Noradrenergic Dysregulation, Sleep and Cognition in Older Adults With Insomnia

Inclusion Criteria: 1. Age ≥ 55 years; 2. Independent in activities of daily living and without clinically significant cognitive impairment as determined by a mini-mental status examination (MMSE) score ≥ 26; 3. Due to the effect of reproductive hormones on autonomic regulation, sleep and cognition, women will be postmenopausal; 4. time spent in bed not greater than 8.5 hours; 5. Sedentary, defined as participation in exercise of moderate intensity for less than 30 minutes per day and less than two times per week on a regular basis. 6. average daily light exposure indicative of indoor environments (from questionnaire). Inclusion criteria for the insomnia group: 1. Meet criteria for chronic insomnia disorder according to the International Classification of Sleep Disorders (3rd Ed.); 2. Subjective sleep efficiency less than 85% and/or awakening earlier than desired if before 6 AM for ≥3 nights/week in the previous 4 weeks; 3. Subjective WASO (sWASO) ≥ 60 minutes for ≥3 nights/week in previous 4 weeks. sWASO will include time spent awake after sleep onset before final awakening + time spent awake in bed attempting to sleep after the final awakening; 4. global PSQI score greater than 5; 5. average daily light exposure indicative of indoor environments (from questionnaire). Inclusion criteria for the control group: 1. No history of chronic or short-term insomnia disorder according to the International Classification of Sleep Disorders (3rd Ed.); 2. Subjective sleep efficiency greater than 85%; 3. Subjective mean total sleep time of 6.5 hours to 8 hours; 4. Habitual bedtime of 9PM-midnight; 5. PSQI score ≤ 5. Participants in the control group will be matched with the insomnia group on sex and age (±3 years). Exclusion Criteria: 1. Sleep disorders other than insomnia (restless legs syndrome, parasomnias, REM behavior disorder, circadian rhythm sleep-wake disorder, sleep apnea by STOP questionnaire and apnea hypopnea index (AHI) ≥ 15 by home sleep apnea test; 2. habitual bedtime before 9pm or morning awakening before 5am; 3. History of neurological disorders; 4. History of psychiatric disorders; 5. A Beck depression inventory ((BDI-II) score greater than 19); 6. Unstable or serious medical conditions; 7. Prediabetes and diabetes (HbA1C ≥ 5.7) 8. Current, or use within the past month, of psychoactive, hypnotic, stimulant or analgesic medications (except occasionally); 9. Use of medications that interfere with NA system activity including B-blockers, selective serotonin and norepinephrine reuptake inhibitors (SNRIs) and selective norepinephrine-dopamine reuptake inhibitors (NDRIs); 10. Hormone replacement therapy; 11. Use of medications that affects pupil diameter and responses to light (i.e. antihistamines, anticholinergics, benzodiazepines, narcotics for pain; 12. History of visual abnormalities that may interfere with pupillary responses to light exposure such as significant cataracts, narrow-angle glaucoma or blindness; 13. History of heart conditions (i.e. arrhythmia, coronary artery disease, angina, heart failure); 14. Shift work or other types of self-imposed irregular sleep schedules; 15. BMI \> 35 kg/m2; 16. History of habitual smoking (6 or more cigarettes/week) or caffeine consumption \> 400 mg/day. 17.Use of weight-loss medications