Travis Bradberry, writing on LinkedIn, has a nice summary of current thinking about sleep deprivation and productivity:

the short-term productivity gains from skipping sleep to work are quickly washed away by the detrimental effects of sleep deprivation on your mood, ability to focus, and access to higher-level brain functions for days to come. The negative effects of sleep deprivation are so great that people who are drunk outperform those lacking sleep.

Or, if you’re too drowsy to read the article, just look at this: