A new study published on February 25 suggests a link between insomnia and a heightened risk of cardiovascular diseases and conditions, such as myocardial infarction, otherwise known as a heart attack.

Insomnia is a common sleep disorder that affects a person’s ability to fall asleep, and stay asleep. It can result in drowsiness upon waking and have a negative effect on energy levels and mood. People can experience short-term insomnia, which may last for days or weeks, or chronic insomnia that lasts for months or more.

The new study notes that this affliction is the most common sleep disorder in the United States, observing that 10% to 15% of people suffer from the condition.

The ideal amount of sleep for the average adult is between seven and nine hours per night, according to the CDC.

“A lot of studies have pointed somewhere between seven and eight hours of sleep being the magic number for us,” said Dr. Martha Gulati, director of prevention at the Cedars-Sinai Smidt Heart Institute, according to CNN. Gulati is not connected with the study. “There is obviously variability for everyone, but too much sleep is rarely the issue.”

Scientists conducted previous research on the relationship between insomnia and cardiovascular conditions in 2017. This study noted a “high prevalence” of insomnia among patients with cardiovascular afflictions and heart failure.

Current heart attack prevention guidelines address factors such as obesity and weight gain, which are known to increase a person’s risk for cardiovascular disease. Despite this longstanding link, not only are obesity rates continuing to rise across the country (especially in Texas) but children are also being increasingly affected.

The authors of this new study noted that, as of the time of their research, insomnia is a glaring omission from these heart attack prevention guidelines.

Their findings were based on the observation of over 1,000,000 adults from nations including the United States, Norway, the UK, Germany, Taiwan, and China. Of these, 153,881 were afflicted with insomnia while 1,030,375 were not.

While heart attacks were only observed in 1.6% of insomniac subjects and 1.2% of others, the study showed the insomniac group was 1.69 times more susceptible to heart attacks than people without insomnia.

The researchers concluded that, because of this correlation, insomnia should be included in heart attack prevention guidelines.

Gulati told CNN that the likely reason why insomnia would elevate a person’s risk of cardiovascular disease is that it creates a cortisol imbalance. Cortisol is known as the stress hormone.

“What really happens when you’re not getting enough sleep is that your cortisol gets out of whack,” Gulati said. “If you are having sleep problems, we know that your blood pressure is more elevated at night.”