To the editor:
García Rodríguez et al. 1 conducted a population-based cohort study with a secondary case-control analysis. The study was unique in analyzing the effects of dose and duration of nonsteroidal antiinflammatory drug (NSAID) use, particularly aspirin, and its protective effect against colorectal cancer. However, we have two observations: one regarding possible bias and the other concerning the implications of their conclusions.
People may be prescribed aspirin because they are at high risk for cardiovascular disease, and therefore have a higher mortality rate. Aspirin takers may have died early due to myocardial infarction or cerebrovascular accident prior to development of colorectal cancer and the reported lower incidence of colorectal cancer among aspirin takers may be due to competing causes of mortality rather than to any protective effect of aspirin. The authors do not report causes of death or death rates for study participants, which would resolve this The study states that in a population of 1,000, NSAID treatment for 1 year would prevent one case of colorectal cancer in the age range 70–79.
Holvoet et al. 2 state that 30% of gastrointestinal hemorrhage is attributable to NSAIDs. With an incidence of 5.5 per 1,000 (in the same age group), 3 we would expect about two extra cases of gastrointestinal bleeding in 1,000 people taking NSAIDs. We therefore wonder if the reported benefit might be outweighed by the risk of gastrointestinal hemorrhage and other complications associated with such doses of NSAID.
1. García Rodríguez LA, Huerta-Alvarez C. Reduced risk of colorectal cancer among long-term users of aspirin and nonaspirin nonsteroidal antiinflammatory drugs. Epidemiology 2001; 12:88–93.
2. Holvoet J, Terriere L, Van Hee W, Verbist L, Fierens E, Hautekeete ML. Relation of upper gastrointestinal bleeding to nonsteroidal antiinflammatory drugs and aspirin: a case-control study. Gut 1991; 32:730–734.
3. Longstreth GF. Epidemiology of hospitalisation for acute upper gastrointestinal haemorrhage: a population-based study. Am J Gastroenterol 1995; 90:206–210.