The data shows that there is a correlation between city size and REM sleep. Las Vegas is an outlier, but we can all expect that: Who is in Las Vegas to sleep! REM sleep is important to our sleep cycle because it stimulates the areas of your brain that are essential in learning and making or retaining memories. The importance of REM sleep, in particular, is attributed to the fact that during this phase of sleep, our brain exercises important neural connections which are key to mental and overall well-being and health. According to the National Institute of Neurological Disorders and Stroke, <//www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding-Sleep> a study depriving rats of REM sleep significantly shortened their life span, from two or three years to five weeks. Rats deprived of all sleep cycles lived only five weeks.