My father is 95 yrs. old. In spite of good night's (10 hrs) sleep, he is very drowsy, in patches, during the day. In fact it is difficult to wake him up. refuses to open his eyes and goes back to sleep. In between sleep episodes, he is awake and alert and we think he has got over his tiredness. But he goes back to sleep and we realised it is not tiredness. Cld it be a medical problem? If so what? He does not hv diabetes, and has always had low BP.