Low oxygen at altitude causes pauses in breathing during sleep, called central sleep apnea. Central sleep apnea causes repeated awakenings and poor sleep. Low oxygen itself and the induced oxidative stress can damage mental function which is likely worsened by poor sleep. Reduced mental function due to low oxygen can pose a serious danger to mountain climbers. However there is also mounting evidence that even in populations of people that live at high altitudes and are considered adapted, low oxygen contributes to reductions in learning and memory. Therefore there is a serious need for treatments which may improve sleep, control of breathing and mental function during low oxygen. Melatonin is a hormone produced in the brain during the night which regulates sleep patterns with strong antioxidant and anti-inflammatory properties. A study previously reported that melatonin taken 90 mins before bed at 4,300 m (14,200 ft) induced sleep earlier, reduced awakenings and improved mental performance the following day. However how melatonin caused these effects was not determined. Therefore this study aims to determine how melatonin effects control of breathing, sleep and mental performance during exposure to low oxygen.

Inclusion Criteria:

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Exclusion Criteria:

• Sleep disorders
• Pregnant females
• Smokers (quit ≥ 1 year ago acceptable)
• Any known cardiac (apart from treated hypertension with acceptable drugs, see below), pulmonary (including asthma), renal, neurologic (including epilepsy), neuromuscular, hepatic disease, or patients with diabetes.
• Prior or current use of melatonin.
• Use of any medications that may affect sleep or breathing, blood-thinning medications (anticoagulants), antioxidants, anti-inflammatories, medications that suppress the immune system (immunosuppressants), diabetes medications and birth control pills.
• A psychiatric disorder, other than mild depression; e.g. schizophrenia, bipolar disorder, major depression, panic or anxiety disorders.
• Substantial alcohol (>3oz/day) or use of illicit drugs.
• Previous occurrence of high altitude pulmonary or cerebral edema.
• Recent exposure to altitude (>8000ft) in the last month or having slept at an altitude >6000ft in the last month.
• Inability to provide written informed consent or able to complete the experiment.
• Non-English speakers (necessary to complete neurocognitive testing).
• More than 10 cups of beverages with caffeine (coffee, tea, soda/pop) per day.