Recent research has indicated that aspirin could decrease overall mortality by decreasing deaths from cancer, rather than from cardiovascular disease. In fact, advances in the treatment of cardiovascular disease might have eclipsed the benefits of aspirin.

One study suggested that taking aspirin daily for about 5 years could decrease digestive cancers by 40%, which would lead to a 16% reduction in the rate of overall cancer mortality (J Nat. Cancer Inst. 2012;104:1208-1217). When that study was published, experts did not recommend aspirin for cancer prevention because of the risk for serious gastrointestinal bleeding, stomach ulcers, and stroke.

In their review, the researchers examined data from recent systematic reviews and individual studies on the effect of aspirin on major digestive tract cancers, and on cancers of the breast, prostate, and lung.

Results suggest that over 10 years, about 33 to 127 people would need to take aspirin to prevent 1 major event, and 46 to 213 people would need to take aspirin to prevent death. Reductions in cancer would account for 61% to 80% of the benefit of aspirin use, and 30% to 60% of this would come from reductions in colorectal cancer.

The evidence for the reduction in incidence and death from colorectal cancer with aspirin use is “overwhelming”, according the researchers.

They found a 30% to 35% decreased risk of developing colorectal cancer with aspirin use, and a 35% to 40% decreased risk of dying from this cancer. They also found a 25% to 30% decreased risk of developing and a 45% to 50% decreased risk of dying from oesophageal cancer and a 25% to 30% decreased risk of developing and a 35% to 40% decreased risk of dying from stomach cancer. Smaller effects were found for breast, prostate, and lung cancer.

The benefits of taking aspirin appeared around 3 years after starting use. Death rates started to decrease after 5 years, and daily doses from 75 to 100 mg were linked to beneficial effects.

The most serious harm with aspirin use was stroke, which was rare but was linked to a 21% increased risk for mortality. Bleeding outside the brain was more common. Chronic aspirin use was linked to a 60% to 70% increase in the risk of dying from digestive tract bleeding. The rates of developing and dying from digestive tract complications were low for those younger than 70 years, but increased “steeply” for those older than 70.

Published online August 6, 2014. Abstract