More than four months after suffering a heart attack on the campaign trail, Sen. Bernie Sanders refuses to release detailed medical records that might yield clues about his overall health.

Sanders, 78, said multiple times last year that he would share his medical records. On Dec. 30, he released three paragraphs from two cardiologists and a two-page letter from a primary care doctor proclaiming him to be in good health.

But during a CNN town hall last week, Sanders said he divulged “quite as much as any other candidate has” on their medical records. When again asked whether he would release full medical records, he said, “I don’t think we will, no.”

His refusal to release detailed records became a topic during Wednesday’s debate in Las Vegas and continued through the week as Sen. Elizabeth Warren said “he just hasn’t” released his records as promised.

The lack of transparency raises questions about the Democratic front-runner's health that medical experts say could be answered – and silenced – with the release of detailed records.

Neither Sanders nor three other Democrat candidates ages 70 or above have provided the same level of medical detail that Sen. John McCain did just over a decade ago. President Donald Trump, 73, also eschewed precedent, releasing to the public only a laudatory physician letter rather than medical records.

In December, former Vice President Joe Biden, shared a letter from his doctor describing him as a "healthy, vigorous 77-year-old." Warren, 70, also provided a one-page letter from her doctor along with five pages of lab results.

While he was the presumed Republican nominee on the presidential campaign trail inMay 2008, McCain, then 72, released detailed medical records on his heart health, skin cancer and other conditions, including assessments by his own physicians. McCain also allowed media outlets to briefly review the records with outside medical experts.

Dr. Stuart Flynn, then dean of the University of Arizona College of Medicine in Phoenix, reviewed 1,173 pages of McCain’s medical records at the request of The Arizona Republic.

The detailed records provided by McCain provided a comprehensive view of his health, Flynn said. His independent review concluded the Arizona senator had a clean bill of health, despite injuries sustained as a prisoner of war in Vietnam and multiple battles with melanoma.

Sanders refusal to provide more details will likely fuel more questions about his health.

“It’s the classic glass half empty,” said Flynn, now dean of Texas Christian University and University of North Texas School of Medicine in Fort Worth. “If he’s not telling us something, then there must be something there. I don’t think that has to be the case at all, but I can’t say it isn’t until he comes forward with the records.”

Cardiologists not involved in Sanders' care say the first four to six weeks after a heart attack is a crucial period for recovery. He had a heart attack Oct. 1 during a campaign event in Las Vegas. He had a blockage in one artery and two stents were inserted. He was released from a hospital there three days later, according to a letter released by the Sanders campaign.

“In a heart attack, the most important thing is the amount of damage a heart has sustained,” said Guy L. Mintz, director of cardiovascular health and lipidology at Northwell Health’s Sandra Atlas Bass Heart Hospital in Manhasset, New York.

Heart tissue that is damaged cannot be repaired. A key measurement, ejection fraction, gauges how much blood the heart pumps. A low measure suggests a major heart attack with significant tissue damage.

"There are people who have mild, moderate or big heart attacks," he said. "I don't necessarily think he had severe heart attack because he would have been hospitalized longer. And he would not be back on the campaign trail and in the Senate so quickly."

Doctors have continued to monitor Sanders progress. In December, during a treadmill exam, Sanders' "performance was rated above average" compared with that of similar-aged patients, according to a December letter from Brian P. Monahan, the attending physician of Congress.

Sanders cited his frequent campaign stops as proof of his vigor and stamina. During the debate, Sanders pointed out that former New York Mayor Michael Bloomberg also has two stents.

In December, Bloomberg's campaign disclosed in a letter that he had a coronary stent placed for a blocked artery in 2000. In 2018, he was diagnosed with atrial fibrillation, which is an irregular heartbeat. The letter described him as being in excellent health.

"The question for both of them is how strong is their heart," Mintz said. Without a detailed release of medical records, "I don't think you'll find that information."

Flynn said detailed medical records could reveal other signs of vascular disease that would give the public a more robust picture of Sanders' overall health. Such detailed records also could reveal potential risks for future heart attack or stroke.

Or the records could silence chatter about his health on the campaign trail.

"It wouldn’t be bad for a 78-year-old, if he had that information, to come out and slam it on the table," Flynn said.