The most important factors of gender, BMI, obesity and occurrence of OSA as well as OSA severity in terms of AHI and ODI, distribution of sleepy vs. non-sleepy OSA phenotypes, ESS score and circulating TNF-α levels were similar in both groups, which confidently supports the concept that the current study population was representative of the whole RICCADSA cohort. This evidence concerns the gene TNF and obstructive sleep apnea syndrome.