Background:Obstructive sleep apnea syndrome (OSAS) is a disease with increasing prevalence,which is mainly characterized by increased cardiopulmonary mortality and morbidity.It is well-known that OSAS patients have increased prevalence of cardiovascular diseases including coronary heart disease,heart failure,and arrhythmias.The aim of this study was to evaluate the presence of prolonged and fragmented QRS complexes,which have previously been associated with cardiovascular mortality,in OSAS patients.Methods:Our study included 51 patients (mean age 41.6 ± 10.1 years) who were recently diagnosed with OSAS (apnea-hypopnea index [AHI] ≥5 events/h) and never received therapy.The control group consisted of 34 volunteers (mean age 43.1 ± 11.6 years) in whom OSAS was excluded (AHI ＜5 events/h).The longest QRS complexes was measured in the 12-lead electrocardiogram (ECG) and the presence of fragmentation in QRS complexes was investigated.Results:Fragmented QRS frequency was significantly higher in patients with OSAS (n =31 [61％] vs.n =12 [35％],P =0.021).QRS and QTc durations were also significantly longer in OSAS patients than controls (99.8 ± 13.9 ms vs.84.7 ± 14.3 ms,P ＜ 0.001;411.4 ± 26.9 ms vs.390.1 ± 32.2 ms,P =0.001,respectively).Analysis of the patient and controls groups combined revealed a weak-moderate correlation between AHI and QRS duration (r =0.292,P =0.070).OSAS group had no correlation between AHI and QRS duration (r =-0.231,P =0.203).Conclusions:In our study fragmented QRS frequency and QRS duration were found to increase in OSAS patients.Both parameters are related with increased cardiovascular mortality.Considering the prognostic importance of ECG parameters,it may be reasonable to recommend more detailed evaluation of OSAS patients with fragmented or prolonged QRS complexes with respect to presence of cardiovascular diseases.