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BishopCancer Research UKAichi Cancer Center Hospital and Research InstituteAlbert Einstein College of Medicine of Yeshiva UniversityAmerican Cancer SocietyEmory UniversityIRCCS Centro Di Riferimento Oncologico AvianoMahidol UniversityJohns Hopkins UniversityUniversity of QueenslandBritish Columbia Cancer AgencyUniversity of Hawaii SystemCanadian Cancer Registries Epidemiology Research GroupCatalan Oncology InstituteCenters for Disease Control and PreventionMax Delbruck Center for Molecular MedicineUniversity of MelbourneBrigham and Women's HospitalCancer Institute IndiaChiang Mai UniversityChulalongkorn UniversityKraeftens BekaempelseKarolinska InstitutetGerman Cancer Research CenterUniversity of OtagoIstituto Europeo di OncologiaFred Hutchinson Cancer Research CenterInsermGirona Cancer RegistryHospital General de MexicoHospital UniversitarioIcelandic Cancer SocietyInstitut de Cancerologie Gustave RoussyLondon School of Hygiene &amp; Tropical MedicineInternational Agency for Research on CancerChaim Sheba Medical Center IsraelKaiser PermanenteInstitut Universitaire de Medecine Sociale et Preventive LausanneOnkoloski institut LjubljanaLoma Linda University Adventist Health Sciences CenterSkånes universitetssjukhusMaastricht UniversityUniversity of the Philippines ManilaIstituto di Ricerche Farmacologiche Mario NegriFondazione IRCCS Istituto Nazionale dei Tumori, MilanIstituto di Statistica Medica e BiometriaNairobi Centre for Research in ReproductionNational Cancer InstituteNational Institute of Child Health and Human DevelopmentNational University of SingaporeThe Netherlands Cancer InstituteNEW JERSEY STATE DEPT OF HEALTHNew South Wales Cancer CouncilColumbia University Medical CenterOntario Cancer Treatment and Research FoundationClinical Trial Service UnitRadiation Effects Research Foundation HiroshimaRoyal College of General Practitioners' Oral Contraception StudyUniversidad de Costa RicaMedical Center of Fudan UniversityShanghai Institute of Planned Parenthood ResearchTianjin Cancer Institute and HospitalUniversitetet i TromsoVanderbilt UniversityUniversity of Athens Medical SchoolUniversidad de ChileUniversity of EdinburghUniversity of Minnesota School of Public HealthThe University of North Carolina at Chapel HillUniversity of NottinghamUniversity of Southern CaliforniaUniversity of WisconsinOrganisation Mondiale de la Sante2018-07-242018-07-242002-11-18British Journal of Cancer. Vol.87, No.11 (2002), 1234-1245000709202-s2.0-0037132383https://repository.li.mahidol.ac.th/handle/20.500.14594/20027Alcohol and tobacco consumption are closely correlated and published results on their association with breast cancer have not always allowed adequately for confounding between these exposures. Over 80% of the relevant information worldwide on alcohol and tobacco consumption and breast cancer were collated, checked and analysed centrally. Analyses included 58 515 women with invasive breast cancer and 95 067 controls from 53 studies. Relative risks of breast cancer were estimated, after stratifying by study, age, parity and, where appropriate, women's age when their first child was born and consumption of alcohol and tobacco. The average consumption of alcohol reported by controls from developed countries was 6.0 g per day, i.e. about half a unit/drink of alcohol per day, and was greater in ever-smokers than never-smokers, (8.4 g per day and 5.0 g per day, respectively). Compared with women who reported drinking no alcohol, the relative risk of breast cancer was 1.32 (1.19-1.45, P<0.00001) for an intake of 35-44 g per day alcohol, and 1.46 (1.33-1.61, P<0.00001) for ≥45 g per day alcohol. The relative risk of breast cancer increased by 7.1% (95% Cl 5.5-8.7%; P<0.00001) for each additional 10 g per day intake of alcohol, i.e. for each extra unit or drink of alcohol consumed on a daily basis. This increase was the same in ever-smokers and never-smokers (7.1% per 10 g per day, P<0.00001, in each group). By contrast, the relationship between smoking and breast cancer was substantially confounded by the effect of alcohol. When analyses were restricted to 22255 women with breast cancer and 40832 controls who reported drinking no alcohol, smoking was not associated with breast cancer (compared to never-smokers, relative risk for ever-smokers=1.03, 95% Cl 0.98-1.07, and for current smokers=0.99, 0.92-1.05). The results for alcohol and for tobacco did not vary substantially across studies, study designs, or according to 15 personal characteristics of the women; nor were the findings materially confounded by any of these factors. If the observed relationship for alcohol is causal, these results suggest that about 4% of the breast cancers in developed countries are attributable to alcohol. In developing countries, where alcohol consumption among controls averaged only 0.4 g per day, alcohol would have a negligible effect on the incidence of breast cancer. In conclusion, smoking has littte or no independent effect on the risk of developing breast cancer; the effect of alcohol on breast cancer needs to be interpreted in the context of its beneficial effects, in moderation, on cardiovascular disease and its harmful effects on cirrhosis and cancers of the mouth, larynx, oesophagus and liver. © 2002 Cancer Research UK.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyMedicineArticleSCOPUS10.1038/sj.bjc.6600596