Abstract： Objective To observe the change of patients with obstructive sleep apnea hypopnea syndrome (OSAHS) whose cognitive function and serum advanced oxidation protein (AOPP) levels,and analyze its correlation.Methods Sixty-seven patients with OSAHS (OSAHS group),of the Department of Respiration of First People's Hospital of Yancheng in 2013 were the sequence included,there were 49 cases of men patients,18 cases of women patients,they were from 21 to 67,average ages were (44 ± 9).At the same period,20 healthy volunteers were selected as (control group),there were 14 men,6 women,A BMI and the general situation of two groups were matched,they were given respectively polysomnography (PSG) monitoring,according to the sleep apnea index (AHI),were divided into mild to moderate and severe.Epworth sleepiness scale (ESS) was applied,Mini Mental State Examination (MMSE) and clock drawing test to evaluated the degree of daytime sleepiness and cognitive function,and detected serum oxidative stress indices AOPP,superoxide dismutase (SOD) and the levels of malondialdehyde.In group OSAHS,15 cases were given continuously positive airway pressure (CPAP) treatment (treatment group).and observed the changes of above indexes before and after treatment.Results Compared with the control group,MMSE and the clock drawing test score of OSAHS group and treatment group were lower.Compared with the severe OSAHS group,MMSE,clock drawing test scores of treatment group increased.MMSE score of OSAHS group whose attention,computing power,memory (especially shortterm memory) was significantly reduced respectively [(4.73±0.81)-(2.69± 1.38) and (2.85±0.61)-(1.92±0.62)].Compared with the control group,serum AOPP and MDA levels of OSAHS group and treatment group increased,were separately [(78± 20)-(117 ± 20) μmol/L and (2.9 ± 1.0)-(6.1 ± 3.0)μmol/L],and reduced levels of SOD [(89± 8)-(57 ± 9) U/ml].Compared with the severe OSAHS group,serum AOPP,malondialdehyde levels decreased,the level of SOD increased.All subjects (OSAHS group and treatment group,did not include a control group,the same below) MMSE,clock drawing test score and PSG related index (SaO2,the lowest SaO2,AHI based,LA/HT,SLT90 ％) were related to,they had statistical significance.The serum levels of AOPP,MDA,SOD level and MMSE,clock drawing test score related,serum levels of AOPP and MDA,SOD correlation,the difference has statistical significance.Conclusions Patients with OSAHS whose cognitive dysfunction is related to the severity of symptoms,and the main performance is for the short term memory capacity and computing ability damage.AOPP is a sensitive index to reflect the early oxidative protein damage in patients with OSAHS,and is closely related to cognitive dysfunction.