Early wake-up times could harm health, sleep doctors say

Sleep experts told Fox News Digital that forcing an earlier wake time can reduce REM sleep and leave people fatigued and mood‑unstable; they noted chronotype is partly inherited, around 40–50 percent.

Many people try stricter morning routines at the start of a new year, but sleep doctors say an early alarm is not suitable for everyone. Experts told Fox News Digital that whether someone is a morning person or a night owl depends on their chronotype, which influences when deep and REM sleep occur. People cycle through sleep in roughly 90‑ to 110‑minute periods, with deep NREM sleep concentrated earlier in the night and more REM sleep later. Forcing a substantially earlier wake time can reduce REM sleep and leave some people feeling persistent fatigue and mood instability, the experts said. Key points: - Sleep occurs in repeated cycles of about 90 to 110 minutes that alternate between deep NREM and REM sleep. - Deep NREM sleep is more common earlier in the night and supports physical repair, immunity and memory, while later REM-rich cycles support learning and emotional regulation. - Chronotype — whether someone naturally rises early or late — is described by experts as partly inherited, estimated at about 40–50 percent. - Forcing an earlier wake time often reduces REM sleep and has been associated by experts with feelings of being "wired but tired," mood instability and longer‑term metabolic and mental health risks. - Experts reported measures they use to shift sleep timing or protect sleep quality, including consistent schedules, morning bright light and wind‑down routines before bed. Summary: Experts said overall health and daytime functioning relate strongly to sleep consistency and quality rather than simply rising earlier. They noted that social schedules often favor earlier wake times, which can conflict with biological clocks. Undetermined at this time.