Evaluation of relationships between hepatic steatosis and sleep apnea in subjects suspected to have abdominal obesity, and effects of CPAP treatment on hepatic steatosis

INTERVENTION: CPAP (Continuous Positive Airway Pressure) CONDITION: obstructive sleep apnea, hepatic steatosis PRIMARY OUTCOME: CT attenuation of liver INCLUSION CRITERIA: (1) Evaluation of relationships between hepatic steatosis and sleep apnea # Those who underwent polysomnography for suspicion of sleep apnea, and underwent abdominal CT at the time of polysomnography or before the introduction of CPAP (The target sample size is 200). (2) Evaluation of effects of CPAP on hepatic steatosis # Those who were introduced CPAP therapy for diagnosis of obstructive sleep apnea by the polysomnography described above. # Those who were diagnosed to have abdominal obesity at the baseline evaluation. # Six months or more elapsed from the introduction of CPAP.