From the article:
> Non REM Stages 1 and 2: Light sleep NREM-sleep
> Non REM Stages 3 and 4: Deep slow wave sleep (SWS)
> REM-sleep when dreams occur
> FFI patients cannot go past stage 1
It appears they are getting sleep, but only stage 1 sleep. That might be what keeps them alive for 9 months. If stage 1 was blocked, I venture to guess their survival duration would be much lower.