Active smoking increases breast cancer risk-Active smoking and risk of breast cancer in a Danish nurse cohort study

No scientific consensus has been reached on whether active tobacco smoking causes breast cancer. We examine the association between active smoking and breast cancer risk in Denmark, which has some of the highest smoking and breast cancer rates in women worldwide. We obtained data on incidence of breast cancer from Danish Cancer Registry until , and used Cox regression models to analyze the association between smoking and breast cancer. Of 21, women mean age Association between smoking and breast cancer was not modified by menopausal status, obesity, alcohol or hormone therapy use, and seemed to be limited to the estrogen receptor positive breast cancer subtype.

Active smoking increases breast cancer risk

Active smoking increases breast cancer risk

Active smoking increases breast cancer risk

Eur J Surg Swinging watertown. Cancer Treat Rev. Danish nurses have been found to live a generally healthier lifestyle than a representative sample of Danish women, as they smoked less and had higher physical activity levels, although they consumed more alcohol. Breast cancer risk following Hodgkin lymphoma radiotherapy in relation to menstrual and reproductive factors. Volume E. Hines, Anna R. This referral method continued with subsequent recruits [ 21 ]. Objectives: To examine the association between time of smoking initiation and both the independent and joint effects of active and passive tobacco smoke exposure and the risk of breast cancer in a sample of Ontario women. Cigarette smoking breqst risk of fatal breast cancer.

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Tobacco smoke contains at least 20 chemical compounds that induce mammary cancers in rodents 34 International Agency for Research on Cancer. Therefore, some information may be out of date at this time. Find information on secondhand smoke exposure also called passive smoking and the risk of breast cancer. Associations for former smoking were weaker but still positive in 13 of 15 studies 9—1744—48excluding only the Canadian National Breast Screening Study 10 and the Members Active smoking increases breast cancer risk a Large Prepaid Health Plan in Northern California Kaiser2 44 cohorts, which found no association and an inverse association, respectively, with former smoking Women in this analysis were drawn from the bresst female participants in the CPS-II Nutrition Cohort, a prospective study of cancer incidence and mortality established in as a subgroup of a larger mortality study initiated in In addition to benefiting your breast health, stopping smoking will help protect you from a number of other cancers and also protect your heart. Having a risk factor does not mean you will get the disease, and not all risk factors have the same effect. Three reviews of secondhand smoke SHS increses breast cancer each came to different conclusions. Advanced Search.

Plausible biological reasons exist regarding why smoking could affect breast cancer risk, but epidemiological evidence is inconsistent.

  • Four authoritative reviews of active smoking and breast cancer have been published since , but only one considered data after and conclusions varied.
  • Mia M.
  • Studies have shown that your risk for breast cancer is due to a combination of factors.
  • This summary table contains detailed information about research studies.
  • The precise connection between smoking and breast cancer is still unclear, but there does appear to be some sort of link.
  • .

No scientific consensus has been reached on whether active tobacco smoking causes breast cancer. We examine the association between active smoking and breast cancer risk in Denmark, which has some of the highest smoking and breast cancer rates in women worldwide. We obtained data on incidence of breast cancer from Danish Cancer Registry until , and used Cox regression models to analyze the association between smoking and breast cancer.

Of 21, women mean age Association between smoking and breast cancer was not modified by menopausal status, obesity, alcohol or hormone therapy use, and seemed to be limited to the estrogen receptor positive breast cancer subtype.

Active smoking increases risk of breast cancer, with smoking before first birth being the most relevant exposure window. Tobacco smoke is the leading cause of cancer worldwide and contains over known carcinogenic substances.

However, a meta-analysis of 53 epidemiological studies found no impact of smoking on the risk of breast cancer. Recent large prospective cohort studies [ 6 — 13 ] with detailed data on active smoking consistently report an increased breast cancer risk associated with longer duration and higher intensity of smoking, and indicating that smoking early in life, before first childbirth, is the most relevant exposure window.

