For starters: They don't need alarm clocks,stick to their bedtimes, and don't sleep with their smartphones.
You may feel super productive by pulling all nighters, and but you're actually less productive when you're running on very little sleep. inadequate sleep can not only inhibit (restrain; prohibit; retard or prevent) concentration,but can also cause anxiety, irritability, or affect your ability to retain information,which all results in poorer productivity.
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Source: fastcompany.com