President Donald Trump prides himself on getting by with just four or five hours of sleep at night, which leaves him plenty of time early in the morning to scan cable TV news and tweet before going to work. During last year’s rough-and-tumble campaign, he scoffed at “low-energy” rivals Republican Jeb Bush and Democrat Hillary Clinton for carving out nap time.

“No naps for Trump! I don’t nap,” the 71-year-old Trump bellowed during one campaign stop. “We don’t have time.”

Yet history is replete with powerful leaders and warriors such as Napoleon, Winston Churchill and John F. Kennedy who routinely napped in the afternoon, regardless of the crises swirling around them. “Nature has not intended mankind to work from eight in the morning until midnight without the refreshment of blessed oblivion, which even if it only lasts twenty minutes, is sufficient to renew all the vital forces,” Churchill once wrote.

And increasingly, science is siding with the nappers, with researchers finding that short sleeps not only are beneficial to drowsy individuals and the elderly but also are essential to public health, public safety and economic productivity.

“Now, I don’t know Donald Trump nor have I done sleep studies on him,” said Philip M. Alapat, an assistant professor specializing in pulmonary disease and sleep disorders at the Baylor College of Medicine in Houston. “But the number of people that can truly function optimally with four or five hours of sleep on a nightly basis are vanishingly few.”

An international team of neurologists recently published a study showing how sleep deprivation can disrupt brain cells’ ability to interact and communicate. A night of lost sleep can result in temporary mental lapses that impair memory and distort visual perceptions, according to the study published in early November in the journal Nature Medicine.

Itzhak Fried, the senior author and a professor of neurosurgery at the David Geffen School of Medicine at UCLA and Tel Aviv University, said in a statement that his team discovered that “starving the body of sleep also robs neurons of the ability to function properly.”

Another recent study, published by the Journal of the American Geriatrics Society, focused on 3,000 older people in China and examined whether those more inclined to take brief naps performed better on mental ability tests.

Scientists found that people who took a nap after lunch did better on the mental agility tests than those who did not sleep in the middle of the day. The study concluded that one hour was the optimal nap length and that people who had much longer or shorter rests — or no naps at all — performed up to six times worse on memory and math tests.

The latest research dovetails with longtime warnings about the dangers of insufficient sleep.

Over the years, sleeplessness has quietly grown into a pervasive problem. One-third of American adults regularly get too little sleep, according to the Centers for Disease Control and Prevention. Nearly half of all American adults complain that poor or insufficient sleep affects their daily activities at least once a week, according to the National Sleep Foundation. What’s more, an estimated 50 million to 70 million Americans have chronic sleep disorders, according to a health survey for the CDC.

Scientists have linked sleep deficiency to many chronic health problems, including heart and kidney disease, high blood pressure, diabetes, stroke, obesity and depression.

While the relationship between sleep deprivation and adverse health consequences is not fully understood, according to Alapat, a lot of it has to do with denying the body the rest it needs for healing and to refresh the neurons in the brain, as well as to fight off poisonous substances. “There are toxins that essentially accumulate in the brain that need to be cleared out with sleep” to avoid long-term threats to the immune system and cardiovascular functions, Alapat says.

In general, Alapat recommends that naps last no longer than 30 minutes. When a person falls asleep, the brain goes through several stages of sleep, ultimately leading to the deepest stage, known as rapid eye movement sleep, or REM. Once a person reaches that dreamy state, it becomes much more difficult to wake up clearheaded, refreshed and fully functioning.

Of course, it’s easy for Alapat and other scientists to recommend a short nap in the afternoon for the sleep-deprived. For most American workers, finding a time and place to squeeze in a nap in the middle of the day is highly challenging at best. That’s especially true in a highly competitive work environment where nappers are frequently stigmatized as lazy or laggards.

However, those attitudes are beginning to change as some employers begin to see the value of having a well-rested and refreshed workforce. A September 2011 study in the Journal of Sleep concluded that employee insomnia was costing U.S. companies a startling $63 billion a year in lost productivity.

Some of the nation’s most innovative companies — including Google, Ben & Jerry’s, Uber, PwC and HuffPost — have installed napping spaces for their workers.

Alapat cautions that while naps may provide a short-term boost in alertness and performance, they can’t regularly make up for lost sleep.

“What we have found is that people who are perpetually sleep-deprived … tend to have adverse health consequences,” he said. “And so if you are having to use naps on a daily basis to make up for what appears to be chronic sleep deprivation, you are probably looking at a situation where you’re adversely affecting your health overall.”