 The investigators recruited both male and female sedentary individuals between 40 to 65 years from sleep laboratory that had recently performed sleep study. All non-menopause women were studied between the first and the fifth day after the onset of menstruation, since hormonal variability during the regular menstrual cycle may affect blood pressure BP or stress perception. Hypertension was carefully excluded in the groups. All subjects had at least three office BP measurements made by one of the study investigators, in addition three out of office BP measurements. Study subjects who had a body mass index BMI 30 kgm2, cardiopulmonary disease, chronic renal disease, diabetes mellitus, atrial fibrillation, pacemaker, hypertension, renal failure, echocardiographic evidence of impaired left ventricular function ejection fraction 45, history of psychiatric disorders, dementia or other neurodegenerative disorders, a history of smoking or alcohol abuse 2 or more drinks per day, any sleep apnea treatment, story of circadian desynchrony e.g. shift workers, incomplete 2 years of formal education, resting blood pressure lower than 14090 mmHg, body mass index BMI greater than 30 kgm2. The study was approved by the institutional committee on human research and all subjects gave written, informed consent. 