Sleep apnea hypopnea syndrom(OSAHS)is a sleep disorder that can cause systemic multi-system dysfunction,and can be fatal in severe cases.Homocysteine(Hey)is a sulfur-containing amino acid,Hey level is closely related to cardiovascular disease,hypertension,inflammation,cancer,metabolism and so on.Numerous studies have shown that OSAHS can cause changes in Hey levels,and the study of key enzyme genes MTHFR and MTRR related to folate metabolism may provide a theoretical basis for the correlation and possible mechanisms between OSAHS and Hey.A systematic review of relevant literature both domestically and internationally is conducted,focusing on the current research status of the impact of OSAHS on Hcy,as well as the effects and possible mechanisms of MTHFR and MTRR,in order to provide further theoretical basis for future research on OSAHS.