Increased blood glucose and insulin, body size, and incident colorectal cancer

Background: Abdominal obesity-an elevated level of visceral adipose tissue- has been linked to colorectal cancer. Furthermore, elevated levels of visce ral adipose tissue have been associated with hyperinsulinemia, and insulin is a growth factor in the colon. We assessed whether waist circumference, a surrogate measure of visceral adipose tissue, and metabolic parameters ass ociated with visceral adipose tissue were related to colorectal cancer, Met hods: In the Cardiovascular Health Study cohort, we examined the relationsh ip of baseline measurements of body size, glucose, insulin, and lipoprotein s to incident colorectal cancer. All P values are two-sided. Results: Among 5849 participants, 102 incident cases of colorectal cancer were identified . Individuals in the highest quartile of fasting glucose had a nearly twofo ld increased risk of colorectal cancer (relative risk [RR] = 1.8; 95% confi dence interval [CI] = 1.0-3.1), and the linear trend RR (LT RR = 1.2; 95% C I = 1.0-1.5) for fasting glucose level was statistically significant (P =.0 2), Glucose and insulin levels 2 hours after oral glucose challenge also ex hibited statistically significant associations with colorectal cancer (2-ho ur glucose levels: RR = 2.4 [95% CI = 1.2-4.7]/LT RR = 1.3 [95% CI = 1.0-1. 6; P =.02]; 2-hour insulin levels: RR = 2.0 [95% CI = 1.0-3.8]/LT RR = 1.2 [95% CI = 1.0-1.5; P =.04]), Analysis of fasting insulin levels suggested a threshold effect, with values above the median associated with colorectal cancer (RR = 1.6; 95% CI = 1.1-2.4; P =.02). Higher levels of waist circumf erence were also statistically significantly associated with colorectal can cer (RR = 1.9; 95% CI = 1.1-3.3; P =.02). Conclusions: These data provide, to our knowledge, the first direct evidence of an association between eleva ted visceral adipose tissue level, its associated metabolic effects, and co lorectal cancer.