It depends. When i'm young and very fit, I can do without
sleep or sleep less than 5 hours a day.
Now as i becoming older and neglecting
exercise, i need sleep, more than 6 hours a
day to maintain alertness.
when u baby u sleep alot lor, then teenager, u sleep less, then
middle age, u sleep lagi less, then old age u sleep only in
daylight, then one day, u sleep forever.
