Washington: Senator Bernie Sanders, I-Vt, who suffered a heart attack in October and is the oldest major candidate for president in 2020, released information from three of his doctors Monday saying that he sustained “modest heart muscle damage” but is in good health and capable of doing the job.

“At this point, I see no reason he cannot continue campaigning without limitation and, should he be elected, I am confident he has the mental and physical stamina to fully undertake the rigours of the presidency,” Martin LeWinter, attending cardiologist at the University of Vermont Medical Centre, wrote in a letter dated December 30.

The senator has made an “uneventful recovery” from his heart attack, LeWinter said, adding that Sanders has been taking several medications routinely prescribed after heart attacks. “While he did suffer modest heart muscle damage, he has been doing very well since,” LeWinter wrote.

LeWinter’s letter was one of three provided by the Sanders campaign, which had said it would release his health records by the end of the year. The letters are not raw medical data, but they contain specific information about his health.

Questions have surrounded Sanders’ health since he suffered a heart attack on Oct. 1 that was not immediately disclosed by his campaign, prompting his hospitalisation and the insertion of two stents, while forcing the candidate off the campaign trail for two weeks. The doctors’ letters Monday depicted an impressive recovery, but they are unlikely to entirely quell the questions about Sanders’ physical sturdiness as he seeks one of the toughest jobs in the world.

The most detailed letter comes from Brian Monahan, Congress’ attending physician, who said his office has been Sanders’ doctor for the past 29 years. “You are in good health currently and you have been engaging vigorously in the rigours of your campaign, travel, and other scheduled activities without any limitation,” wrote Monahan in a letter dated December 28.

Monahan wrote that Sanders’ most recent physical, conducted Dec. 19, showed that he was six feet tall and weighed 174 pounds. His general physical condition was normal, his blood pressure was 102/56, and his pulse rate was 62 beats per minute. His blood count, vitamin D level and thyroid function were normal, Monahan added.

The most notable event in Sanders’ health history was his recent heart attack, Monahan wrote, adding that an examination at the time showed “diminished heart muscle strength and chamber wall motion reduction.”

A segment of an artery that had become narrowed was reopened, then the stents were inserted, Monahan said. Sanders received several medications, including blood thinners and beta blockers, but some were discontinued as he made progress.

In addition, the senator underwent a successful treadmill exercise this month. “Mr. Sanders was able to exercise to a level that is approximately 50% higher than other men his age with a similar diagnosis,” said one of the letters. LeWinter added that Sanders is now “entirely asymptomatic.”

Asked if the campaign would make his doctors available for interviews or release more detailed records, Sanders campaign spokesman Mike Casca replied, “The letters are clear.”

The Washington Post asked Quinn Capers IV, an interventional cardiologist and professor of internal medicine at Ohio State University who has not participated in Sanders’ care, to review the letters. Capers said there were encouraging signs for the senator.

“In addition to the fact that his heart muscle strength has recovered, the most positive news for Mr. Sanders’ cardiac prognosis is the result of his stress test,” Capers said. “Taken together, these findings imply that with continued medication, follow-up and exercise, Mr. Sanders’ cardiac prognosis and outlook is very good.”

When he ran for president in 2016, Sanders released a letter from Monahan stating that he was in “very good health” and had a history of relatively minor medical procedures.

Sanders will be 79 on Inauguration Day in 2021. President Donald Trump, the oldest to take the office, is 73.

Sanders is not the only candidate to face questions about his age; three other Democratic contenders — former vice president Joe Biden, former New York mayor Mike Bloomberg and Sen. Elizabeth Warren, D-Mass. — are also septuagenarians. They have each previously released information about their health in recent weeks.

Warren provided a letter from her physician, with supporting medical records, describing her as “very healthy.” Biden put out a three-page summary of his medical history in which his doctor declared he is a “healthy, vigorous” 77-year-old fully capable of taking on the role of president. Bloomberg released a doctor’s letter that described him as a “77-year-old man in outstanding health.”

Sanders had his heart attack during a visit to Las Vegas. He was hospitalised after experiencing chest pains at a campaign event, but the Sanders campaign did not disclose that he had suffered a heart attack until Oct. 4, when he was discharged from the hospital. In the intervening days, aides declined to answer direct questions about whether he’d had a heart attack.

Asked at the time why the campaign did not provide that information sooner, Casca said, “We just wanted to wait until he was discharged to give out the information all at once.”

In the days immediately following his hospitalisation, there was some uncertainty inside the campaign about whether the presidential effort would continue. But Sanders emerged from his hiatus with surprising momentum, delivering a widely praised debate performance and winning endorsements from three young, liberal congresswomen who belong to a group known as the “Squad.” He now sits at or near the top of the polls in several early nominating states.

Sanders has maintained one of the busiest campaign schedules in the field, often sprinting between multiple events in a single day. While he has tempered his pace at times since the heart attack, he is still holding more events than many of his competitors.

The Sanders campaign has made efforts to showcase his robustness and highlight his physical activities, distributing images of the candidate shooting hoops on a basketball court or taking batting practice on a baseball diamond.

As he campaigned in November, he appeared more relaxed on the campaign trail, more willing to show a personal side and more open about his age.

“I’ve been criticised for being old. I plead guilty. I am old. But there are advantages to being old,” he said in late October, arguing that he has a decades-long track record that his opponents don’t have.

Sanders has said he was surprised to learn that he’d had a heart attack. He has often noted that he was a competitive distance runner in his youth