Both HDAC1 gene (2.06 ± 2.33 versus 1.09 ± 0.88 fold change, adjusted p = 0.022; Fig. 2A) and HDAC1 protein (1.58 ± 1.94 versus 0.61 ± 0.43 ng/μl, adjusted p = 0.001; Fig. 2B) expressions were significantly higher in OSA patients than that in PS subjects, while HDAC1 gene expression was significantly reduced after more than 6 months of CPAP treatment in 8 selected OSA patients (1.38 ± 1.52 versus 5.96 ± 3.08 fold change, p = 0.017; Fig. 2C). This evidence concerns the gene HDAC1 and obstructive sleep apnea syndrome.