The stress of the modern workplace is causing many workers to lose sleep, and that's not just a figure of speech. In a survey conducted by the Harvard Business Review, nearly half of the 180 business leaders surveyed responded that they do not get enough sleep at least four nights a week. While many may see this as coming with the territory of a high-stakes career, it’s actually extremely problematic, both personally and professionally. Studies have shown that there is a strong correlation between leadership performance and getting enough sleep at night. The last part of the brain to evolve was the neocortex, which is responsible for sensory perception, motor commands, and language. The frontal neocortex is responsible for high-order cognition—planning, problem solving, and reasoning—the functions that leaders need to hone to be effective. Studies have shown that while many areas of the brain can function just fine with little sleep, the frontal neocortex cannot. Simply put, when leaders don’t get enough sleep, they cannot lead effectively. This is why it’s important for leaders to unplug and relax, and ensure that they get the recommended eight hours of sleep a night.