Even when accounting for other factors, the right amount of sleep has been shown to have a big impact on heart attack risk.

Goldilocks famously sought the "just right" choice of three options – and as it turns out, her discernment may serve us well when thinking about sleep. A new study published in the Journal of the American College of Cardiology has concluded that getting too little sleep – or too much – can boost your risk of heart attack. Even for non-smokers who exercise and have no genetic predisposition for cardiovascular disease, getting the "just right" amount of sleep can offset the risk.

For the study, the scientists looked at the genetic information, self-reported sleep habits, and medical records of 461,000 UK Biobank participants ranging in age from 40 to 69 who had never had a heart attack. After following them for seven years, they found this, writes the University of Colorado Boulder:

Compared to those who slept 6 to 9 hours per night, those who slept fewer than six hours were 20 percent more likely to have a heart attack during the study period. Those who slept more than nine hours were 34 percent more likely.

"This provides some of the strongest proof yet that sleep duration is a key factor when it comes to heart health, and this holds true for everyone," said senior author Celine Vetter, an assistant professor of Integrative Physiology at University of Colorado at Boulder.

And this sweet spot of six to nine hours isn't just for people without genetic risk. When they looked exclusively at people with a genetic predisposition to heart disease, they discovered that sleeping between six and nine hours per night reduced their risk of having a heart attack by 18 percent.

"It's kind of a hopeful message, that regardless of what your inherited risk for heart attack is, sleeping a healthy amount may cut that risk just like eating a healthy diet, not smoking, and other lifestyle approaches can," said lead author Iyas Daghlas, a medical student at Harvard.

Other research has come to similar conclusions, but mostly by means of observational studies which do not prove cause and effect. For this study, using a large cohort dataset and looking at combined observational and genetic research allowed the team to approach the topic in a different way.

The researchers took into account 30 other factors aside from sleep – things like body composition, physical activity, socioeconomic status and mental health – yet still concluded that sleep duration, "in and of itself, influenced heart attack risk independently of these other factors."

And the more people veered from the six-to-nine hour range, the more pronounced the risk became. The University explains:

For instance, people who slept five hours per night had a 52 percent higher risk of heart attack than those who slept 7 to 8, while those who slept 10 hours nightly were twice as likely to have one.



The researchers did not explore the "why" here, but other research has arrived at some possibilities. A short sleep can have an impact on the lining of the arteries, and impact bone marrow development of inflammatory cells. Meanwhile, too much sleep may boost inflammation, which is also associated with heart disease.

"Just as working out and eating healthy can reduce your risk of heart disease, sleep can too," said Vetter. That is, as long as it's not too little and not too much, but just right.