Chronic bad breath may be due to a variety of reasons. If it is caused by periodontitis, it may be related to the occurrence of cardiovascular and cerebrovascular diseases, respiratory diseases, digestive diseases, etc., as follows. 1. Cardiovascular diseases: periodontitis may cause acute or subacute infective endocarditis, in addition, periodontitis is a risk factor for coronary heart disease and its acute attacks. 2. Respiratory diseases: periodontal infection is associated with aspiration pneumonia and chronic obstructive pulmonary disease, and oral anaerobic bacteria are often detected in aspiration pneumonia and lung abscess. 3. Digestive system diseases: Helicobacter pylori in periodontal pockets can enter the digestive tract and cause chronic gastritis and gastric ulcer. Long-term bad breath may also lead to other diseases, it is recommended to go to the hospital in time to receive early treatment.