What's in a Number?

Prostate: The candidate has no sign of prostate cancer, although doctors noted a condition known as benign prostatic hypertrophy (an enlarged prostate). The condition is very common, affecting 80 percent of men his age, and does not forecast cancer. Effect: 0.

Kidney Stones: These could be a concern, but the fact that McCain takes only two mild medications to prevent further stones indicates that his doctors aren't worried about a serious underlying condition. Effect: 0.

Colon polyps: McCain had benign growths removed during a routine colonoscopy in March. Nothing cancerous was detected. Effect: 0.

Arthritis: McCain suffers from degenerative arthritis. Roizen says that would only affect McCain's Real Age if it interfered with his ability to exercise. (Information on McCain's exercise habits was unavailable.) Effect: 0.

Smoking: A former smoker, McCain kicked the habit in 1980. Effect: One year older.

Fitness: McCain makes much of having hiked the Grand Canyon "rim to rim" in 2006. Roizen is not impressed. "Physical fitness comes and goes in about three weeks," he says. "If McCain is not continually active, it doesn't mean much." Effect: Unclear (not enough information).

Monitoring His Health: The fact that McCain goes for regular checkups is an excellent sign. His most recent comprehensive exam was in March. Effect: 2 years younger.

Bottom line: 8.1 years younger, or 63.7 years old.

But the eventual winner of the election—no matter who it is—should be forewarned. Roizen has assessed data on presidential health back to the 1920s and finds that the stress of the job takes a toll. "Every year in office, you age two years," he says. It's not hard to calculate the effect this would have on McCain. After two terms, his calendar age and Real Age would be right back in line.

© 2008