Ferric reducing ability of plasma (FRAP) before and after polisomnography controlled sleep. Closed circles – evening (before polisomnography controlled sleep). Open circles – morning (after polisomnography controlled sleep). Results of FRAP in 27 subjects with OSAS expressed as mean and standard deviations represent the concentration of Fe3+ reduced ions after 0, 1, 2, 3, 4, 5, 6, 7 and 8 min incubation of patient plasma sample with the FRAP reagent. No significant differences (p > 0.05) were found for evening and morning FRAP at all incubation time-points.