Sleeping with an open mouth in the elderly may be due to physiologic factors, respiratory obstruction, respiratory infections, and other factors. 1. Physiological factors: with age, the elderly body muscle relaxation, may easily lead to respiratory obstruction during sleep, it can be open mouth breathing. 2. Respiratory tract obstruction: usually associated with a variety of factors, such as chronic tonsillitis, sinusitis, pharyngitis, etc., may lead to upper respiratory tract obstruction, and when they sleep with poor breathing, they may open their mouths to breathe. 3. Respiratory infections: for example, bronchitis, etc., may lead to a decrease in ventilation, and will open the mouth to breathe during sleep, which helps to improve ventilation as well as hypoxia. Elderly people who sleep with their mouths open, and with other abnormalities, should also consult a doctor for examination and treatment, to avoid delays in the condition.