Diabetes and Endometrial Cancer in the Iowa Women’s Health Study

Diabetes and Endometrial Cancer in the Iowa Women’s Health Study1

Division of Epidemiology, University of Minnesota, Minneapolis, Minnesota 55454 [K. E. A., C. P. H., D. L., A. R. F.]; Department of Obstetrics and Gynecology, Medical School, University of Maryland, Baltimore, Maryland 21201 [E. A.]; Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, Maryland 20852 [P. J. M.]; Health and Behavior Studies, Teachers College, Columbia University, New York, New York 10027 [L. H. K.]; and Mayo Clinic, Rochester, Minnesota 55905 [T. A. S.]

Abstract

Diabetes has been associated with increased risk of endometrial cancer in some epidemiological studies. Body mass index (BMI) and other measures of obesity have been associated positively with both diabetes and endometrial cancer. It is not clear whether or not the association of diabetes with endometrial cancer is explained entirely by obesity. Thus, we sought to test the hypothesis that diabetes is not associated with endometrial cancer independent of obesity. We examined the association between self-reported diabetes (onset at >30 years of age) and incident endometrial cancer in a prospective cohort study of 24,664 postmenopausal women in Iowa. Over 12 years of follow-up, 346 cases occurred among the cohort at risk. Data were analyzed using proportional hazards regression models. Diabetes was analyzed as reported at baseline and as a time-dependent variable using information obtained during follow-up. After adjustment for BMI, waist:hip ratio, and other covariates, the relative risk (RR) for women with diabetes versus women without diabetes was 1.43 [95% confidence interval (CI), 0.98–2.1]. The diabetes association was confined to women in the upper two BMI quintiles (RR, 1.47; 95% CI, 0.98–2.20), but a formal test of interaction was not statistically significant. Analyses that included diabetes ascertained at baseline and at follow-up gave similar results; the diabetes-associated RR in the higher BMI strata was 1.64 (95% CI, 1.16–2.31). We conclude that after adjustment for other risk factors, diabetes is associated with a modestly increased risk for endometrial cancer among women in this cohort.

Footnotes

The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵1 Supported by National Cancer Institute Grant RO1 CA-39742.
↵2 To whom requests for reprints should be addressed, at Division of Epidemiology, University of Minnesota, 1300 South Second Street #300, Minneapolis, MN 55454.
↵3 P. J. M. was also supported by National Cancer Institute Training Grant T32CA09607 to Dr. Leslie Robison.
↵4 The abbreviations used are: BMI, body mass index; WHR, waist:hip ratio; HRT, hormone replacement therapy; IWHS, Iowa Women’s Health Study; OC, oral contraceptive; RR, relative risk; CI, confidence interval; SHBG, sex hormone-binding globulin; IGFBP-3, insulin-like growth factor-binding protein 3; IGF-I, insulin-like growth factor.
- Accepted March 23, 1901.
- Received August 2, 1900.
- Revision received March 14, 1901.