It’s no secret that sleep is important to your overall health, but a lack of sleep could have substantial effects on your heart, a new study shows. The researchers said people with insomnia are more likely to have a heart attack.
Insomnia is the most common sleep disorder in the US, the researchers wrote in their report, noting that 10% to 15% of people in the US struggle with it.
The meta-analysis of previously published research, published Friday in the journal Clinical Cardiology, suggests that the potential association between insomnia and heart attack risk is strongest in women.
Dr. Martha Gulati, director of prevention at the Cedars-Sinai Smidt Heart Institute, said that most of her patients are women and that insomnia is a noted risk factor for women who have had any form of ischemic heart disease.
“Insomnia is actually quite common. We see it probably in 1 in 10 patients in the United States,” said Gulati, who was not involved in the new research. “It is my impression that almost everyone experiences insomnia at some point in their life. The estimate is that 1 in 2 adults experience it at some point in their life, maybe in the short term because of stressful moments.”
For their analysis, the researchers – from medical institutions in Egypt, Saudi Arabia and Pakistan, as well as SUNY Medical University and Harvard Medical School in the United States – defined insomnia as a sleep disorder with three main symptoms:
- Difficulty falling asleep
- Difficulty staying asleep
- Waking early and being unable to fall back asleep
The analysis included more than 11 years’ worth of data from 1,184,256 adults in the US, the UK, Norway, Germany, Taiwan and China.
Of the participants, 153,881 had insomnia and 1,030,375 did not. The researchers found that those with insomnia were 1.69 times more likely to have a heart attack than people without insomnia. Heart attack numbers were still relatively low – occurring in about 1.6% of people with insomnia and 1.2% of those without.
The study also found an association between increased heart attack risk and how long a participant slept each night. Those who slept five hours or less had the highest association with heart attack risk and were 1.56 times more likely to have a heart attack than people who slept seven or eight hours.
Longer sleep duration wasn’t always more protective. The study found that people who slept six hours a night had a lower risk of a heart attack than those who slept nine hours or more.
“A lot of studies have pointed somewhere between seven and eight hours of sleep being the magic number for us,” Gulati said. “There is obviously variability for everyone, but too much sleep is rarely the issue.”
The study says that the increased heart attack risk among people with insomnia persisted regardless of age or gender.
Gulati said there are several ways a lack of sleep can create a higher risk of a heart attack. The regulation of cortisol is central.
Cortisol is a hormone responsible for regulating the body’s response to stress. If levels are too high, it will raise the body’s blood pressure. When a person sleeps well, their blood pressure goes down at night.
“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.”
Higher blood pressure at night caused by cortisol imbalance is one of the potential pathways to an increased risk of heart disease, she said.
The authors of the study said insomnia should be considered a risk factor in guidelines for the primary prevention of cardiovascular disease.
“Now we have evidence that sleep is medicine,” said the study’s senior author, Dr. Hani Aiash, a cardiologist and assistant dean of interprofessional research in the College of Health Professions at Upstate Medical University. “So good sleep is prevention.
“If you didn’t sleep well … below five hours or six hours, you’re exposing yourself to a higher risk of myocardial infarction. The pattern of sleep is very important.”
However, “we don’t need nine hours,” Aiash said. “Above nine hours is harmful also.”
To avoid insomnia and improve sleep, the US Centers for Disease Control and Prevention recommends five simple steps:
- Being consistent with going to sleep at the same time each night and getting up at a similar time every morning, including weekends. This helps establish a rhythm for your body.
- Make sure your bedroom is a relaxing, quiet and dark space with a comfortable temperature.
- Next, remove smartphones, TVs and computers from the room.
- Avoiding large meals, caffeine and alcohol before bedtime gives your body the best chance at sleeping well.
- Finally, remain active during the day.
If you’re still struggling with insomnia, talk to a doctor about other remedies and treatments, the CDC says.
Correction: This story has been updated to reflect that Dr. Hani Aiash is the senior author of the new study.
CNN’s John Bonifield contributed to this report.