Sleep deprivation is no joke.
Even moderate fatigue can hit you as hard as alcohol intoxication, according to a helpful chart from the Harvard Business Review.
However, many top executives and leaders seem to swear by skimping on shut eye.
Some of them might be part of the “sleepless elite.” Others are probably just good at masking the effects of exhaustion.
Unless you’re one of those lucky people who doesn’t get tired, your best bet is to avoid emulating these individuals when it comes to your sleep routine:
1. Twitter cofounder and CEO and Square CEO and founder Jack Dorsey sleeps four to six hours a night
Being at the head of two exciting tech startups doesn’t leave too much time for rest. In 2011, Dorsey told Kara Swisher that he was spending eight to 10 hours a day at Square, and eight to 10 hours a day at Twitter.
That left him somewhere around four to six hours a night to sleep, possibly less when travel time is factored in. He still manages to get up at 5:30 every morning to take a jog.
2. President Donald Trump gets three to four hours of sleep a night
“How does somebody that’s sleeping 12 and 14 hours a day compete with someone that’s sleeping three or four?” he asked the Daily News.
3. PepsiCo Chairperson and CEO Indra Nooyi gets four hours of shut eye each night
She’s no stranger to long hours, having worked the graveyard shift as a receptionist while getting her Master’s at Yale.
4. Helena Morrissey, head of personal investing at Legal & General Investment Management, sleeps for five to six hours
Morrissey told The Guardian that she gets up “at 5 in the morning, sometimes earlier,” and immediately starts sending emails until her kids get up. She has family dinner scheduled at 7:30 p.m. but works again after that, sometimes for as much as two hours, prepping for the next morning’s meetings.
She gets five to six hours of sleep each night and admits to feeling a bit sleep deprived. But that’s the job, especially when you’ve got nine children in addition to running a global investment company.
5. Fashion designer and director Tom Ford sleeps three hours a night
After dropping out of NYU to pursue a career in fashion design, Ford quickly landed a position as design director at Gucci. Under his leadership, Gucci’s value increased by 90%.
He does not attribute this success to talent, but says it’s due to his energy. It must be pretty intense, considering that Ford sleeps only three hours a night.
6. AOL CEO Tim Armstrong sleeps six hours
Armstrong wakes up around 5 a.m., is out of the house and working from his car by 7 a.m., and works until 7 p.m. He used to start sending emails immediately after waking up, but now restrains himself until 7 a.m.
He says he tries to get six hours of sleep a night, but often ends up operating on less. “It isn’t ideal,” he told The Guardian.
7. Julie Smolyansky, CEO of Lifeway Foods, gets four hours of sleep
Smolyansky took over the dairy company her father had started in 2002 at the young age of 27.
It took a great deal of work for her to do so. She told Fortune that she managed it by sleeping as little as four hours many nights.
8. Martha Stewart, founder of Martha Stewart Omnimedia, sleeps less than four hours a night
Stewart keeps an impressive schedule while running her business, and according to CNN Money, she sleeps less than four hours a night.
9. Richard Branson, founder of Virgin, usually sleeps five to six hours
The Virgin Group founder is said to only sleep from 12 a.m. to 5 or 6 a.m. every night, according to Forbes — that’s only five to six hours of shut eye.
10. British Prime Minister Theresa May sleeps for five or six hours a night
When she was still home secretary of the UK, May shared that she usually slept five or six hours a night, according to the Telegraph.
She also told the Sunday Times that sleep wasn’t her first priority as prime minister: “In this job you don’t get much time to sleep.”
11. German Chancellor Angela Merkel gets by on four hours of sleep
It’s unclear when Merkel goes to bed, but she has said that she often goes without rest, and can function on only four hours of sleep, according to the BBC.
The Local reported that the German chancellor catches up on sleep on the weekends: “I have camel-like abilities, an ability to save things up — and afterwards I have to fill up again.”
This story originally appeared on Business Insider.