I finally went through the article i posted the link for in the title post (thanks me for posting it!) and I'm glad I did - I found the last two paragraphs of the discussion part particularly interesting:
The present results suggest that with respect to a bacterial challenge, a presumed immune-supportive function for NREM sleep may be restricted to conditions of subtle host defense stimulation, for example, during the very early stages of infection.
In conclusion, the present study demonstrates that human sleep-wake behavior is very sensitive to host defense activation, probably via an endotoxin-induced release of inflammatory cytokines. These cytokines promote deep NREM sleep amount and intensity if the activation is subtle or leads to considerably disrupted sleep when a stronger activation occurs.