Introduction: obstructive Sleep Apnea Syndrome (OSAS) is a serious confition that compromises the quality of life and survival of patients. Its main risk fator in adults is obesity and the gold standard test for diagnosis is polysomnography (PSG), mainly through the apneia-hypopnea index (AHI). Objective: to analyze the sleep pattern of obese patients with indication for bariatric surgery, determining the main polisomnographic parameters compromised by obesity. Methods: This work is a

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... ional study with analysis of polysomnography perfomed in patients with obesity in the peroperative period of bariatric surgery at a clinic in Vitória da Conquista/BA during 2017. The Epi Info 7 platform was used for analysis of the data. Results: 58 polysomnographic reports were analyzed, with 56,9% morbdly obese and 43,1% non-morbid. The prevalence of OSAS was 70,68% and de AHI ranged from zero to 84,6 with a mean of 19,47±22,89 e/h. morbidly obese, compared to "non-morbid", had a longer saturation time below 80% and 90% (0,4±0,93 vs. 0,12±0,45 e 4,87±7,38 vs. 1,36±2,87 respectively; p-value=0,02 in both), worse index respiratory disorders ((29,24±25,36 vs. 16,88±16,21; p-value=0,02), higher AHI (24,71±25,68 vs. 12,56±16,67; p-value=0,02), higher hypopnea index values (16,41±17,10 vs. 6,99±8,52; p-value=0,006) and lower minimum saturation (78,24±9,80 vs. 85,24±6,33; p-value=0,004). Conclusions: the high prevalence of OSAS found confirms its indication in the preoperative period of bariatric surgery. The main respiratory event involved in most individuals with OSAS was the hypopnea index.