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.According to The Daily News, Trump credits his success to sleeping only three to four hours each night to stay a step ahead of his competition. 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.One of the world's most prominent female executives since getting Pepsi's top job in 2007, Nooyi sleeps a meager four hours a night, according to CNN Money. She's no stranger to long hours, having worked the graveyard shift as a receptionist while getting her Master's at Yale. 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.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. 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.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.Stewart's company produces four magazines, Martha Stewart Living, Everyday Food, Weddings, and Whole Living. She also has a TV show, radio show, and product lines in stores like Staples and Michaels. Stewart keeps an impressive schedule while running her business, and according to CNN Money, she sleeps less than four hours a night.Michael Lewis' profile in Vanity Fair revealed the president's usual schedule while in office: He goes to bed at about 1:00 a.m and is up at 7:00 a.m., meaning he sleeps just six hours a night. Obama sometimes gets less sleep than that. Aides in the White House must constantly decide what type of crisis is important enough to wake the president during his few hours of shut-eye.When asked about his habit of only sleeping five hours a night, Immelt told Bloomberg that he doesn't need much sleep.Iger previously told Fortune he gets up at 4:30 a.m. every morning, to exercise and get work done without distractions. However, that early wake-up sometimes catches up with him later in the day. He also told the New York Times: ''Don't find me at seven or eight at night. I'm a little tough to deal with.'' Carolyn Cutrone and Max Nisen contributed to an earlier version of this post.