Colorectal cancer associated with BMI, physical activity, diabetes, and blood glucose

Background: A sedentary lifestyle, obesity, and a Westernised diet have been implicated in the aetiology of both colorectal cancer and non-insulin dependent diabetes mellitus, leading to the hypothesis that insulin may promote colorectal cancer. We examined the association between colorectal cancer risk and body mass index (BMI), physical activity, diabetes mellitus, and blood glucose, in a cohort of 36,975 men and 38,244 women aged 20 years and more. Methods: The study cohort was established between 1984 and 1986, when almost 90% of the total adult population in the county of Nord-Trøndelag, Norway, participated in a large health screening survey. Information on incident colorectal cancer during 12 years follow-up was available from the Norwegian Cancer Registry. We used Cox regression to estimate multivariable adjusted relative risks (RRs) of colorectal cancer with 95% confidence intervals (CIs). P-values for trend was calculated by treating the exposure categories as an ordinal variable in the Cox model. Results: During 751,922 person-years a total of 730 cases of colorectal cancer were registered (368 in men and 362 in women). We found that the most physically active men had half the risk of colorectal cancer compared to the least physically active (Table 1). Among women, we found no significant association with physical activity, but an increased risk of colorectal cancer was observed among women with a history of diabetes. Also, women with non-fasting blood glucose ³8.0 mmol/L had twice the risk of colorectal cancer compared to women with glucose