WASHINGTON (REUTERS) - Former vice-president Joe Biden is healthy enough to undertake the duties of the US presidency, his doctor said on Tuesday (Dec 17) in a health report released by the Democrat's campaign.

Biden, 77, is one of 15 Democrats seeking their party's nomination to run against Republican US President Donald Trump next year in a battle in which the incumbent and the top three of his would-be opponents are all septuagenarians.

Biden, who suffered a brain aneurysm in 1988, has no symptoms of similar problems, and while his heart beats irregularly, he is "completely asymptomatic," said Dr Kevin O'Connor, who teaches medicine and directs the Executive Medicine programme for George Washington University Medical Faculty Associates.

The former vice-president is taking anticoagulant medication for his heart and Crestor for high cholesterol, O'Connor said.

He has had no cancer other than "localised, non-melanoma skin cancers," due to extended exposure to the sun as a younger man, nor any history of diabetes, thyroid disease, hypertension, angina or any neurologic disorder, the doctor's report said.

"Vice-president Biden is a healthy, vigorous, 77-year-old male, who is fit to successfully execute the duties of the presidency, to include those as Chief Executive, Head of State and Commander in Chief," O'Connor wrote.

O'Connor has been Biden's physician since 2009, when he was assigned as physician to the vice president, the report said.

One of Biden's closest rivals for the nomination, Senator Bernie Sanders, 78, suffered a heart attack earlier this fall but has since resumed campaigning.