Is Donald Trump superhuman? Or is he depressed, cranky, and making poor judgments? Or is he fibbing?

The issue arises because in last week’s Republican debate he mentioned that he sleeps just three to four hours a night. He’s been saying this for years. The day after the debate he claimed to be operating on only 90 minutes of sleep. In evaluating his statements, we’re faced with the three alternatives mentioned above, based on the latest research. And while investigating Donald Trump’s sleep habits may rank low on your to-do list, the issue matters because inadequate sleep is more harmful than most of us realize – and many successful leaders claim, like Trump, to get by on suspiciously little sleep.

PepsiCo CEO Indra Nooyi tells me she sleeps about four hours a night. Fiat Chrysler CEO Sergio Marchionne reportedly sleeps the same amount, as does Martha Stewart; Herb Kelleher reportedly slept four hours while running Southwest Airlines, and Margaret Thatcher did the same as British prime minister. Xerox CEO Ursula Burns tells me she sleeps about five hours, which is how much Bill Clinton reportedly slept as president. And they’re all slackers compared with fashion designer Tom Ford, who reportedly sleeps three hours a night and attributes his success to his energy rather than talent.

Who could blame aspiring leaders for emulating such an impressive group? Yet emulating them could be dangerous, and the danger increases at this time of year, with its focus on meeting annual goals, budgeting, and evaluating employees. For most leaders and up-and-comers, the holidays don’t mean less work; they mean more work and less time in which to do it.

You already know that sleep deprivation is really, really bad for you, but it’s even worse than you think. To summarize, it makes you stupid, depressed, dangerous, unhealthy, and more likely to die. So the question of how much sleep you need is extremely important, and research published just last month is actually somewhat encouraging; it suggests that you don’t need quite as much as you’ve been told. Studying three groups of hunter-gatherers untouched by the modern world, UCLA scientists found they sleep only six to seven hours a night. But that’s still more than all those high achievers cited above.

So are they all lying? My guess is they’re not – not even Trump. Researchers find that a tiny proportion of people, 1% to 3%, can get along fine on four hours or less. Imagine the advantage these so-called short sleepers hold in competitive careers. It makes sense that they’d be heavily over-represented among successful leaders.

Just acknowledge that you’re almost certainly not one of them. (I’m definitely not.) And if you’re not, then trying to be one of them will hurt you, not help you. Take the advice of Arianna Huffington, who has become an evangelist on this topic. Get all the sleep you need. And then, as she says, “sleep your way to the top!”

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