Not getting a full nights rest is bad for everyone. You'll wake up cranky, body aching, and everyone will notice your downer attitude throughout the day. But many people brag how they only need about 4 hours of sleep to be fully functioning. There are even some people that claim to work days on end without any sleep. The truth is that this is terrible for your body, since it needs good sleep in order to repair itself.
With just 4 to 6 hours of sleep, you're just surviving and leaving your body vulnerable to becoming sick. You have to give your body enough time to heal itself after a long day of activity.
External Sources:
Memory Foam Mattress Pads: Cure for Insomniacs
Help! I Can't Sleep - How To Use A Memory Foam Mattress Pad
