Common causes and risk factors of stroke in young people Young stroke is a stroke that occurs in young people under 35 years of age. According to a domestic epidemiological survey, young people account for 9.77% of all strokes, mainly ischemic strokes, with a male predominance. The incidence of ischemic stroke in young people has been increasing recently, and early detection of the cause of stroke in young people is very important for prevention and treatment. In this paper, the common causes and risk factors for stroke in young people are reviewed as follows. Most scholars believe that the main cause of stroke in young people is atherosclerosis. The literature reports that young stroke patients with no clinically apparent cause but with different types and degrees of proximal plaque on cerebral arteriography may be considered to be due to atherosclerosis. Kitter SJ et al. found that atherosclerosis of the large arteries accounted for 3.8% of all first-episode strokes in 428 young patients, often with carotid or basilar artery stenosis, thus pointing to atherosclerosis as the most important cause of intracranial artery stenosis. 2. Non-atherosclerotic vascular lesions 2.1 Interstitial aneurysm is formed when blood penetrates into the head and neck vessels to the subintima of the blood vessels and then extends longitudinally along the long axis of the vessels for a distance between the vessel walls. It is often accompanied by a longitudinal extension of the vessel wall for a distance and is often accompanied by tearing of the intima. The literature reports that this disease accounts for 26% of stroke patients under 35 years of age and that the most common cause of cervical vessel entrapment aneurysms is trauma. In addition, the connective tissue disease Elhers-danlons disease type IV also predisposes to the development of entrapment aneurysms. 2.2 Moyamoya disease is also known as smoker’s disease and anomalous vascular network disease of the brain base. The etiology of this disease is unclear, and both congenital and acquired evidence have been found. The disease is most common in Asia, mostly in Japan, and often involves children, young adults, and women. The clinical manifestations of the disease are highly variable, with patients under 20 years of age showing mostly ischemic manifestations, with episodes of limb weakness or hemiparesis, which may alternate between right and left, with recurrent episodes, or may develop from one side to bilateral paralysis. patients over 20 years of age have a high prevalence of subarachnoid hemorrhage, which is due to increased proximal pressure after vascular occlusion, which can easily rupture the fragile and thin-walled collateral circulation network or small penetrating vessels. Cerebral arteriography is the most reliable diagnostic method, and the combined use of MRI and MRA can better identify the accompanying vascular network as well as small foci of infarction within the deep penetrating branches of the blood supply. 2.3 Takayasus arteritis is also known as primary or nonspecific aortitis, aortic arch syndrome, and pulselessness. It is common in Orientals and young women, with a high incidence in the national population. The disease is a chronic progressive inflammatory disease of the aorta and its main branches due to an autoimmune reaction. Stenosis or occlusion of the affected arteries can cause damage to the heart, lungs, brain, spinal cord, kidneys, digestive system, and surrounding tissues and organs. Clinically, ischemic cerebrovascular disease can manifest as TIA, cerebral infarction, lacunar cerebral infarction, and watershed infarction. Through clinical analysis of 38 cases of young cerebral infarction patients, Yu-Mao Li found that cerebral arteritis narrowed or occluded blood vessels leading to cerebral infarction and caused stroke in young people, indicating that cerebral arteritis may be a causative factor of stroke in young people. 