Originally Published: 17 AUG 23 17:31 ET

By Jen Christensen, CNN

(CNN) — Someone who has any kind of severe pain a year after a heart attack may be more likely to die within the eight years afterward, according to a new study.

Someone in the US has a heart attack about every 40 seconds, according to the US Centers for Disease Control and Prevention. Heart disease including heart attack is the leading cause of death in the US, but most people survive their first heart attack and go on to lead a normal life, according to the American Heart Association.

The study, published Thursday in the Journal of the American Heart Association, found that people who reported extreme pain a year after their heart attack – even pain that was not associated with heart problems – were more than twice as likely to die in the 8½-year study period.

Pain should be something that both doctors and patients pay close attention to in the months after a heart attack, the researchers said.

Studies show that more people are surviving heart attacks than in previous decades, but there has been little research on the impact of pain on mortality after a heart attack.

For this research, the scientists looked at health data from 18,376 heart attack patients younger than 75 who were tracked by a registry in Sweden between 2004 and 2013. The patients were asked to fill out questionnaires that assessed their pain levels during their follow-up appointments. However, the survey didn’t ask how long the pain lasted.

Pain wasn’t uncommon among the heart attack survivors. At two months after their heart attack, 65% reported some pain. That number had fallen at about a year, when about 45% of the patients reported moderate or extreme pain.

Even at the moderate level, though, people seemed to be at risk of additional serious health problems.

Compared with participants who didn’t report pain, those reporting moderate pain were 35% more likely to die of any cause within the follow-up period. Side by side, pain seemed to be a much bigger indicator of the risk of death than even factors like tobacco use.

The study can’t pinpoint the exact cause of the link between pain and risk of death. Dr. George Dangas, an interventional cardiologist at the Mount Sinai Hospital and chief of cardiology at Mount Sinai Queens in New York City, believes that pain could be a sign of inflammation.

“There could be a mechanism through which the pain sort of aggravates broader systems in the body, including adversely affecting the cardiovascular system,” said Dangas, who was not involved with the study.

People taking medication for extreme pain may also have side effects that could be deadly, he said. Many painkillers, even ones sold over the counter, can increase the risk of cardiovascular problems.

Additionally, pain could be a deterrent to lifestyle changes that might lower someone’s risk of another heart attack, such as exercise.

Dangas said the new study could remind doctors to pay particular attention to their heart attack patients who talk about pain.

“In medicine, we tend to do many studies, many tests, take many images, but at the end of the day, maybe something that is simple, such as the subjective conception of significant pain, might be overlooked a little bit,” he said. “I would say, based on this study, a very basic way to assess pain is very important.”

The researchers found that three demographic groups were more likely to report extreme pain: women, nonsmokers and those with diabetes. Dangas said doctors should be sure they don’t overlook those particular patients when they mention severe pain.

For patients, Dangas said it’s important to be honest with health care providers about how they’re feeling and not to downplay any pain.

Someone who has a heart attack will often go to cardiac rehab, where they’ll get medically supervised instruction on exercises that are good for recovery and for heart health in general. They’ll also get lessons on how to eat healthy and counseling that can help reduce stress levels and manage the depression that can sometimes follow a heart attack. Cardiac rehabilitation cuts the risk of death in the five years after a heart attack by about 35%, according to a 2016 study.

Lifestyle changes like these are often some of the most important things a heart attack survivor can do, especially if they have pain afterward, doctors say.

“For patients with pain, it is of particular importance to reduce other risk factors, such as smoking, high blood pressure and high cholesterol levels,” said study co-author Dr. Linda Vixner, an associate professor of medical science at the School of Health and Welfare at Dalarna University in Falun, Sweden.