PR is a stressful job. In fact, it’s the seventh-most stress-inducing job in America.

Sometimes, PR practitioners lie awake at night fretting over any number of issues. That means they’re not getting the eight hours of sleep we hear so much about—yet another thing to stress over.

Thankfully, there’s some good news on this front. A growing body of evidence suggests that the vaunted eight-hour sleep, long touted as a key to productivity, may be unnecessary or even unnatural.

A wealth of accounts reveal that humans once slept in two distinct chunks of about four hours. Generally, these were "a first sleep, which began about two hours after dusk, followed by waking period of one or two hours and then a second sleep," according to a BBC report.

The BBC continued:

Researchers found “references to the first and second sleep [starting] to disappear during the late 17th Century. This started among the urban upper classes in northern Europe and over the course of the next 200 years filtered down to the rest of Western society. By the 1920s the idea of a first and second sleep had receded entirely from our social consciousness."

So don't despair if your clients, bosses or angry journalists are keeping you up. That heralded eight hours in a row of sleep, may be unnatural—as long as your getting that second sleep. And you know what that means. Naps!

The National Sleep Foundation, meanwhile, suggests adults get seven to nine hours of sleep, though it concedes that sleep patterns vary across populations.