Letters Section Editor: Robert M. Golub, MD, Senior Editor.
In Reply: Dr Vachon suggests that possible differences in socioeconomic status or race might explain a reduced risk of colorectal cancer among aspirin users. However, the likelihood for such confounding is low in an occupationally homogeneous cohort such as the Nurses' Health Study. In addition, the percentage of nonwhite women in the cohort was low across all aspirin groups (1%-3%) and, thus, could not explain the magnitude of our associations. In analyses restricted to white women, our results were not materially different. Compared with women who denied any aspirin use, the multivariate relative risks for cancer were 1.08 (95% confidence interval [CI], 0.89-1.33) for women who used 0.5 to 1.5 standard aspirin per week, 0.83 (95% CI, 0.66-1.05) for 2 to 5 aspirin per week, 0.71 (95% CI, 0.55-0.92) for 6 to 14 aspirin per week, and 0.64 (95% CI, 0.43-0.94) for more than 14 aspirin per week (P for trend <.001). Others have confirmed a similar benefit of aspirin among African American persons.1 Furthermore, socioeconomic status did not appear to influence our previous observations that estrogen use is associated with a reduced risk of colorectal cancer.2 This result was later confirmed by a placebo-controlled randomized trial.3
Chan AT, Fuchs CS. Long-term Use of Aspirin and Risk of Colorectal Cancer—Reply. JAMA. 2005;294(24):3090-3091. doi:10.1001/jama.294.24.3090-c