In Denmark, with some of the highest smoking prevalence and breast cancer incidence in the world, the impact of smoking on breast cancer has been debated due to conflicting results from the early Danish studies. Nurses filled out the questionnaire at recruitment on working conditions, weight and height, lifestyle diet, active smoking, alcohol consumption, and leisure time physical activity , parity, age at first birth, age of menarche and menopause, and use of oral contraceptives OC and HT.

We utilized baseline information from 19, or for 28, female nurses. Using a unique identification number we linked the cohort participants to Civil Registration System [ 19 ] to obtain vital status information at 31st December active, date of death or emigration. Pack-years of smoking before 1st childbirth, between 1st childbirth and menopause, and after menopause was calculated from information on age of smoking onset, age at 1st birth, and age at menopause in parous postmenopausal women.

No information was collected on passive smoking in the Danish Nurse Cohort. We linked the records of 28, nurses using unique identification number to the Danish Cancer Register [ 20 ] to extract all cancer diagnoses until First, we extracted data for nurses with diagnoses for any other than non-melanoma skin cancer cancer before baseline 1st April or 1st April , these nurses were excluded from the analyses.

Secondly, among nurses without prior cancer, we extracted primary invasive breast cancer diagnoses ICD codes C50 , as the main outcome, and any other cancer other than non-melanoma skin cancer between cohort baseline 1st April or 1st April and 31st December Furthermore, we extracted data on breast cancer subtype by estrogen receptor ER and progesterone receptor PR status from the clinical database of the Danish Breast Cancer Cooperative Group.

The follow-up started on the cohort baseline date 1st April or 1st April and ended at the date of breast cancer event or other cancer diagnoses except non-melanoma skin cancer , death, emigration, or December 31, censoring , whichever came first. We evaluated the effect of active smoking status, duration, intensity, and onset in separate models. We performed tests for trend by using the ordered category, including the reference as a continuous variable in the Cox model. We checked for the proportional hazards assumption for all smoking variables and confounders based on scaled Schoenfeld residuals.

Analyses were performed in Stata The study was entirely based on a data from registers and approved by the Danish Data Inspection Agency, which by Danish law serving as ethical approval of register-based research. Thus, no contact has been taken with participating women, relatives or their practicing doctors, and no consent was needed. Of the total 28, nurses in the Danish Nurse Cohort, we excluded 4 due to inactive emigrated vital status and with cancer diagnosis before cohort baseline, and with missing information on one or more covariates.

Of the 21, nurses in the main analyses developed breast cancer during the mean follow-up of The mean age at baseline was Compared with women who remained free of breast cancer, those who developed the cancer were more likely to be nulliparious, postmenopausal, obese, heavy alcohol drinkers, slightly physically active and HT users, but less likely to work night shifts, and use OC.

SD standard deviation; a in ever smokers. The majority of nurses Mean duration of smoking in ever smokers was Smoking duration and intensity were higher in nurses who developed breast cancer than in those who were free of breast cancer. The majority of women started smoking early, before 1st childbirth or before age 21 nulliparous women. Whilst smoking rates and smoking intensity were lower in younger, as compared to older birth cohorts, the age at smoking initiation decreased, from Accordingly, number of women smoking before 1st childbirth increased.

Notably, also the use of HT and alcohol was higher in younger than in older birth cohorts. Compared to never smokers, we found an increased risk of breast cancer in ever HR: 1. Compared to parous never smokers, the risk of breast cancer seemed weaker in parous ever smokers who started smoking before 1. Nulliparous ever smokers had also increased risk of breast cancer, similar to that observed in parous women 1. When limiting analyses to the 12, women who were postmenopausal at the time of recruitment, we found that both women who started smoking before 1.

Finally, when considering smoking intensity in different periods of life related to 1st childbirth and menopause among parous postmenopausal women, the strongest effect of smoking on breast cancer was observed with smoking before 1st childbirth 11—20 pack-years: 2.

