Changes to human sleep architecture during long‐duration spaceflight.

Summary Both rapid eye movement and non‐rapid eye movement sleep are important for cognitive function and well‐being, yet few studies have examined whether human sleep architecture is affected by long‐duration spaceflight. We recorded 256 nights of sleep from five crew members before (n = 112 nights), during (n = 83 nights) and after (n = 61 nights) ~6‐month missions aboard the Mir space station, using the Nightcap sleep monitor. We compared sleep outcomes (including total sleep time, efficiency, latency, rapid eye movement and non‐rapid eye movement) during spaceflight with those on Earth. We also evaluated longitudinal changes over time in space. We found that wakefulness increased by 1 hr in space compared with on Earth. Over time in space, rapid eye movement was initially reduced and then recovered to near preflight levels at the expense of non‐rapid eye movement sleep. Upon return to Earth, sleep architecture returned to preflight distribution. Our findings suggest that spaceflight may alter sleep architecture and should be explored further. [ABSTRACT FROM AUTHOR]