I listened to today’s issue on CNN.  they discuss sleep loss.  some people said that   it would be average six and half  hour sleep during the week. but researcher said it is properly  about 7 or 8 hour sleep. we often work day and night. we play late night. 24hours store increased. research said a lack of sleep can have serious consequence of health and  cause heart attack , stroke , high pressure. so they recommend to refrain from caffeine coffee and alcohol. they try to make them good sleep. Senior students can have a lack of sleep. they depends on coffee  to fight sleep. I slept for 8hours. I think I  need to shorten sleeping hours.