydrogenated fats probably increase the risk of coronary heart disease. One clear conclusion from existing epidemiologic evidence is that many individuals in the United States have suboptimal diets and that the potential for disease prevention by improved nutrition is substantial.

Alcoholic beverages and breast cancer: some observations on published case-control studies

We identified 38 case-control studies investigating possible associations between alcoholic beverage consumption and cancer of the female breast. Each study was characterized according to design features such as: control type (hospital or community based), risk factors controlled for, matching strategy, and statistical power. We examined the effect of these design variables on several outcome variables including identification of any significant elevation in odds ratio and characterization of any dose-response effect. The major finding of this study is that of a striking difference between hospital and community based controlled studies with respect to (1) the level of any estimated dose-response effect, and (2) the finding of statistically significant elevations in odds ratios at levels of consumption below 4 drinks per week. In summary, the generally weak associations reported in these case-control studies along with the measurement and/or selection biases implied by our findings would lead one to the conclusion that present evidence does not support a causal association. This conclusion seems to be in accord with results from cohort studies and with similar conclusions from several other reviews.

Alcoholic beverage consumption in relation to risk of breast cancer: meta-analysis and review

The objective was to evaluate the association between alcohol consumption and risk of breast cancer. Data from 38 epidemiologic studies on alcohol consumption in relation to risk of breast cancer in women were included in a meta-analysis. A qualitative literature review also was conducted. The results showed strong evidence of a dose-response relation; however, the slope of the dose-response curve was quite modest. For example, daily consumption of one alcoholic drink was associated with an 11 percent increase (95 percent confidence interval, seven to 16 percent) in the risk of breast cancer compared with nondrinkers. An explanation for the marked variation in results across studies was not found. The modest size of the association and variation in results across studies leave the causal role of alcohol in question. The evidence that alcohol consumption affects the risk of breast cancer, however, appears to be growing stronger.

Recall and selection bias in reporting past alcohol consumption among breast cancer cases

Recall and selection bias are well-recognized potential problems in case-control studies of alcohol and cancer, but few analyses have attempted to assess the direction and the magnitude of these potential biases. We thus examined alcohol consumption in relation to risk of breast cancer using dietary questionnaires administered both before and after the diagnosis of breast cancer in the Nurses' Health Study (United States). Among cohort members who completed a dietary questionnaire in 1986 and who were free of cancer, 616 were diagnosed with breast cancer during follow-up to December 1989. These cases and 1,277 controls (a random sample of cohort members who did not develop cancer up to 1990) then were sent another questionnaire inquiring about their diet in 1985. Four hundred and ninety-four cases (80.2 percent) and 999 controls (78.2 percent) responded to the second questionnaire. The analysis based on the prospective (1986) questionnaire demonstrated an elevated risk of breast cancer among women who drank 30 or more g of alcohol daily (about two drinks) relative to nondrinkers (odds ratio [OR] = 1.55, 95 percent confidence interval [CI] = 1.01-2.39). The analysis based on the retrospective questionnaire also indicated a similar but slightly attenuated elevation of risk of breast cancer among women who drank at least 30 g daily (OR = 1.42, CI = 0.85-2.40). In these data, bias due to selection and recall had only minor effects on reported intake of alcohol consumption.

Breast cancer in Denmark. Incidence, risk factors, and characteristics of survival

In Denmark, incidence of female breast cancer remained constant from 1943 to around 1960, whereafter a steady increase has occurred, the level today being about 50% higher than in 1960. No equivalent rise has been observed for breast cancer mortality. Influence of hormonal and dietary factors on breast cancer risk and survival was evaluated in a combined population-based case-control and follow-up study, including 2,445 women, aged less than 70 years, diagnosed with breast cancer in Denmark between 1 March 1983 and 31 August 1984, identified from the files of the nation-wide clinical trial of the Danish Breast Cancer Co-operative Group (DBCG) and the Danish Cancer Registry. The control group was an age-stratified random sample of the general female population, selected from the Central Population Register. Data on risk factors were collected by self-administered questionnaires. Clinical and pathological tumour characteristics derived from DBCG. The case-control analysis confirmed an overall increased risk of breast cancer associated with urban residence, high social status, nulliparity, early age at menarche, late age at natural menopause, hormonal replacement therapy, high dietary fat intake, and high alcohol consumption in a subgroup. It failed to detect an association with age at first childbirth, oral contraceptives, smoking, intake of vegetables, tea, coffee, and sweeteners. Survival was determined by tumour size, skin invasion, number of positive lymph nodes, and grade. There was no relation between survival and reproductive or hormonal factors, dietary variables, alcohol consumption, or smoking. However, a complex relationship may exist between survival and body mass index.

Alcohol consumption and breast cancer risk in Denmark

The influence of alcohol consumption on breast cancer risk was evaluated in a population-based case-control study, including 1,486 cases diagnosed over a one-year (1983-84) period in Denmark. Cases were identified from the files of the nationwide 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 questionnaires. The association of alcohol consumption with breast cancer risk varied with age and dietary fat intake. Among women aged 50-59 years, with a fat intake in the lowest quartile, the risk of breast cancer increased with increasing consumption of alcohol. A consumption of 24 g or more per day was associated with an 18-fold increased risk compared with abstainers. For women in other age groups, alcohol consumption had no significant association with breast cancer risk.