Higher doses of aspirin needed to reduce risk of colorectal adenoma
Taking aspirin over the short- or long-term can reduce the risk for colorectal adenoma by 25 per cent, say researchers, but the greatest protective effect is seen at substantially higher doses than those currently recommended for the prevention of cardiovascular disease.
A cohort of women enrolled in the US nurses’ health study and who
underwent lower endoscopy between 1980 and 1998 was studied for self-reported
aspirin intake and incidence of colorectal adenoma. Of the 27,077 women
considered to be at average risk, 1,368 cases of adenoma of the distal
colon and rectum were confirmed.
The researchers found that compared with non-regular aspirin users, regular
users, defined as those taking two or more tablets per week had a lower
risk for distal colorectal adenoma (relative risk 0.75, 95 per cent confidence
interval 0.66–0.84).
This apparent benefit was substantially greater with increasing dose
of aspirin. Women who took the equivalent of 0.5 to 1.5 standard aspirin
tablets per week had a relative risk of 0.8 (CI 0.70–0.93), whereas
women who used more than 14 tablets per week had a relative risk of 0.49
(CI 0.36–0.65). This dose relationship was found to be significant
for both regular short-term users (<=5 years) and long-term users
(>5 years). Increasing the duration of aspirin use was not found to
reduce the risk.
The researchers say that these findings may have clinical implications
related to potential adverse effects associated with prolonged use of
aspirin. They suggest that thorough evaluation of the risks and benefits
of routine aspirin use at doses not previously considered is needed before
aspirin can be recommended for chemoprevention in the general adult population
(Annals of Internal Medicine 2004;140:157). |
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Pharmaceutical Journal