Smoking before the birth of a first child is not associated with increased risk of breast cancer: findings from the British Women's Heart and Health Cohort Study and a meta-analysis

Lawlor, Debbie A.; Ebrahim, Shah; Smith, George Davey

doi:10.1038/sj.bjc.6601916

Cited by 31 publications

(30 citation statements)

References 25 publications

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“…A metaanalysis based on 11 studies published before or in early 2004 concluded that smoking prior to a first birth is not associated with increased risk of breast cancer [26]. However, this meta-analysis did not include three recent cohort studies, all of which observed positive associations [15,18,24].…”

Section: Discussionmentioning

confidence: 97%

“…Among them, three of the case-controls studies [16,17,23] and all cohort studies [18,24,25] observed an increase in breast cancer risk with long-term cigarette smoking. In addition, two population-based case-control studies [16,17] and five cohort studies [15,18,[24][25][26] have assessed the association between smoking before a first full-term pregnancy and breast cancer risk. Among them, all of the case-control studies [16,17] and four of the cohort studies [15,18,24,25] associated smoking before a first full-term pregnancy with increased risk of breast cancer.…”

Section: Discussionmentioning

confidence: 99%

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Cigarette smoking and breast cancer risk: update of a prospective cohort study

Cui

Miller

Rohan

2006

Breast Cancer Res Treat

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The results of epidemiologic studies of the association between cigarette smoking and breast cancer risk have been inconsistent. In spite of the inconsistency, several recent analyses have suggested an increased risk of breast cancer among women who smoked cigarettes for a long period of time and/or who started smoking before their first pregnancy. Our analyses were conducted in the Canadian National Breast Screening Study (NBSS), a multi-center, randomized controlled trial of mammographic screening for breast cancer among 89,835 women aged 40-59 at enrollment. Participants were recruited between 1980 and 1985 from the general Canadian population. During an average of 16.1 years of follow-up, we identified 4,445 incident breast cancer cases. We used the Cox proportional hazards models to estimate multivariate rate ratios (RRs) and 95% confidence limits (CLs) for the association between cigarette smoking and breast cancer. We found that breast cancer risk was associated with the duration (40 years versus 0: RR = 1.50, 95% CL = 1.19, 1.89), intensity (40 cigarettes per day versus 0: RR = 1.20, 95% CL = 1.00, 1.44), cumulative exposure (40 pack-years versus 0: RR = 1.17, 95% CL = 1.02, 1.34), and latency of cigarette smoking (40 years since commencement of smoking versus 0: RR = 1.28, 95% CL = 1.06, 1.55), as well as smoking initiation before a first full-term pregnancy (among parous women, more than 5 years of smoking versus 0: RR = 1.13, 95% CL = 1.01-1.25). These results strongly suggest that cigarette smoking might play an important role in the etiology of breast cancer, particularly when initiated relatively early in life and when engaged in for long durations.

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Section: Discussionmentioning

confidence: 97%

Section: Discussionmentioning

confidence: 99%

Cigarette smoking and breast cancer risk: update of a prospective cohort study

Cui

Miller

Rohan

2006

Breast Cancer Res Treat

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“…There are many published reports on the effects of smoking on breast cancer risk in the general population [12][13][14][15][16][17][18][19][20][21][22]. In 2002, Terry and Rohan [23] reviewed the published studies and concluded that smoking probably did not increase the risk of breast cancer, although there may be an increased risk for women with a long duration of exposure and in those who smoked prior to a first full-term pregnancy.…”

Section: Discussionmentioning

confidence: 99%

Smoking and the risk of breast cancer in BRCA1 and BRCA2 carriers: an update

Ginsburg

Ghadirian

Lubiński

et al. 2008

Breast Cancer Res Treat

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Among women with a mutation in BRCA1 or BRCA2, the risk of breast cancer is high, but it may be modified by exogenous and endogenous factors. There is concern that exposure to carcinogens in cigarette smoke may increase the risk of cancer in mutation carriers. We conducted a matched case-control study of 2,538 cases of breast cancer among women with a BRCA1 (n = 1,920) or a BRCA2 (n = 618) mutation. One non-affected mutation carrier control was selected for each case, matched on mutation, country of birth, and year of birth. Odds ratios were calculated using conditional logistic regression, adjusted for oral contraceptive use and parity. Ever-smoking was not associated with an increased breast cancer risk among BRCA1 carriers (OR = 1.09; 95% CI 0.95-1.24) or among BRCA2 carriers (OR = 0.81; 95% CI 0.63-1.05). The result did not differ when cases were restricted to women who completed the questionnaire within two years of diagnosis. A modest, but significant increase in risk was seen among BRCA1 carriers with a past history of smoking (OR = 1.27; 95% CI 1.06-1.50), but not among current smokers (OR = 0.95; 0.81-1.12). There appears to be no increase in the risk of breast cancer associated with current smoking in BRCA1 or BRCA2 carriers. There is a possibility of an increased risk of breast cancer among BRCA1 carriers associated with past smoking. There may be different effects of carcinogens in BRCA mutation carriers, depending upon the timing of exposure.

