INS and obstructive sleep apnea syndrome: Continuous positive airway pressure (CPAP) used during night sleep is the first line and most effective treatment for OSA, which has also been proven to positively affect glucose metabolism in obese and nonobese subjects with prediabetes by improving insulin sensitivity and the 24 h blood pressure profile compared to a placebo [102,103], as also shown by a meta-analysis of randomized, controlled trials with a total of ∼240 subjects free of T2DM showing a significantly improved HOMA index after CPAP treatment [104].