“With few exceptions over the past half century, every experiment that has investigated the impact of deficient sleep on the human body has observed an overactive sympathetic nervous system. For as long as the state of insufficient sleep lasts, and for some time thereafter, the body remains stuck in some degree of a fight-or-flight state. It can last for years in those with an untreated sleep disorder, excessive work hours that limit sleep or its quality, or the simple neglect of sleep by an individual.”