Hi, Brain white matter and specifically neuronal connectivity is thought to play a crucial role in the central processing of fatigue and it is a disabling complication of white matter disease. Also, it is also known, that patients with white matter disease as well as diabetes are more prone to excessive sleepiness as well as day sleepiness. However, this presence of excessive sleepiness is not there in non-diabetics. As your father is having white matter disease as well as diabetes, therefore he is sleeping more particularly during day time. There is no known cure for white matter disease. Still, physiotherapy by trying to make balance while standing or walking etc., adequate treatment of accompanying diseases particularly of hypertension and diabetes as well as stopping smoking, having a healthy life style by nutritious diet and possible gradually increased graded exercises may be helpful. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Satnarain Bansal, General & Family Physician