title: Modelling body mass index and endometrial cancer risk in a pooled-analysis of three case-control studies.
abstract: OBJECTIVE
  To quantify the relation between body mass index (BMI) and endometrial cancer risk, and to describe the shape of such a relation.
  
  
  METHODS
  Pooled analysis of three hospital-based case-control studies.
  
  
  METHODS
  Italy and Switzerland.
  
  
  METHODS
  A total of 1449 women with endometrial cancer and 3811 controls.
  
  
  METHODS
  Multivariate odds ratios (OR) and 95% confidence intervals (95% CI) were obtained from logistic regression models. The shape of the relation was determined using a class of flexible regression models.
  
  
  METHODS
  The relation of BMI with endometrial cancer.
  
  
  RESULTS
  Compared with women with BMI 18.5 to <25 kg/m(2) , the odds ratio was 5.73 (95% CI 4.28-7.68) for women with a BMI ≥35 kg/m(2) . The odds ratios were 1.10 (95% CI 1.09-1.12) and 1.63 (95% CI 1.52-1.75) respectively for an increment of BMI of 1 and 5 units. The relation was stronger in never-users of oral contraceptives (OR 3.35, 95% CI 2.78-4.03, for BMI ≥30 versus <25 kg/m(2) ) than in users (OR 1.22, 95% CI 0.56-2.67), and in women with diabetes (OR 8.10, 95% CI 4.10-16.01, for BMI ≥30 versus <25 kg/m(2) ) than in those without diabetes (OR 2.95, 95% CI 2.44-3.56). The relation was best fitted by a cubic model, although after the exclusion of the 5% upper and lower tails, it was best fitted by a linear model.
  
  
  CONCLUSIONS
  The results of this study confirm a role of elevated BMI in the aetiology of endometrial cancer and suggest that the risk in obese women increases in a cubic nonlinear fashion. The relation was stronger in never-users of oral contraceptives and in women with diabetes.
authors.affiliation: Department of Epidemiology, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Rota
authors.affiliation: Department of Epidemiology, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Rumi
authors.affiliation: Department of Statistics and Quantitative Methods, University of Milan-Bicocca, Milan, Italy.|Division of Epidemiology and Biostatistics, European Institute of Oncology, Milan, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Bagnardi
authors.affiliation: Unit of Epidemiology and Biostatistics, CRO Aviano National Cancer Institute, IRCCS, Aviano, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Dal Maso
authors.affiliation: Unit of Epidemiology and Biostatistics, CRO Aviano National Cancer Institute, IRCCS, Aviano, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Zucchetto
authors.affiliation: Institute for Social and Preventive Medicine, University of Lausanne, Lausanne, Switzerland.
authors.forename: F
authors.initials: F
authors.lastname: Levi
authors.affiliation: Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy.
authors.forename: C
authors.initials: C
authors.lastname: La Vecchia
authors.affiliation: Department of Epidemiology, IRCCS-Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Tavani
mesh_terms: D015992:Body Mass Index; D016022:Case-Control Studies; D016889:Endometrial Neoplasms / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control; D005260:Female; D006801:Humans; D007558:Italy / Q000453:epidemiology; D016015:Logistic Models; D009765:Obesity / Q000150:complications* / Q000453:epidemiology / Q000517:prevention & control; D016017:Odds Ratio; D012307:Risk Factors; D013557:Switzerland / Q000453:epidemiology
keywords: Body mass index; endometrial cancer; fractional polynomial; hospital-based case-control studies; obesity; overweight