Zhang, XuehongSmith-Warner, StephanieChan, AndrewWu, KanaSpiegelman, DonnaFuchs, CharlesWillett, WalterGiovannucci, Edward2019-09-212011Zhang, X., S. A. Smith-Warner, A. T. Chan, K. Wu, D. Spiegelman, C. S. Fuchs, W. C. Willett, and E. L. Giovannucci. 2011. “Aspirin Use, Body Mass Index, Physical Activity, Plasma C-Peptide, and Colon Cancer Risk in US Health Professionals.” American Journal of Epidemiology 174 (4): 459–67. https://doi.org/10.1093/aje/kwr115.0002-92621476-6256http://nrs.harvard.edu/urn-3:HUL.InstRepos:41384715Aspirin use decreases colon cancer risk, but this association may vary among population subgroups. The aspirin-colon cancer association was evaluated according to body mass index and physical activity in 1,701 incident colon cancer cases diagnosed during follow-up of 139,310 participants for up to 26 years in 2 US prospective cohort studies that began in 1980 and 1992, respectively. Whether plasma C-peptide levels modified the association was examined by using a nested case-control design (n = 384 cases, 749 controls). Multiplicative and additive interactions were tested. Body mass index did not modify the association; pooled multivariable relative risks for regular aspirin use versus nonuse ranged from 0.74 to 0.75 in the normal weight and obese groups (test for multiplicative interaction, P = 0.75; test for additive interaction, P = 0.66). Pooled multivariable relative risks for regular aspirin use were 0.86 (95% confidence interval (CI): 0.66, 1.11) in the low and 0.67 (95% CI: 0.58, 0.77) in the high physical activity groups with no interaction evident on either the multiplicative or additive scale (P > 0.10). Plasma C-peptide levels also did not modify the aspirin-colon cancer association, with multivariable relative risks of 0.74 (95% CI: 0.50, 1.10) for the low and 0.65 (95% CI: 0.46, 0.92) for the high group. Reductions in colon cancer risk associated with aspirin use were not significantly modified by body mass index, physical activity, or plasma C-peptide level in this study.en-USJournal Article2019-09-2110.1093/aje/kwr115