Normal people who sleep with their heads tilted back do not suffer from insufficient blood supply. However, suffering from cervical spondylosis, carotid artery stenosis, heart disease and other underlying diseases may lead to insufficient blood supply to the brain. Under normal physiological circumstances, sleeping in a sitting position or lying down with the head tilted up will not cause insufficient blood supply to the brain and other parts of the body, and the heart, blood vessels, and organs can coordinate with each other to ensure the blood supply to each organ so that it can work normally. But sleeping in a sitting position with the head tilted up for a long time, for patients with cervical spondylosis, it is easy to aggravate cervical spine injury, displacement, compression of the spinal cord, blood vessels or nerves resulting in cervical spondylosis, which will cause insufficient blood supply to the brain. If in pathological conditions, such as suffering from carotid artery stenosis or heart disease and other underlying diseases, sleeping with the head back for a long time is likely to cause poor blood flow and insufficient blood supply, inducing cardiovascular and cerebrovascular diseases. It is recommended that people try to lie down flat to rest, and if various discomforts occur, consult a doctor in time.