Abstract: Objective: To explore the impact of obstructive sleep apnea hypopnea syndrome on body immune function and inflammatory reaction by analyzing the changes of peripheral blood lymphocyte immunophenotype and C-reactive protein (CRP) in obstructive sleep apnea hypopnea syndrome(OSAHS) patients.Methods: According to the results of polysomnography test,60 subjects diagnosed with obstructive sleep apnea hypopnea syndrome were divided into mild OSAHS group(20 cases),moderate OSAHS group(22 cases) and severe OSAHS group(18 cases),and 40 subjects without OSAHS were selected as control group.The age,sleep patterns and peripheral blood oxygen content during sleeping period of all subjects were compared.Double fasting blood was drawn in each subject which was used to analyze lymphocyte immunophenotype by flow cell meter and check blood CRP values.Results: Average blood oxygen content and lowest blood oxygen content in OSAHS patients were significantly lower than those in controls,there had the statistical significances of the degree of decline of blood oxygen among the different degree OSAHS groups (P<0.01).Peripheral blood CD3⁺,the ratios of CD4⁺/CD3⁺ and CD4⁺/CD8⁺ in OSAHS patients were significantly lower than those in controls(P<0.05 to P<0.01),there had the statistical significances among the different degree OSAHS groups (P<0.01).The ratio of CD8⁺/CD3⁺ in OSAHS patients was significantly higher than that in controls(P<0.05 to P<0.01).The percentage of CD16⁺ CD56⁺ lymphocyte in OSAHS patients was higher than that in controls(P<0.05).There were no statistical significance of CD19⁺ lymphocyte percentage between OSAHS patients and the controls(P>0.05).Peripheral blood CRP value in severe OSAHS patients was increased,compared with that in mild OSAHS patients and the controls(P<0.01 and P<0.05).Conclusions: OSAHS decreases immunity function of the body and activates inflammation reaction,which was associated with the severity degree of OSAHS.