Epidemiology

BJC Open article

British Journal of Cancer (2012) 106, 227–232. doi:10.1038/bjc.2011.512 www.bjcancer.com
Published online 29 November 2011

A longitudinal study of serum insulin and glucose levels in relation to colorectal cancer risk among postmenopausal women

G C Kabat1, M Y Kim1, H D Strickler1, J M Shikany2, D Lane3, J Luo4, Y Ning5, M J Gunter6 and T E Rohan1

  1. 1Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, NY 10461, USA
  2. 2Division of Preventive Medicine, Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
  3. 3Department of Preventive Medicine, Stony Brook University Medical Center, Stony Brook, NY 11794, USA
  4. 4Department of Community Medicine, School of Medicine, West Virginia University, Morgantown, WV 26506, USA
  5. 5Department of Epidemiology and Community Health, School of Medicine, Virginia Commonwealth University Medical Center, Richmond, VA 23298, USA
  6. 6Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, Norfolk Place, London W2 1PG, UK

Correspondence: Dr GC Kabat, E-mail: geoffrey.kabat@einstein.yu.edu

Received 21 September 2011; Revised 25 October 2011; Accepted 29 October 2011
Advance online publication 29 November 2011

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Abstract

Background:

  

It is unclear whether circulating insulin or glucose levels are associated with increased risk of colorectal cancer. Few prospective studies have examined this question, and only one study had repeated measurements.

Methods:

  

We conducted a prospective study of colorectal cancer risk using the subsample of women in the Women's Health Initiative study whose fasting blood samples, collected at baseline and during follow-up, were analysed for insulin and glucose. Cox proportional hazards models were used to assess associations with colorectal cancer risk in both baseline and time-dependent covariates analyses.

Results:

  

Among 4902 non-diabetic women with baseline fasting serum insulin and glucose values, 81 incident cases of colorectal cancer were identified over 12 years of follow-up. Baseline glucose levels were positively associated with colorectal cancer and colon cancer risk: multivariable-adjusted hazard ratio (HR) comparing the highest (greater than or equal to99.5mgdl−1) with the lowest tertile (<89.5mgdl−1): 1.74, 95% confidence interval (CI) 0.97–3.15 and 2.25, 95% CI: 1.12–4.51, respectively. Serum insulin and homeostasis model assessment were not associated with risk. Analyses of repeated measurements supported the baseline results.

Conclusion:

  

These data suggest that elevated serum glucose levels may be a risk factor for colorectal cancer in postmenopausal women.

Keywords:

serum insulin; glucose; homeostasis model assessment-insulin resistance; colorectal cancer