According to the Centers for Disease Control and Prevention, one out of every three Americans gets less than the recommended seven hours of sleep per night. Whether that lack of sleep is caused by too much stress, too much caffeine, a poor diet or looking at our phones too late into the night, many solutions, both pharmaceutical and ergonomic, have been offered to cure what ails us.

The most simple way to improve our sleep would seem to be the position we lie in. I was always told that the healthiest way to sleep was flat on our back, or with a pillow nestled between our legs if we prefer to lie on our side. But Dr. Matthew Edlund of the Center for Circadian Medicine says it’s more complicated than that.

“People think they sleep in one position, but they move all the time,” Edlund says. According to him, we can be in 790 different positions in a single night. “People have a natural reaction to go from one space to another. I have video logs of what people are doing in their sleep. People who were convinced they sleep in one position are shocked how much movement they have at night.”

But is there a best position to be in for a good night’s rest? Dr. Edlund says it’s entirely dependent on the person.

Many studies claim that sleeping on your back is the best position for your health. It can help alleviate back pain, reduce tension headaches and prevent wrinkles from forming on your face. But, Edlund explains, if you have sleep apnea, sleeping on your back can make your condition worse.

Some people will spend hundreds of dollars on pillows to help them with their sleep, and if you suffer from certain conditions, it might be worth the money. “If you have acid reflux, or allergies, sleeping in an elevated position can help,” Edlund says. “It might be worth spending money on a V-shaped pillow.”

Most people sleep on their side, and it is apparently best to sleep on your left side, because that reduces pressure on your heart when compared to sleeping on your right side. But, again, the problem is that people move so much in their sleep that your position can be hard to control.

But sleeping on your stomach is the worst, right? Lots of doctors will recommend against sleeping on your stomach because it’s bad for your neck and back. If you sleep on your stomach every night, because your neck and spine are in a twisted position, you are liable to herniate or rupture a disc.

So sleeping on your stomach should be avoided at all costs, right? Again, Edlund says it really depends on the person. “Given the dynamics of the kind of viral pneumonia that Covid produced, sleeping on your stomach became life saving,” he says. So while sleeping on your stomach might wreck your neck, depending your health circumstances, it could save your life.

So what is the best way to sleep, then? Edlund says it’s to sleep alone. A recent New York Times article surveyed 2,200 couples and found that one in five couples sleep in separate bedrooms, with two thirds of them doing it every night. The story reported that interior designers are seeing increased requests to create secondary sleeping rooms. “With overall sleep quality, it’s clear that one person will sleep better than two," Edlund says.