Sleep is not a luxury, it is a biological necessity.

That is the central message of Matthew Walker, the neuroscientist and author of the bestselling book Why We Sleep. Walker, who directs the Center for Human Sleep Science at the University of California, Berkeley, has spent decades studying how sleep affects the brain, body, and long-term health.

According to Walker, quality sleep is as important as duration. The body cycles through two critical stages: non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep. NREM sleep supports physical repair, immune strength, and stress recovery, while REM sleep is essential for memory, learning, emotional regulation, and creativity. Missing either stage weakens the brain’s ability to function optimally.

To improve sleep quality, Walker emphasizes consistency above all else. Going to bed and waking up at the same time every day helps stabilize the body’s internal clock, or circadian rhythm. Irregular schedules, even sleeping in on weekends, can leave the brain in a constant state of jet lag.

He also advises limiting stimulants like caffeine and nicotine, especially in the afternoon and evening, and avoiding alcohol close to bedtime. While alcohol may make you feel drowsy, it suppresses REM sleep and causes fragmented rest.

Evening habits matter. Heavy meals, intense workouts, and prolonged screen use before bed can keep the brain alert when it should be winding down. Walker recommends creating a pre-sleep routine that includes dim lighting, relaxation, and time away from electronic devices. Exposure to natural sunlight during the day, particularly in the morning, also helps regulate sleep patterns.

Perhaps most importantly, Walker warns against lying awake in bed for long periods. If sleep does not come after about 30 minutes, it is better to get up briefly and return only when drowsy, so the brain continues to associate the bed with rest.