Fatigue is a problem in all areas of transportation, production, law enforcement & armed services where a (in theory) a 30 hr day exists. In my past there has been the situation (very early 70s and overseas) of 70+ hr duty (operational management not flying) with only snatched 60 min naps. Yes excessive, but we had to keep the operation going, the attitude was the Spanish, French & Greek ATCOs who were on strike, were not gonna stop us flying!
Whether it is 12 or 8 hr shifts, the switch from days to nights or from lates to earlies (8 hr T/R incorporating the commute) leaves folks fatigued, this is accumulative, and insidious in it's effects on qualitative output.