Linda Lusic Kalcina, Ivana Pavlinac Dodig, Renata Pecotic, Maja Valic, Zoran Dogas Department of Neuroscience, Split Sleep Medicine Center, University of Split School of Medicine, Split, CroatiaCorrespondence: Zoran DogasDepartment of Neuroscience, Split Sleep Medicine Center, University of Split School of Medicine, Soltanska 2, Split 21000, CroatiaTel +38521557905Fax +38521557955Email zdogas@mefst.hrPurpose: Determinants of obstructive sleep apnea (OSA) are hypoxemia and hypercapnia, as well as (micro) arousals from sleep, resulting in chronic sleep fragmentation, sleep deprivation, and excessive daytime sleepiness (EDS). All of the above-mentioned factors might contribute to psychomotor impairment seen in OSA patients. Additionally, this study aimed to assess the contribution of BMI, age, EDS assessed with Epworth sleepiness scale (ESS), and severity of OSA assessed with apnea-hypopnea index (AHI) to the reaction time on chronometric tests in OSA patients and controls. It is hypothesized that moderate and severe OSA have adverse effects on reaction time of perception to visual stimulus, of solving simple arithmetic operations, and of psychomotor limbs coordination assessed by chronometric psychodiagnostic test battery.Patients and Methods: This study was conducted on 206 male participants; 103 of them had moderate or severe OSA diagnosed by whole-night polysomnography/polygraphy. Control participants (N=103), matched to patients with OSA by age and BMI, had no reported OSA in their medical history, no increased risk for OSA, nor EDS. All participants were assessed with three chronometric psychodiagnostic tests, measuring thereaction time of perception to visual stimulus, of solving simple arithmetic operations, and of psychomotor limbs coordination.Results: Participants from theOSA group achieved impaired results compared to control participants in minimum single task solving time in speed of solving simple arithmetic operations (3± 0.9 and 2.6± 0.6, P< 0.001), and in minimum solving time of a single task in complex psychomotor limbs coordination (0.69± 0.2 and 0.61± 0.1, P=0.007). Regression analysis revealed no significant contribution of daytime sleepiness to the results achieved in each of the tests.Conclusion: It is concluded that severe OSA impaired speed of perception, convergent, and operative thinking. Moreover, it is suggested that EDS did not contribute to poor psychomotor outcome in patients with OSA in thisstudy, when age was controlled for.Keywords: obstructive sleep apnea syndrome, overnight polysomnography, psychomotor performance, psychodiagnostic test, daytime sleepiness