Patients with obstructive sleep apnea syndrome (OSAS) have a morphological and functional abnormality of the upper respiratory tract, and the obesity of these patients is the main cause for OSAS. Obese patients with OSAS are closely associated with life-style related diseases and metabolic syndromes. The circulatory system is most strongly influenced by OSAS and hypertension, cerebrovascular disease and cardiovascular disease are the prime complications of OSAS. A psychosomatic approach is required for the treatment of OSAS in patients with obesity. The pathophysiology of upper airway resistance syndrome (UARS) is similar to OSAS in that there is abnormal airway resistance in the upper airway during sleep, but UARS does not meet the diagnostic criteria of OSAS. UARS should be classified as a separate syndrome or as part of the larger group of sleep-disordered breathing (SDB). Patients with UARS have a clinical condition that differs from that of patients with OSAS and resembles the condition of patients with functional somatic syndrome (FSS). We sometimes find slightly lower levels of night arterial saturation in patient with unidentified somatic symptoms. This is also found in patients with UARS. It is necessary to examine the respiratory events of patients with FSS and unidentified somatic symptoms during sleep.