LOS ANGELES — A daily dose of baby aspirin may reduce mortality from a range of common cancers by an average of 21 percent, and the reduction persisted for at least 20 years, British researchers reported Monday.

Deadly cases of stomach, colorectal and esophageal cancers all declined among people who took low-dose aspirin for 10 to 20 years, according to a study published online in the journal Lancet. The chewable tablets also were linked to a reduced risk of death from adenocarcinoma and from lung cancer in nonsmokers.

The results were based on an analysis of more than 10,000 people who participated in seven clinical trials designed to test whether baby aspirin could reduce the risk of heart disease.

“We already had strong evidence that low-dose aspirin could reduce deaths from colorectal cancer by as much as a third, but this provides important new evidence that long-term aspirin use can provide protection against a variety of other cancers,“ said epidemiologist Eric Jacobs of the American Cancer Society. However, he added, “it would be premature at this point to recommend that people start using aspirin specifically to prevent cancer.”

For the millions of people who are currently taking low doses of aspirin to protect against cardiovascular disease, “the findings suggest that they should have some additional benefit for cancer,” said Dr. Lori Minasian, who is in charge of large cancer prevention trials at the National Cancer Institute.

Most of the studies examined by the British researchers involved primarily men, but the team said that the fundamental mechanisms involved probably hold equally for women.

A variety of studies in animals show that salicylate, the active ingredient in aspirin, can suppress tumors. Observational data in the 1970s suggested that aspirin could suppress tumors in humans, but alternative explanations were offered and experts demanded randomized clinical trials.