Abstract: Objective:To analyze the correlation of obesity degree with serum neuropeptide Y(NPY) level in patients with obstructive sleep apnea hypopnea syndrome(OSAHS),its influence on OSAHS disease and night change of the NPY level,and provide the theoretical basis for the clinical treatment of OSAHS.Methods:Patients aged from 40 to 65 years old were divided into OSAHS group(140 cases) and non-OSAHS group(35 cases).According to the body mass,the OSAHS group were further subdivided into the mild obesity group,moderate obesity group,severe obesity group and normal body mass group(35 cases each group).The breath disorder index and lowest oxygen saturation(LSaO₂) in all cases were recorded using the night polysomnogram evaluation for at least 7 hours.The body weight,body mass,neck circumference and ratio of waist to hip of all cases were analyzed.Results:The serum NPY levels of OSAHS patients in obesity group were higher than that in non-OSAHS group and mild OSAHS group(P<0.01),and which in severe OSAHS group was higher than that in moderate group and mild group(P<0.01).Among the OSAHS patients,the NPY level was positively and negatively correlated to the breath disorder index and body mass coefficient,respectively(P<0.01).The NPY level in OSAHS patients was negatively and positively correlated to the neck circumference and ratio of waist to hip,respectively(P<0.01).Conclusions:The serum NPY level in OSAHS patients is correlated to the severity of OSAHS and obesity degree,and which increases with the aggravating of OSAHS severity.