Sleeptracker-AI data reveals a correlation between city size and REM sleep duration — larger cities are associated with less REM sleep on average. Las Vegas is a predictable outlier: it records among the lowest REM sleep of any city in the dataset, consistent with its reputation as a destination where sleep is not the priority.

The implications are significant. REM sleep is the stage during which the brain consolidates learning, forms and retains memories, and maintains the neural connections essential to cognitive and emotional health. According to the National Institute of Neurological Disorders and Stroke <https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Understanding-Sleep>, research depriving rats of REM sleep reduced their lifespan from two to three years down to five weeks. The cognitive and physiological stakes of REM deficiency are well established.

That city size emerges as a correlate of REM duration in a dataset of this scale points to the cumulative effect of urban environments on sleep architecture — noise, light pollution, later social schedules, and longer commutes among the likely contributing factors.