title: Metabolic syndrome and breast cancer risk: a case-cohort study nested in a multicentre italian cohort.
abstract: BACKGROUND
  Metabolic syndrome (defined as at least three among abdominal obesity, high blood triglycerides, low high-density lipoprotein cholesterol, high blood glucose, and high blood pressure) is emerging as a risk factor for breast cancer; however few studies - most confined to postmenopausal women - have investigated associations between breast cancer risk and metabolic syndrome. The purpose of this study was to examine the association between metabolic syndrome and its components, and risk of breast cancer in postmenopausal and premenopausal women.
  
  
  METHODS
  We performed a case-cohort study on 22,494 women recruited in 1993-1998 to four Italian centres (Turin, Varese, Naples, Ragusa) of the European Prospective Investigation into Cancer and Nutrition (EPIC) and followed-up for up to 15 years. A random subcohort of 565 women was obtained and 593 breast cancer cases were diagnosed. Hazard ratios (HR) with 95% confidence intervals (CI), adjusted for potential confounders, were estimated by Prentice-weighted Cox proportional hazards models.
  
  
  RESULTS
  Presence of metabolic syndrome was associated with significantly increased breast cancer risk in all women (HR 1.52, 95%CI 1.14-2.02). When the analyses were repeated separately for menopausal status, the association was limited to postmenopausal women (HR 1.80, 95%CI 1.22-2.65) and absent in premenopausal women (HR 0.71, 95%CI 0.43-1.16); P for interaction between metabolic syndrome and menopausal status was 0.001. Of metabolic syndrome components, only high blood glucose was significantly associated with increased breast cancer risk in all women (HR 1.47, 95%CI 1.13-1.91) and postmenopausal women (HR 1.89, 95%CI 1.29-2.77), but not premenopausal women (HR 0.80, 95%CI 0.52-1.22; P interaction=0.004).
  
  
  CONCLUSIONS
  These findings support previous data indicating that metabolic syndrome is an important risk factor for breast cancer in postmenopausal women, but not in premenopausal women, and suggest that prevention of metabolic syndrome through lifestyle changes could confer protection against breast cancer.
authors.affiliation: Epidemiology and Prevention Unit, Fondazione IRCCS - Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Agnoli
authors.affiliation: Epidemiology and Prevention Unit, Fondazione IRCCS - Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Grioni
authors.affiliation: Epidemiology and Prevention Unit, Fondazione IRCCS - Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Sabina
authors.initials: S
authors.lastname: Sieri
authors.affiliation: Human Genetics Foundation, Turin, Italy; Piemonte Centre for Cancer Prevention, Turin, Italy.
authors.forename: Carlotta
authors.initials: C
authors.lastname: Sacerdote
authors.affiliation: Human Genetics Foundation, Turin, Italy; Piemonte Centre for Cancer Prevention, Turin, Italy.
authors.forename: Fulvio
authors.initials: F
authors.lastname: Ricceri
authors.affiliation: Cancer Registry, ASP 7 Ragusa, Italy.
authors.forename: Rosario
authors.initials: R
authors.lastname: Tumino
authors.affiliation: Cancer Registry, ASP 7 Ragusa, Italy.
authors.forename: Graziella
authors.initials: G
authors.lastname: Frasca
authors.affiliation: Epidemiology and Prevention Unit, Fondazione IRCCS - Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Pala
authors.affiliation: Department of Clinical and Experimental Medicine, University of Naples Federico II, Naples, Italy.
authors.forename: Amalia
authors.initials: A
authors.lastname: Mattiello
authors.affiliation: Department of Mental and Physical Health and Preventive Medicine, Second University of Naples, Naples, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Chiodini
authors.affiliation: Laboratory of Molecular and Nutritional Epidemiology, Department of Epidemiology and prevention, IRCCS Istituto Neurologico Mediterraneo Neuromed, Pozzilli (IS), Italy.
authors.forename: Licia
authors.initials: L
authors.lastname: Iacoviello
authors.affiliation: Laboratory of Molecular and Nutritional Epidemiology, Department of Epidemiology and prevention, IRCCS Istituto Neurologico Mediterraneo Neuromed, Pozzilli (IS), Italy.
authors.forename: Amalia
authors.initials: A
authors.lastname: De Curtis
authors.affiliation: Department of Clinical and Experimental Medicine, University of Naples Federico II, Naples, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Panico
authors.affiliation: Epidemiology and Prevention Unit, Fondazione IRCCS - Istituto Nazionale dei Tumori, Milan, Italy.
authors.forename: Vittorio
authors.initials: V
authors.lastname: Krogh
mesh_terms: D001786:Blood Glucose / Q000502:physiology; D001943:Breast Neoplasms / Q000097:blood / Q000209:etiology*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications; D007558:Italy; D008019:Life Style; D024821:Metabolic Syndrome / Q000097:blood / Q000150:complications* / Q000378:metabolism; D017698:Postmenopause / Q000097:blood / Q000378:metabolism; D017697:Premenopause / Q000097:blood / Q000378:metabolism; D011446:Prospective Studies; D012307:Risk Factors; D044465:White People
chemical_list: D001786:Blood Glucose