Two research studies report on the benefits and risks of colonoscopy in adults over age 80.

Colonoscopy is considered the gold standard for finding and removing -- and possibly preventing -- colorectal cancer. It can detect up to 95% of colon cancers and can be used to remove precancerous polyps before they develop into cancer.

Now new research shows that after age 80, colonoscopies are of limited value. According to two studies reported in the Journal of the American Medical Association (JAMA ) (Volume 295, page 2357 ) and the Journal of Diseases of the Colon and Rectum (Volume 49, page 646 ) colonoscopy after the age of 80 may not be worth the risk of complications.

These studies are the first to address the issue of when people might stop colonoscopy screenings, which are recommended every 10 years. Altogether, they reviewed results from more than 2,000 patients.

Though the risks of developing colon cancer increase with age, life expectancy decreases after age 80. Since cancer-prone polyps (adenomas) grow slowly, older people are more likely than younger ones to die of other causes before a polyp turns cancerous, researchers noted.

In one study that reviewed colonoscopy in people ages 50 to over 80, screening in the very elderly resulted in only 15% of the expected gain in life expectancy of younger persons. Researchers also noted an increase in incomplete exams, inadequate bowel preparation, and complications in elderly patients. The colonoscopy is safe for the elderly, its limited value suggests that risks and patient preferences should be considered, wrote the researchers in JAMA. Those writing in the Journal of Diseases of the Colon and Rectum recommend limiting colonoscopy in the elderly to patients with symptoms or specific clinical indications.