Obesity is a risk factor for
colon cancer, possibly due to elevated levels of circulating
cytokines derived from adipose tissue.
Aspirin, which may affect the levels of these
cytokines, has been shown in randomized controlled trials to decrease the risk of colorectal
adenomas. We hypothesized that the chemopreventive effect of
aspirin might be greater in individuals with higher body mass index (BMI). Data were available from the
Aspirin/
Folate Polyp Prevention Study, a randomized controlled trial of
aspirin and
folic acid to prevent recurrent colorectal
adenomas.
Obesity was defined as BMI > or = 30 (kg/m2),
overweight as BMI of 25-29 (kg/m2) and normal weight as BMI <25 (kg/m2). For the analysis of the effect of
aspirin on the recurrence of colorectal
adenoma by BMI, we computed risk ratios for
aspirin versus placebo within the three BMI strata using a modified Poisson model. Overall the risk reduction of
adenomas with a daily dose of 325 mg
aspirin was greater among subjects with higher BMI. Among obese subjects the risk ratio (RR) for advanced
adenomas compared with placebo was 0.44 (95% CI 0.17-1.10), versus RR = 1.23 (95% CI 0.55-2.77) among those with normal weight. However, 81 mg
aspirin daily did not interact with BMI to modify the risk of
adenomas in such a fashion. The more pronounced effect of 325 mg
aspirin in individuals with higher BMI suggests a possible protective role of anti-inflammatory
aspirin against increased adipose-driven
cytokines among obese subjects.