Association between active smoking and breast cancer in 21, women in the Danish Nurse Cohort. HR hazard ratio, CI confidence interval a Adjusted for age, no of births, Body Mass Index, physical activity, alcohol use, oral contraceptive use, age at menarche, menopause, age at 1st birth, parity, number of birth, hormone therapy use, and night shift work.

Effect modification of association between active smoking and breast cancer in 21, women in the Danish Nurse Cohort by menopausal status, obesity, alcohol consumption and hormone therapy use. Association between ever vs. The strongest risk was detected in parous women who smoked heavily before 1st childbirth.

Our results confirmed the association between active smoking and breast cancer incidence reported in almost all recent prospective cohort studies. The strong effects of smoking observed in both, our and in the Norwegian cohorts both that part of EPIC study [ 11 ]. Notably, no association between smoking and breast cancer was found current vs. These younger birth cohorts started smoking earlier and were able to accumulate more years of smoking before the 1st childbirth than the older birth cohorts: on average 7.

We found the highest risk of breast cancer related to smoking heavily before the 1st childbirth, in agreement with existing evidence. In contrast to the EPIC study, [ 11 ] no protective effect of smoking in postmenopausal age was found in either American [ 6 ] or Danish nurses.

As alcohol is an established risk factor for breast cancer, and as alcohol and smoking often come together, the possible confounding by alcohol of the effect of smoking on the risk of breast cancer has been debated in literature.

Alcohol has also been previously shown to be an independent risk factor for breast cancer in the Danish Nurse Cohort. Our risk estimates were adjusted for intensity of alcohol consumption. The available data thus indicate that the effect of smoking on breast cancer risk is independent of the effect of alcohol. We contribute with novel data on smoking and subtypes of breast cancer, as only a few studies have previously included this information.

Strengths of this study include data from a large prospective nationwide cohort with comprehensive follow-up of both vital status and incident breast cancer cases from linkage with nationwide registers.

Exposure information from the cohort was expected to be valid as already known associations between breast cancer and, for instance, alcohol use [ 26 ] and HT [ 26 — 28 ] have already been documented in this cohort.

This means that potential confounding not controlled for will affect our results less than is the case in the studies where smokers constitute a smaller, and thus a more marginalized group of women.

The main limitation was the exposure misclassification as the smoking exposure was based on questionnaires at the time of recruitment, without follow-up, and the lack of information on passive tobacco smoke. Danish nurses have been found to live a generally healthier lifestyle than a representative sample of Danish women, as they smoked less and had higher physical activity levels, although they consumed more alcohol.

The risk increases both with smoking duration and smoking intensity. The highest risk was seen in women with more than 10 pack-years of smoking before the birth of their first child. We found no protective effect of smoking in post-menopausal age. The study contributed to the accumulating evidence for smoking - in particular in early life — as causally associated with an increased risk of breast cancer. All authors made substantial contributions to conception and design, analysis, and interpretation of data, and critical review of the manuscript.

ZJA contributed with an idea and design for the study, secured funding, and drafted the manuscript. JTJ performed the statistical analyses and contributed revising of the manuscript. EL helped with the design of the study and was involved in drafting the manuscript with respect to the literature review and interpretation of the results. EVB and RG have been involved in revising the manuscript critically for important intellectual content. All authors read and approved the final manuscript.

The study was entirely based on register data and was approved by the Danish Data Protection Agency — Danish law regarding ethical approval of register-based research does not require informed consent from study participants, thus no contact was made with the participating women or their relatives and general practitioners. Danish law regarding ethical approval of register-based research does not require consent from study participants to publish.

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Zorana Jovanovic Andersen, Email: kd. Elvira Vaclavik Brauner, Email: kd. Elsebeth Lynge, Email: kd. National Center for Biotechnology Information , U. BMC Cancer. Published online Aug Author information Article notes Copyright and License information Disclaimer.