2.4 Fibromuscular developmental abnormalities The pathology of this disease is characterized by abnormal development of blood vessels, a congenital mesodermal disease, mostly seen in female patients with degeneration of vascular smooth muscle and fibroblasts, segmental stenosis and dilatation of arteries, fiber proliferation under the intima and epima of the stenotic part of the artery, and muscle thinning or disappearance of the dilated part, weak fiber dissection, and easy complication of aneurysm. The cerebral arteriogram has a characteristic presentation: (1) typical bead-like changes in the arteries; (2) stenosis with or without constriction and aneurysmal dilatation in the stenotic segments; (3) diverticulum-like, smooth or wrinkled pockets in the arterial wall with non-circular damage. Cerebral arteriography should be routinely performed in young and middle-aged stroke patients with hypertension, especially in young women with unexplained headache, tinnitus, vertigo, arrhythmia and syncope. Nagaraja et al. study confirmed that respiratory tract infection in young stroke patients is common with Streptococcus pharyngeus haemolyticus. Cardiac disease Cardiogenic strokes are more common in young people with stroke. The literature reports that cardiac strokes account for 11.5% 25.8% of strokes in young people from all causes. In the past, rheumatic heart disease was the most common cause of stroke. In the last decade or so, with advances in prevention and treatment, the incidence of rheumatic disease has declined, and valvular disease, patent foramen ovale, and arrhythmias are the most common causes of cardiac stroke. Stroke can be caused by atrial wall thrombosis and platelet hypercoagulation in mitral valve prolapse, as well as by concomitant bacterial endocarditis and arrhythmias. Foramen ovale insufficiency accounts for approximately 35% and 45% of cardiogenic strokes in young people. 4.1 Antiphospholipid antibody syndrome is a group of clinical syndromes characterized by recurrent habitual abortions, thrombocytopenia, reticulocytosis, recurrent venous thrombosis and positive antiphospholipid antibodies (APL). Bokristensen et al. found that 4.7% of young stroke patients had increased APL in their blood. 4.2 Platelet abnormalities can cause bleeding due to abnormal platelet quality and quantity and increased capillary fragility, as well as microthrombosis due to abnormal platelet aggregation and release of reactive substances, which can progress to thrombosis. 4.3 Patients with sickle cell anemia contain abnormal hemoglobin S in their red blood cells, which can block microcirculation and cause infarction. 4.4 Protein C and protein S deficiency Protein C system is an important natural anticoagulation system in the body to balance the coagulation process and prevent thrombosis. 5, migraine headache Migraine headache causes vasospasm, platelet hyperfunction and increased blood viscosity, increasing the risk of stroke, with infarction of the posterior cerebral artery being the most common. 6, Hyperhomocysteinemia Hyperhomocysteinemia (HCY) is an independent risk factor for cerebrovascular disease. An epidemiological study involving 1200 cases and corresponding controls showed that mild to moderate HCYemia significantly increased the risk of cerebrovascular disease and was positively correlated with the severity of stroke. 7.1 Oral contraceptives 7.1 Estrogen in oral contraceptives can affect the metabolism of sugar and fat and increase blood lipids, which can increase the blood clotting factors and blood viscosity, resulting in a hypercoagulable state of blood and causing stroke. 7.2 The mechanism of pregnancy is vasospasm and hypercoagulability, which leads to ischemic stroke, accounting for 5% of all strokes in young people. The risk of stroke in pregnant and perinatal women has been reported to be 13 times higher than in the same age group. Whisnane MD et al. analyzed the incidence and risk factors of stroke in young people by counting all hospitalized patients with cerebral infarction and found that the risk factor with the highest incidence was smoking. Alcohol abuse is another risk factor for stroke in young people. A survey of patients aged 16-40 years with first-ever ischemic stroke showed that alcoholism and occasional alcohol abuse were equally likely to cause ischemic stroke, and that ingestion of more than 40 g of ethanol within 24 h before the onset of stroke was a trigger factor. 7.4 Genetic factors Developments in molecular genetics, particularly in the area of hereditary cerebrovascular disease associated with stroke in young people, have provided a new basis for diagnosis and prevention of stroke in young people. Studies have shown that the influence of genetic factors is more important in young stroke patients. Traditional risk factors for ischemic stroke such as hyperlipidemia, obesity, hypertension, and diabetes mellitus also play an important role in the development of ischemic stroke in young people, and their prevention and control measures are gradually gaining attention. In conclusion, the risk factors for stroke in young people are complex and diverse, and effective prevention and treatment of the causes and risk factors is necessary to reduce the incidence of stroke in young people and improve their quality of life.