Obesity. Diabetes. Heart disease. Mood disorders. Even the common cold.

When you don’t get enough sleep on an ongoing basis, you’re at higher risk for developing all of these health problems.

That’s what we’ve been told repeatedly in recent years by sleep organizations, government health agencies and high-end mattress companies.

Countless studies indicate that adults need seven to eight hours of sleep a night. Getting only four or five hours occasionally won’t kill you, but making a habit of it just might.

Conventional wisdom also says that people used to sleep a lot more back when there wasn’t much else to do at night. Technological advances, we’re told, have disrupted our “natural” sleep patterns, keeping us awake longer and turning us into a society of fat, wheezing, depressed zombies.

A new study, however, calls into question the notion that we’re sleeping less than people did back in simpler times. It also casts doubt on insufficient sleep as the culprit behind the litany of medical nasties it’s being blamed for.

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A team of researchers led by University of California at Los Angeles psychiatry professor Jerome Siegel studied the sleep habits of three “pre-industrial” populations that maintain a hunting-gathering lifestyle similar to that of their ancestors thousands of years ago: the Hazda people of northern Tanzania; the San of Namibia; and the Tsimané, from the Andean foothills of Bolivia.

None of these societies has access to electricity, so their sleep habits are not influenced by the bright lights and entertainment opportunities that keep so many ‘industrialized’ folks up at night.

The scientists found strikingly similar sleep patterns among the three groups. On an ordinary night, they slept about six and a half hours, a bit less than the average American, and less than what organizations like the American Academy of Sleep Medicine say people need. Contrary to popular assumptions about how people slept before electricity, the groups that the researchers observed did not go to sleep as soon as the sun set. They stayed up for a few hours after dark, with only a small fire for warmth and to keep unwanted animals away. They also awoke about an hour before sunrise most days.

While these groups don’t sleep any longer than average Americans, they do seem to sleep better. They rarely wake up during the night. Insomnia is extremely rare, afflicting only about 2 percent of the population, compared to as much as 30 percent in some advanced industrial countries.

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Researchers also found that people in the three societies they observed typically get all of their sleep in a single chunk. They don’t have much use for daytime naps, and there was no evidence of the “segmented” sleep pattern that some historians think was prevalent prior to the introduction of electric lights, in which people got their nighttime sleep in two separate intervals — “first” and “second” sleep — separated by an hour or more of wakefulness and activity.

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The Centers for Disease Control and Prevention considers insufficient sleep a serious public health problem in the United States, with a third of American adults typically getting less than the seven to eight hours of sleep they say is needed for optimal health. The problem, according to the CDC website, “may be caused by broad scale societal factors such as round-the-clock access to technology and work schedules.”

Yet the groups that scientists tracked in the study slept less than the recommended amount without the influence of either jobs or gadgets, and they appeared to be relatively fit and healthy, with no prevalent chronic diseases.

So what does this mean for bleary-eyed Americans worried that their habitual late-night “Walking Dead” binge-watching is ruining their health? If you generally get nearly enough sleep and mostly feel OK, probably nothing.

Related: Surprising Sleep Secrets

But if you go to bed at a reasonable hour most nights and still have trouble getting enough sleep, you could have a sleep disorder, so a visit to the doctor may be wise. The CDC says that major sleep disorders include:

  • Narcolepsy — excessive daytime sleepiness combined with sudden muscle weakness; episodes of narcolepsy are sometimes called “sleep attacks” and may occur in unusual circumstances.
  • Restless legs syndrome (RLS) — an unpleasant “creeping” sensation associated with aches and pains throughout the legs that can make it difficult to fall asleep.
  • Sleep apnea — interrupted sleep caused by periodic gasping or “snorting” noises or momentarily suspension of breathing.

The National Institutes of Health suggest you keep a sleep diary to track of how much quality sleep you’re getting and to help determine whether you have a sleep disorder.

It takes more than a single study to debunk the wealth of existing evidence about the importance of sleep. But as with the ever-shifting federal guidelines about how we should eat, it’s worth paying attention to ongoing research to keep up on the best, latest advice about how we should sleep.