Sleep is time to repair the cells and to organize and fix what you memorized. If your sleep is insufficient, you can’t repair what you have to repair and the next day comes in that condition.
Insufficient sleep causes contraction of blood vessels, fast heart beet and high blood pressure. High blood pressure raise a risk of stroke, cardiac infarction, depression and diabetes. They say that high blood pressure triples the risk of diabetes.
It is natural that hours of sleep becomes shorter with age. The time you feel sleepy becomes earlier, resulting in waking up earlier and deep sleep tends not happen.
Required hours of sleep depend on the age. 20s needs about 7hours 45 minutes, 30s to 40s needs 7 hours, 50s to 60s needs 6 hours and more than 70 needs 5 hours 45 minutes.