The sleep cycle is typically broken up into four stages: three stages of non-REM sleep and one final stage of REM. Stage 1 typically lasts no more than several minutes long – the average is about 14 minutes. Stage 2, light non-REM sleep, is the longest phase. Stage 3 is deep sleep, or “slow wave sleep”. The final, fourth stage is REM sleep, which first occurs about 90 minutes into the sleep cycle and is associated with greater brain activity. Snoring typically occurs in the last two stages.
After the REM stage, the cycle begins again with stage 2, and the brain activity begins to slow back down into deep sleep in stage three.