Sleep cycles: how a night is structured

A night's sleep is not uniform. It runs in cycles of roughly 90 minutes, each moving through lighter and deeper non-REM stages and then into REM.

The important part for dreamers is that the proportions change across the night. Deep non-REM sleep dominates the first half; REM periods get longer as the night goes on. The final REM period before waking can run 45 minutes or more.

What follows from that

• Your most vivid, most narrative dreams are usually the last ones. They are also the ones you are most likely to remember, because you woke from them.
• Cutting sleep short cuts REM disproportionately. Losing the last 90 minutes of an eight-hour night removes a large share of the night's dreaming.
• Waking mid-cycle rather than at the end of one is part of why some mornings feel so much worse than others.

Why this matters for the journal

If you want to remember more dreams, the highest-leverage change is usually not a technique. It is sleeping long enough to reach the late REM periods at all. The pattern dashboard plots recall against sleep duration for exactly this reason.