Effects of Melatonin on Sleep, Ventilatory Control and Cognition at Altitude
Effects of Melatonin on Sleep, Ventilatory Control and Cognition at Altitude
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.Therefore this study aims to determine how
 melatonin effects control of breathing, sleep and mental performance during exposure to low
 oxygen.
Research has shown that exposure to low oxygen at altitude causes neurocognitive impairment
 (impaired mental processing, memory, attention, learning, etc). This impairment in cognitive
 performance poses a serious risk to mountain climbers and while it has traditionally been
 thought that people who live at high altitude have adapted to it, evidence shows there is
 still considerable damage to the brain and impairments in cognitive function of people who
 live and work at high altitude.

 As every cell in the body requires oxygen to survive and function, impairment in cognitive
 performance at altitude is thought mainly due to reduced oxygen availability to the central
 nervous system. However, low oxygen at altitude also causes unstable breathing during sleep
 which results in short periods where the brain stops sending the signal to breath, called
 central sleep apnea (CSA). During apneas (pauses in breathing) blood oxygen drops even lower
 and people typically wake up briefly and hyperventilate after apneas. Therefore at altitude
 people usually get less sleep, their sleep is broken with periods of wakefulness during the
 night and they experience repeated bouts of severe low blood oxygen levels. Sleep plays a
 critical role in how the brain repairs and also converts newly acquired information into
 long-term memory. Therefore broken and reduced sleep can impair cognitive performance, memory
 and learning. Repeated bouts of severe low oxygen also produces highly reactive molecules
 that cause damage to cells, called oxidative stress. Oxidative stress also prevents the brain
 from forming long-term memories and in severe cases (such as extremely high altitude and long
 duration exposure) can cause neurons in the brain to die. Therefore although sustained low
 oxygen at altitude likely impairs cognitive function, disturbed sleep and repeated bouts of
 severely low oxygen likely also contribute to causing brain damage and impaired cognitive
 performance.

 Melatonin is a hormone produced in the pineal gland of the brain during the night which
 signals to the brain that it is time to sleep. Melatonin is also a very powerful antioxidant
 which naturally helps to prevent damage in the body from oxidative stress. A study previously
 reported that melatonin taken 90 mins before bed at 4,300 m (14,200 ft) reduced the time
 taken to fall asleep, it reduced the number of times people woke up during sleep and improved
 cognitive performance the following day. However how melatonin caused these effects was not
 determined. Therefore this study aims to determine how melatonin affects ventilatory control,
 sleep and neurocognitive performance during sustained hypoxia.
Inclusion Criteria:

 -  Healthy Males and Females

 -  Age:18-65 years

 Exclusion Criteria:

 -  Sleep Disorders

 -  Pregnant Females

 -  Smokers (quit ≥ 1 year ago acceptable)

 -  Cardiovascular, Pulmonary, Renal, Neurologic, Neuromuscular, or Hepatic Issues

 -  Diabetes

 -  Psychiatric disorder, other than mild depression

 -  Recent exposure to altitude (>8000ft) in the last month or having slept at an altitude
 >6000ft in the last month