CHICAGO, Sept 25 (Reuters) - Patients showing signs of heart disease are at nearly double the risk of also having colon cancer, perhaps because unhealthy habits and inflammation are at the root of both, researchers said on Tuesday.

The association between heart disease, the single leading cause of death in industrialized countries, and the second most common type of cancer was confirmed in a study of more than 600 patients evaluated at the University of Hong Kong.

Previous studies have noted the increased likelihood of heart disease and colon cancer in the same patients, the study said. The two illnesses share several risk factors: smoking, high-fat diet, obesity, diabetes, high blood pressure, and sedentary lifestyle.

"Both colorectal (tumors) and (coronary artery disease) probably develop through the mechanism of chronic inflammation," study author Dr. Annie On On Chan of the University of Hong Kong wrote in the Journal of the American Medical Association.

In the study, of patients whose examinations showed at least a 50 percent narrowing of one of the coronary arteries feeding the heart, 34 percent also had cancerous colon tumors. That compared to some 20 percent of patients found to have tumors who were free of heart disease.

The family of cholesterol-lowering drugs called statins appear to have a deterrent effect on both illnesses, perhaps because the drugs reduce inflammation. Aspirin also seems to reduce the risk, the study said.

There were 1 million new colon cancer cases in 2002 globally, and 500,000 deaths that year from the disease, which is the most common type of malignancy after lung cancer.

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