In his long-awaited memoir, Greenlights, which is set to come out today, Matthew McConaughey has revealed that his father, James Donald McConaughey, died of a heart attack while having sex.

The 50-year-old actor told PEOPLE that his father died in 1992 and that his “knees buckled” when his mother told him what had happened.

McConaughey said, “I couldn’t believe it. He was my dad. Nobody or nothing could kill him, except mom.”

However, it turned out that James predicted the cause of his death. McConaughey said, “He’d always told me and my brothers, ‘Boys, when I go, I’m gonna be makin’ love to your mother.’ And that’s what happened. He had a heart attack when he climaxed.”

Experts say that sex usually increases a person’s heart rate.

Florida-based cardiologist Dr. Leonard Pianko told Health, “Any physical activity will elevate your heart rate, whether you are swimming, running, or having sex, and your risk for a heart attack increases whenever your heart rate is elevated.”

According to Dr. Victoria Shin, a cardiologist with Torrance Memorial Medical Center in Torrance, California, sex increases adrenaline levels, heart rate, and blood pressure.

“This is what we do when we subject patients to ‘stress tests’ in the office or hospital to unmask any underlying heart problems,” Dr. Shin told Health. “Sexual activity is a form of ‘stress testing,’ and if someone has underlying heart disease that is undiagnosed, it can manifest as symptoms of chest pain or in the worst-case scenario, cause a heart attack or sudden cardiac death.”

Although it is rare to have a heart attack during sex, it may happen in some people, of course, McCounaghey’s dad is one such rare case.

A 2017 study, published in the Journal of the American College of Cardiology, has suggested that it is extremely rare to die from a heart attack while having sex, even if you have existing heart disease.

Dr. Pianko said, “If you have a blockage to your heart and you overexert yourself both physically and emotionally, it may in rare instances precipitate a heart attack.”

However, a person’s overall health status can influence the risk.

Dr. Shin explained, “For a healthy 50-year-old man, the risk of having a heart attack in any given hour is about one in a million. Sexual activity doubles the risk, but it’s still just two in a million.”

For a man with heart disease, the risk of having a heart attack is 10 times higher. “But even for them, the chance of suffering a heart attack during sex is just 20 in a million,” Dr. Shin added.

Dr. Shin continued, “If you or your partner takes erectile dysfunction medications, such as Viagra, you should also check with your doctor to make sure you’re not on any conflicting medications that could cause heart issues,”

Nevertheless, keeping your heart health optimal is the key. Dr. Robert Zaloom, a cardiologist at NYU Langone Hospital–Brooklyn, told Health, “Sexual activity requires a healthy heart and generally taking good care of yourself. This means good diet and nutrition and regular exercise, particularly when you’re over 50.”