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Sleep & circadian

Sleep architecture

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Sleep architecture is how your sleep stages are organized across the night. A typical night runs through four to six 90-minute cycles. Each cycle moves through N1, N2, N3 (deep, slow-wave sleep), and REM. N3 dominates the early cycles; REM stretches out in the later ones. In healthy young-to-middle-aged adults, sleep is roughly 13 to 23% N3 and 20 to 25% REM (N3 falls below 10% by age 70). Normal ranges shift with age, sex, and how sleep is measured. Disruptions to this structure carry real costs. Alcohol suppresses N3, sleep apnea fragments REM, and slow-wave sleep fades with age. Those changes hit memory consolidation, hormone release, immune regulation, and heart recovery, which makes these metrics a key target in longevity-minded sleep assessment.

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Sources

  1. Rechtschaffen A, Kales A. (1968). A Manual of Standardized Terminology, Techniques and Scoring System for Sleep Stages of Human Subjects. *US Government Printing Office*
  2. Moser D, Anderer P, Gruber G et al.. (2009). Sleep classification according to AASM and Rechtschaffen & Kales: effects on sleep scoring parameters. *Sleep*doi:10.1093/sleep/32.2.139