Recently, my dad and I went to Sun Valley, Idaho for a ski trip. Both of us, every night that we were there, had extremely vivid dreams. Vivid dreams and poor sleep at high altitudes are somethings that are frequently reported by mountain climbers (Thompson, 2007). What is it about high altitudes that cause such vivid dreams?
At high altitudes the air is thinner and less oxygenated and periodic breathing occurs. Periodic breathing is the alternating of deep and shallow breathing, or even a complete pause in breathing following deep breathing (Thompson, 2007). This alternation of breathing patterns contributes to the insufficient amount of oxygen that already exists at high altitude, causing bodily tissues to receive less oxygen than normal and affecting both breathing and sleeping. More specifically, it causes one to experience a decrease in sleep efficiency, reduced total sleep time, slow wave sleep and REM sleep (Lemos et al, 2012). The reduced slow wave and REM sleep may be what causes the vivid dreams, but how this happens remains unanswered.
During slow wave sleep a person is in their deepest sleep and their brain slows, becoming less responsive to external stimuli, while during REM sleep a person is dreaming (Harvard Medical School, 2007). Many people are able to better recall their dreams when they awake from REM sleep; it is like they are waking up in the middle of a dream so the dream is readily available to their consciousness. It is possible that at higher altitudes the cycles of sleep happen quicker so we are more likely to wake up during a bout of REM sleep, and therefore more likely to recall our dream. It could also be that the decreased oxygen levels somehow affect our dream recall, making dreams seem more vivid. Even another possibility is that the decreased amount of slow wave sleep, proposed to have the function of consolidating memories from the day, leads the brain to try to make-up for that loss of consolidation through vivid, realistic, dreams. Any of these ideas could be the reason that dreams are reported as more vivid at high altitudes, but these ideas are simply ideas and need to be investigated for their validity.
Lemos, V. A., Antunes, H. K., Santos, R. V., Lira, F. S., Tufik, S., & Mello, M. T. (2012). High altitude exposure impairs sleep patterns, mood, and cognitive functions. Psychophysiology, 49(9), 1298-1306.
Natural Patterns of Sleep. (2007, December 18). Healthy Sleep. http://healthysleep.med.harvard.edu/healthy/science/what/sleep-patterns-rem-nrem.
Thompson, A. R. Sleep at High Altitude. Altitude.org. from http://www.altitude.org/sleep_at_high_altitude.php.