What percentage of my sleep should be REM?

Healthy adult men should spend approximately 20–25% of total sleep in REM (1.5–2 hours for 7–8 hours of sleep), unlike deep sleep, REM is relatively preserved until age 60, making it less clinically urgent than declining N3 in men aged 40–55 (Ohayon et al., Sleep, 2004).

REM sleep serves memory consolidation, emotional processing, and certain aspects of hormonal regulation (particularly cortisol preparation for morning). The pattern of REM distribution across the night is important: REM cycles are shortest in the first half of the night and longest in the final 2 hours before waking, which is why cutting sleep short by even 60–90 minutes disproportionately eliminates REM. The most clinically pressing sleep architecture problem in men 40–55 is not REM loss, it is deep sleep loss. Men who are focused on their REM percentage while ignoring their N3 deep sleep percentage have the clinical priority backwards.

Honesty Scale: Solid (1) for REM normative data and its preservation in middle age relative to deep sleep.

What to do: Protect the last 90 minutes of your sleep window, this is your highest-REM sleep time. If you consistently wake before an alarm cuts through this window, the quality of your REM sleep is better than if you are alarm-dependent. Alcohol, while sometimes increasing sleep pressure, dramatically fragments and reduces REM sleep.

For the full picture, read The Sleep Architecture Deep Dive