Inclusion Criteria:  age at least 16 during tonsillectomy preoperative obstructive sleep apnea and AHI (apnea-hypopnea index) > 14 tonsillectomy has been done because of the symptoms caused by tonsillar hypertrophy (ICD-10 diagnostic codes G47.3, R06.5 or J35.1) in addition to tonsillectomy, patients may have undergone shortening of uvula and/or radio frequency ablation of soft palate  Exclusion Criteria:  AHI < 14 in addition to tonsillectomy patient has undergone uvulectomy, uvulopalatoplasty, uvulopalatopharyngoplasty or mandibular advancement other, evaluated by investigator