Aspirin Use and Reduced Risk of Fatal Colon Cancer

TLDR

Animal experiments and two human epidemiologic studies suggest aspirin and other NSAIDs may protect against colon cancer, though the mechanism—direct prostaglandin inhibition or indirect factors—is unclear, and acetaminophen shows no such association. The study tested the hypothesis that aspirin use reduces colon cancer mortality in a prospective cohort of 662,424 adults. Death rates from colon cancer were measured through 1988, and multivariate analyses of 598 cases and 3058 matched controls examined other risk factors, revealing that more frequent aspirin use was associated with lower colon cancer mortality in both sexes. Regular low‑dose aspirin use was associated with a 40–42% reduction in fatal colon cancer risk (RR ≈ 0.60 in men, 0.58 in women), a finding robust to exclusion of participants with pre‑existing conditions and adjustment for diet, obesity, activity, and family history, while acetaminophen use showed no effect.

Abstract

Experiments in animals and two epidemiologic studies in humans suggest that aspirin and other nonsteroidal antiinflammatory drugs (NSAIDs) may be protective against colon cancer. We tested this hypothesis in a prospective mortality study of 662,424 adults who provided information in 1982 on the frequency and duration of their aspirin use. Death rates from colon cancer were measured through 1988. The possible influence of other risk factors for colon cancer was examined in multivariate analyses for 598 case patients and 3058 matched control subjects drawn from the cohort.Death rates from colon cancer decreased with more frequent aspirin use in both men and women. The relative risk among persons who used aspirin 16 or more times per month for at least one year was 0.60 in men (95 percent confidence interval, 0.40 to 0.89) and 0.58 in women (95 percent confidence interval, 0.37 to 0.90). The risk estimates were unaffected when we excluded persons who reported at entry into the study that they had cancer, heart disease, stroke, or another condition that might influence both their aspirin use and their mortality. Adjustment for dietary factors, obesity, physical activity, and family history did not alter the findings significantly. No association was found between the use of acetaminophen and the risk of colon cancer.Regular aspirin use at low doses may reduce the risk of fatal colon cancer. Whether this is due to a direct effect of aspirin, perhaps mediated by the inhibition of prostaglandin synthesis, or to other factors indirectly associated with aspirin use is unclear.