Hormonal Mechanisms of Sleep Restriction - Axis Study in Older Men and Postmenopausal Women

Inclusion Criteria: * Men or postmenopausal women aged 60-80 years * Willingness to provide written informed consent * Stable weight over preceding 6 weeks * Body Mass index (BMI) 22-28 kg/m2 * Physically and psychologically healthy * Good habitual sleep with regular bedtimes * Neither extreme morning- nor extreme evening-type using Horne-Ostberg Morningness-Eveningness criteria Exclusion Criteria: * Medications that interfere with the adrenal or gonadal axis will be excluded * Unable or unwilling to provide IRB (Internal Review Board)-approved informed consent * Clinical disorders and/or illnesses * Current medical or drug treatment, as assessed by questionnaire * History of brain injury or of learning disability * Vision or hearing impairment unless corrected back to normal * Anemia (Hct \<38%) * History of psychiatric illness * Clinically significant abnormalities in blood and urine, and free of traces of drugs * Other endocrine abnormalities including hypothyroidism or adrenal failure; primary gonadal disease as indicated by serum LH (luteinizing hormone) or FSH (follicle stimulating hormone) concentration \>10 or \>15 IU/L, respectively, hyperprolactinemia indicated by prolactin \>25ug/L * Type 2 Diabetes (HgbA1C) * Current smoker * Recent or concurrent drug or alcohol abuse * Blood donation in previous eight weeks * Travel across time zones within one month of entering the study * Sleep or circadian disorder * Shift work within three months of entering the study * Ir…