Total lack of sleep will kill you quicker than lack of food. (If you go 10 days without sleep you're toast, whilst starvation takes a few weeks. In fact if you go for more than three days without any sleep at all, you will lose orientation in place and time, you will hallucinate and eventually your body will begin to break down. The average human requires between seven and eight hours of sleep every night. This enables the body to repair and refresh itself in order to start the new day. If you try to burn the candle at both ends and don't get enough sleep, it will affect everything that you do. Mistakes can be made, accidents can happen and there is evidence of short-term memory. Good news for the over 60s is that you can get away with between five and six hours sleep.)