Complex sentence: Pavlina was able to continue the experiment for almost six months with apparent ease (save for the initial period of acclimatisation), and mentions only minor permanent side-effects, including being able to fall into sleep very easily when he wishes to.
Split into simpler sentences: Pavlina was able to continue the experiment for almost six months with apparent ease (save for the initial period of acclimatisation). He mentions only minor permanent side-effects, including being able to fall into sleep very easily when he wishes to.