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“…Corroborating these lines of reasoning, Band et al (2002) reported an increased risk with smoking initiated prior to first birth and among nulliparous women. However, a recent meta-analysis showed a null association between smoking prior to the birth of a first child and risk of breast cancer (Lawlor et al, 2004).…”

Section: Smoking and Breast Cancer Risk C Magnusson Et Almentioning

confidence: 99%

“…The role of smoking in breast cancer aetiology has been extensively studied (Band et al, 2002; Collaborative Group on Hormonal Factors in Breast Cancer, 2002;Terry and Rohan, 2002;Lawlor et al, 2004). Yet, the association remains equivocal and much debated (Terry and Rohan, 2002;Johnson, 2005).…”

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confidence: 99%

Cigarette smoking and breast cancer risk: a population-based study in Sweden

2007

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In a Swedish population-based case -control study, smoking showed no convincing association with risk of postmenopausal breast cancer -regardless of timing or level of smoking exposure -either overall or among subgroups. The role of smoking in breast cancer aetiology has been extensively studied (Band et al, 2002; Collaborative Group on Hormonal Factors in Breast Cancer, 2002;Terry and Rohan, 2002;Lawlor et al, 2004). Yet, the association remains equivocal and much debated (Terry and Rohan, 2002;Johnson, 2005). Smoking has been proposed to increase breast cancer risk, based on studies showing breast epithelial genotoxicity of tobacco-related compounds (Morabia, 2002), but also to exert an 'anti-oestrogenic effect' and thence to reduce risk (Terry and Rohan, 2002).We present results from a large population-based study, on the associations between the hypothesised 'carcinogenetic mode' of smoking, that is smoking prior to first birth or among nulliparous women, vs the 'anti-oestrogenic mode', that is recent smoking and risk of breast cancer. MATERIALS AND METHODS Study populationWe conducted a case -control study of breast cancer among all Swedish-born women aged 50 -74 years, in Sweden between October 1993 and March 1995.Cases were women with an incident invasive breast cancer, identified through the six Regional Cancer Registries. Out of 3979 eligible cases, 3345 (84%) participated. Controls were agefrequency matched according to the age distribution of cases, and randomly selected from the study population, using the Registry of the Total Population. Of the 4188 eligible controls, 3454 (82%) participated in the study. Data collectionStudy participants completed a postal questionnaire on average 4 months after diagnosis. Participants were asked in detail about their life-course smoking history and about other established breast cancer risk factors. Telephone interviews were conducted among controls who declined completion of the postal questionnaires. Out of all participating controls, 14% contributed information in this manner. Classification of smoking historyWomen were defined as ever smokers if they had smoked a total of at least 100 cigarettes, or if they had smoked regularly for at least 1 year. Women were attributed a 10-year duration of smoking for each 10-year age period they reported to be smokers, if they smoked during age-periods before and after. If not, they were attributed a duration of 5 years for each 10-year age period they reported to be smokers. Lifetime pack-years was calculated as the average smoking intensity multiplied by the estimated smoking duration. Statistical analysesRelative risks were estimated using unconditional logistic regression, adjusted for age in 5-year categories, yielding odds ratios (ORs) and 95% confidence intervals (CIs). Possible confounders were included as covariates in age-adjusted models one at a time and included in the final models if they affected parameter estimates more than 10%. The tested covariates were age at first birth, body mass index, socioeconomic ...

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Smoking before the birth of a first child is not associated with increased risk of breast cancer: findings from the British Women's Heart and Health Cohort Study and a meta-analysis

Cited by 31 publications

References 25 publications

Cigarette smoking and breast cancer risk: update of a prospective cohort study

Cigarette smoking and breast cancer risk: update of a prospective cohort study

Smoking and the risk of breast cancer in BRCA1 and BRCA2 carriers: an update

Cigarette smoking and breast cancer risk: a population-based study in Sweden

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