Unless you are quite unusual, 4-5 hours sleep per day/night is low enough to be bad for your long term health. see http://www.sleepfoundation.org/article/white

Unless you are quite unusual, 4-5 hours sleep per day/night is low enough to be bad for your long term health. see http://www.sleepfoundation.org/article/white-papers/how-much-sleep-do-adults-need http://www.sleepfoundation.org/article/white-papers/how-much... for details.