Sleep is essential to our health and humans should spend a third of their lives asleep. As everyone can attest, even one sleepless night can make us feel awful. In the US, one-third of adults, and an even greater proportion of teens and minority populations, do not get the seven hours of sleep per night recommended for healthy adults. This has led the CDC to declare lack of sleep a public health epidemic. Sleep is a non-negotiable bodily function characterized by a lack of consciousness, inhibited sensory activity, and cessation of voluntary muscle movement. Though our bodies do not move much during sleep, the brain is highly active. We cycle through sleep stages, including rapid eye movement (REM) and non-rapid eye movement (NREM) sleep, which are defined by unique electrical activity signatures in the brain. We cycle through these stages several times each night with increasingly longer REM periods occurring towards the morning. Many cues orchestrate your sleep timing and need including your internal circadian rhythm, neuronal signals and hormones, metabolism, temperature, light exposure, and food patterns.

We know sleep is the only universal animal behavior, but why we sleep remains one of the most perplexing unanswered questions in biology. Recent studies have suggested that sleep promotes energy, consolidates memory and learning, promotes connections between neurons, and clears the brain of metabolic waste and toxins. These activities help restore the body’s systems and functions. Despite these advances, we don’t really know why we sleep, and even less is known about sleep’s impact on disease. While many clinical studies have convincingly shown that lack of sleep increases the risk of diseases including cardiovascular disease, Alzheimer’s, cancer, diabetes, and autoimmune disorders, the cellular and molecular mechanisms that underlie these associations remain unclear.

Sleep disorders, including insomnia, hypersomnia, narcolepsy, and sleep apnea, are common and often undiagnosed. Many people without a sleep disorder often have sleep routines that have negatively impact their health. Night shift workers and people consistently exposed to jet lag have trouble maintaining regular sleep hygiene which can have detrimental effects on their health. People often sleep less on weekdays and more on weekends, but this ‘social jet lag’ can also negatively impact health and wellbeing.

A better understanding of why we sleep and its consequences on health will lead to changes in public policy and encourage people to adopt healthier sleep habits.