McCain, 72, a former smoker poised to become the Republican presidential nominee, has about a 20 percent of dying in office and a higher rate of disability, John Banzhaf, George Washington University professor, said Wednesday in a release.

Palin, 44, McCain's running mate, is governor in Alaska.

McCain's smoking history boosts his risk of dying from lung cancer by about 700 percent, and his risk of dying of chronic obstructive pulmonary disease also is greater, Banzhaf said. His age increases his odds of becoming disabled from conditions such as a stroke or Alzheimer's disease, which can impair judgment.

McCain has a 10-year death rate of between 35 percent and 50 percent, the professor said.

Potential health risks facing Democratic nominee Barack Obama, 47, are different, Banzhaf said. Men who are age 45 and are former smokers have less than a 5 percent chance of dying within the next 10 years, Banzhaf said. Even with an occasional lapse, Banzhaf said, Obama's 10-year death risk still is under 10 percent.

Obama's running mate, Sen. Joe Biden, D-Del., is 66.