Sleep Stage Scoring

The original Rechtschaffen and Kales sleep scoring manual of 1968, commonly known as the “R and K” rules, was used until 2007 at which point the American Academy of Sleep Medicine (AASM) updated the scoring manual in what is commonly known as the AASM Scoring Manual. The Rechtschaffen and Kales method divides sleep into five distinct stages (Table 1): non-rapid eye movement (non-REM) stages 1, 2, 3, and 4 and stage REM sleep (stage R sleep). The AASM Scoring Manual recognizes four sleep stages (Table 2): stage N1 (formerly stage 1 sleep), stage N2 (formerly stage 2 sleep), stage N3 (formerly stages 3 and 4 sleep), and stage R sleep (formerly stage REM sleep). The reader is reminded that sleep stages should not be viewed as distinct entities, but rather as a gradual transition of a waveform. The scoring rules were devised to allow for uniformity between sleep laboratories and offer a conceptual simplicity rather than a rigid framework.