Corresponding author. Received Jul 19; Accepted Aug This article has been cited by other articles in PMC. Abstract Background No scientific consensus has been reached on whether active tobacco smoking causes breast cancer.

Results Of 21, women mean age Conclusions Active smoking increases risk of breast cancer, with smoking before first birth being the most relevant exposure window. Keywords: Tobacco smoking, Active smoking, Breast cancer, Cohort. Background Tobacco smoke is the leading cause of cancer worldwide and contains over known carcinogenic substances. Breast cancer definition We linked the records of 28, nurses using unique identification number to the Danish Cancer Register [ 20 ] to extract all cancer diagnoses until Results Of the total 28, nurses in the Danish Nurse Cohort, we excluded 4 due to inactive emigrated vital status and with cancer diagnosis before cohort baseline, and with missing information on one or more covariates.

Open in a separate window. Table 3 Association between active smoking and breast cancer in 21, women in the Danish Nurse Cohort. N Person-years No.

Table 4 Effect modification of association between active smoking and breast cancer in 21, women in the Danish Nurse Cohort by menopausal status, obesity, alcohol consumption and hormone therapy use.

Overview of Cancer Latency Periods. An Expert Panel was convened by four Canadian agencies, the Ontario Tobacco Research Unit, the Public Health Agency of Canada, Physicians for a Smoke-Free Canada and the Canadian Partnership Against Cancer to comprehensively examine the weight of evidence from epidemiological and toxicological studies and understanding of biological mechanisms regarding the relationship between tobacco smoke and breast cancer. Multiethnic Cohort Study [5]. Although the association between active smoking and breast cancer is considerably weaker than that of many other smoking-related cancers 5 , the relationship is reasonably consistent in well-conducted cohort studies with long follow-up. No relationships were observed with other smoking parameters. Duration of solid fuel cookstove use is associated with increased risk of acute lower respiratory infection among children under six months in rural central India. Circulating sex hormones and breast cancer risk factors in postmenopausal women: reanalysis of 13 studies.

Active smoking increases breast cancer risk

Active smoking increases breast cancer risk. Risk Factors You Can Change

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Age of smoking initiation and risk of breast cancer in a sample of Ontario women

This summary table contains detailed information about research studies. Summary tables are a useful way to look at the science behind many breast cancer guidelines and recommendations. Learn how to read a research table. Introduction: Smoking increases the risk of many types of cancer including cancers of the lung, kidney and pancreas. Although findings on a possible link to breast cancer remain mixed, there's growing evidence smoking may slightly increase the risk of breast cancer.

More research is needed before solid conclusions can be made about a potential link between smoking and breast cancer. Some studies have shown smoking before having your first child may increase the risk of breast cancer []. Others have found no link between the two []. Find information on secondhand smoke exposure also called passive smoking and the risk of breast cancer.

Learn more about smoking and breast cancer risk. Learn about the strengths and weaknesses of different types of studies. See how this risk factor compares with other risk factors for breast cancer. Komen Perspectives. Therefore, some information may be out of date at this time. Study selection criteria: Prospective cohort studies with at least 1, breast cancer cases, pooled analyses and meta-analyses.

Table note: Relative risk above 1 indicates increased risk. Relative risk below 1 indicates decreased risk. Study Population number of participants. Follow-up years. Prospective cohort studies. Pooled and meta-analyses. Donate Now Fundraise. Smoking and breast cancer risk This summary table contains detailed information about research studies. Close X. EPIC [4]. Nurses' Health Study [8].

Bjerkaas et al. Canadian National Breast Screening Study [10]. Multiethnic Cohort Study [5]. California Teachers Study [12]. Iowa Women's Health Study [13]. Generations Study [7]. Black Women's Health Study [15]. Danish Nurse Cohort [16]. Norwegian-Swedish Cohort Study [17]. Nurses' Health Study II [18]. Gaudet et al. Macacu et al.

Active smoking increases breast cancer risk

Active smoking increases breast cancer risk