Sleep is a perennial problem in our gadget-obsessed industrial civilization, so much so that an entire industry has been built around trying to help us get more of it. From apps that track sleep to pharmaceutical drugs to sleep aids like white noise machines, the global sleeping aids market is expected to reach $118 billion by 2030.

Though sleep seems like a ubiquitous problem, it hasn't always been this way.

"Sleep is kind of a new topic in medicine, even 20 years ago, we didn't know the role that sleep played in getting rid of amyloid plaques, which would lead to Alzheimer's disease or cognitive impairment," Dr. Pedram Navab, a neurologist, sleep medicine specialist and author of "Sleep Reimagined: The Fast Track to a Revitalized Life," told Salon. "Now we know so much more about sleep and people have these trackers and these electronic devices."

Navab said he will have patients come in and make claims like they "didn't get enough REM sleep." He sees people who suffer from sleep disorders.

"And I'm like, 'You know what? You need to get rid of that stuff," Navab said. "You just need to go to sleep, you don't need to figure out how much you have, if you're able to go to sleep naturally you will get what you need, you don't need to track it down."

Humans weren't always problematizing our sleep. In fact, sleep looked very different before the industrial revolution, which is when electrification began — and, in turn, electric lighting. Currently, the Centers for Disease Control and Prevention (CDC), suggests adults over the age of 18 need 7 or more hours per night. Yet before the invention of light, people frequently slept in two segments.

"During the industrial revolution, when the sun went down, there was no electricity so people had to sleep," Navab said. "And then they kind of woke up for the second time, [known as] the second sleep and they journaled or whatnot."

This is referred to as biphasic sleep. Prior to biphasic sleep, some historians believe that hunter-gatherer societies slept in one smaller stretch throughout the night — closer to how we do now. Indeed, when researchers studied the sleep patterns of three preindustrial societies in Africa and Bolivia they found that these ancient humans got only 6.4 hours of sleep within a 24 hour day in grass-made beds.

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Historian Roger Ekirch looked back at prayer manuals from the late 15th century, which offered specific prayers for the time in between sleeps. A doctor's manual from the 16th century advised couples to conceive "after the first sleep." "Families rose to urinate, smoke tobacco, and even visit close neighbors," Ekirch wrote in his book, "At Day's Close: Night in Times Past." "Many others made love, prayed, and most important historically, reflected on their dreams, a significant source of solace and self-awareness."

"What I have argued and feel confident doing so given the considerable evidence that I have uncovered over the last 20 plus years is that biphasic sleep was the predominant form of human slumber in the Western world, prior to the mid 19th century," Ekirch told Salon in an interview. "It began to fade gradually over the course of the 19th century while the industrial revolution was still, of course, fully underway."

Navab said typically the first sleep began two hours after dusk. People woke up for an hour or two — after four to six hours of sleep — and then went back to sleep until dawn.

But by the 1920s, the idea of two sleep sessions, and enjoying what happened in between, began to fade.

"It was not an overnight transition," Ekirch said. "It took place over the course of the 19th century, and there were still remote rural areas in the early 20th century in which the inhabitants exhibited biphasic sleep."

Ekirch said the transition happened as a result of technological and cultural changes of the industrial revolution. Cities were lit up at night — first by gas lanterns, and then with electric bulbs. Electrification also meant that factories could operate 24 hours a day, which led to the prominence of night shifts in the industrial workplace. Within decades, the human relationship with sleep changed due to all of this.

"People, especially in urban areas and primarily middle class, began adopting many of the values associated with industrialization, ambition, profit-seeking, efficiency, punctuality," Ekirch said "And a widespread reform movement arose in the United States and in Great Britain, known as the Early Rising Movement, beginning roughly in the 1830s."

From a medical standpoint, Navab said there isn't an issue with segmented sleep.

"I don't think that's an issue as long as you're able to go back to sleep and get sufficient hours of sleep," Navab said. "As long as they're waking up when the sun is coming back up, I think that's really the most important thing, and they're going to bed when it's night, those are really the most important things."

In fact, Ekirch has argued that this is the more natural way to sleep.

"My argument has been, and this has been backed up by some prominent sleep scientists, that one reason why some people do suffer from what has been termed middle of the night insomnia is that many of these cases, these individuals are experiencing a powerful remnant or echo of this long, dominant pattern of biphasic sleep," Ekirch said. "I've been told over and over again that it eases the anxiety of individuals who suffer from insomnia."

Another way that sleep has changed over the last 150 years is that more people sleep alone.

"Families used to have to sleep together, there was one big bed with like four or five people in the bed and so they all had to kind of learn to sleep together and try to suppress whatever issues they had during that period," Navab said. "But I think that has actually created more insomnia."

While it might sound counterintuitive, Navab said, people sleeping in more solitary environments gives them more room to ruminate.

"If you've got any issues going on, that's going to affect your inability to sleep," Navab said. "And then also, you're kind of alone in the bed so you can do whatever you want without disturbing anyone." In this case, it can be easier to stay up all night looking at one's phone when there isn't someone else in bed to tell them to stop it because they're disturbing their sleep.

Overall, the focus on sleep in our modern society — Navab believes — is causing more anxiety.

"Everything was much more natural [back then]," Navab said. "The performance anxiety wasn't there as it is now with all these new electronic gadgets."