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The overactive bladder is a symptom complex characterized by urgency, frequency and nocturia. The etiology is believed to be multifocal and evidence supporting abnormality of central ner-vous system control of the bladder has been re-ported. Some investigators suggest that abnormal micturition reflex may be a cause of OAB. This is normally initiated when the bladder is sufficiently full or when the intraluminal pressure is suffi-ciently high. These parasympathetic afferent and efferent systems are very important to control bladder. So OAB patients without proven other etiology such as urinary tract infection may have some disturbance in bladder controlled by para-sympathetic nervous system. HRV is a non in