I heard that 4 hours of sleep is better then 6 hours of sleep but 8 hours is the best for you. Is this true?

Well there's always a balance to play out. Too much sleep is as unhealthy as too little, although in most cases, eight is the average suggestion. Also it depends on your age and what kind of life you have. I can get by and function on four hours, but I might be a little moody. Less then that though and it becomes physically hazardous for me, and clients, to pour them coffee. XD It also depends on your sleep rhythm. Do you wake up a lot during the night, or sleep the whole way through? That in itself may affect the length of time you sleep and how acceptable is it, due to all the sleep phases, but we're supposed to sleep the whole way through and it's not supposed to take forever to fall asleep, so those might be signs of a sleep disorder and difficulties that should be looked into. And ha ha look who's talking. XD

I operate better on 4-5 hours a sleep a night. If I get more, then i want more and I end up moody.

No, 4 hours of sleep will shorten your life. In fact even getting 6 hours of sleep per night is a way to shorten your life according to research. It is best to get 8 hours of sleep for proper brain function and to keep our nerves healthy.

"8 hours a night" is an average for the adult population. Some people need less, some more, to be fully rested. It's not generally healthy to sleep longer than you need. It causes a feeling of sluggishness and low energy. On the other hand, getting less sleep than you need is strongly associated in the medical literature with increased rates of obesity, diabetes (type 2), depressed immune function, cancer, heart disease, etc., not to mention its effect on cognition, memory, and general mental well-being. Long-term sleep deprivation (sustained "skimping" on the number of hours each night) is also associated with a variety of mental illnesses, most notably depression and anxiety.

We are not all the same! I am 51 and have gotten 3 to 4 hours of sleep a night for all of my life! I have never failed a physical exam, or been hospitilized for any reason. I wake up fully rested and don't nap durring the day. I am in far better than average mental and physical condition for my age. There are plenty of others like me. The reason for my post is to ask you all a simpe question. "Who among us would not trade time from the old and tired years, to live them while you are young"? That is to assume the studies of sleep and longivity are accurate. Of the studies I read, a 10,14 and 16 year sleep study, there were no conclusive results, only trends and a lot of guess work. On my 51st birthday I had lived the same hours "awake" as a person 63 years 8 months who got the required 8 hours per night. If you are like me and wake refreshed after anything less than 8 hours sleep, don't worry. Worring leads to stress, and stress has been proven to be a major factor in early death.