Dear Krishnan,,In addition, in case you wake up in between for whatsoever reason,pl utilise the same for a brief sadhana-Bhagavan has stressed the importance of meditation during these transitions. Do not get up abruptly but use it for self enquiry ,gently enquiring who is this being that has waken up,watch your mind .All such interruptions in our sleep may be viewed as not a health problem but an opportunity for sadhana.For as the Gita says,when the world sleeps,the yogi awakes to wisdom. Regds.