Objective:To observe the diurnal changes of serum hypoxia inducible factor-1α (HIF-1α) and its relationship with polysomnography (PSG) parameters in obese patients with obstructive sleep apnea (OSA).Methods:In this study, 64 obese subjects with OSA (experimental group) and 24 normal subjects (control group) were included. PSG monitoring was performed in all subjects, and peripheral blood samples were collected at night and next early morning to detect the expression level of HIF-1 α mRNA and protein concentration in serum. The data were analyzed by SPSS25.0 software. The counting data was represented by n(%), and t-tests were used for inter group comparisons. The measurement data of normal distribution adopted mean ± standard deviation ( ± s), and the inter group comparison adopted Chi-square. Serum HIF-1α mRNA levels and protein concentrations in the two groups were compared and analyzed by Two-way ANOVA, and Spearman rank correlation was used to analyze the correlation. Results:The ratio of male to female in the control group was 15: 9 and the average age was (39.25 ±10.58) years old, while that in the experimental group was 41∶24 with an average age of (41.31 ±15.20) years. The body mass index (BMI) of experimental group was higher, while all the relevant parameters recorded by PSG were significantly different between two groups ( P<0.001). The results showed that there was no significant difference in the expression of HIF-1α mRNA between the control group and the experimental group ( P=0.914), or between night and morning ( P=0.167). The concentration of HIF-1α protein in the control group was significantly lower than that in the experimental group ( P<0.001), but there was no significant difference in the concentration of HIF-1α protein in the same group at night and in the morning ( P=0.798). The results of correlation analysis showed that there was a significant correlation between PSG related indexes(AHI, minimum blood oxygen, mean blood oxygen and SIT90), night and morning mRNA expression and protein concentration ( P<0.05). Conclusions:Compared with normal people, the concentration of serum HIF-1 α protein in obese patients with OSA is higher, but there is no difference between night and morning. The process of HIF-1 α induced by CIH may be involved in post-translational regulation rather than transcription, and other compensatory mechanisms may also be involved.