Possible reasons for feeling breathless while sleeping are as follows: 1. Functional diseases, such as anxiety, depression, neurosis, etc. can cause breathlessness and organic diseases must be excluded before diagnosis. 2. Respiratory diseases, such as lung infections, bronchial asthma, chronic obstructive pulmonary disease, etc. can cause breathlessness and are sometimes severe at night. 3. Cardiovascular diseases, such as various cardiac arrhythmias and heart failure can cause chest tightness and breath-holding. These patients are mostly combined with cardiovascular risk factors, such as combined hypertension, diabetes, hyperlipidemia, obesity, smoking, etc. In addition, there are other diseases that can cause breathlessness, but a comprehensive medical history and systematic ancillary examinations are needed to determine the cause, and then effective treatment measures are taken to address the cause.