Mysteries of Sleep

After much research it became apparent that the healthiest you can count people who usually sleep 6, 5-7, 5 hours. They have the lowest rate of cardiovascular disease and mortality.
In those who sleeps at least 4, 5:00, shortened life expectancy, on average, 1, 6 times. It has been observed, even more dangerous sleep regularly over 9, 5:00 - this reduces the life of 1, 7-1, 9 times.
The pattern is revealed, but to explain why it happens so, scientists have not yet taken. If too short a dream more or less clear - from insufficient rest the body wears out faster, the causes of high mortality among heavy dormice remain a mystery. Perhaps we are talking about the feedback - too much sleep those whose health is not okay. However, doctors are reminded that universal recommendation on the duration of sleep, they can not give. It is only the time necessary and sufficient for most people. For each person has its own optimal duration of sleep, depending on lifestyle, occupation, health, and even the climate of the country in which he lives.

Somehow now goes to bed afraid. Well how wrong number of minutes will give Morpheus, what then?