It can feel almost like a sexual malfunction. You used to want sex more often; now the sofa defeats your erotic life by a landslide.
But desire does not exist separately from the rest of the body. Sleep deprivation affects attention, mood, stress and general wellbeing, while chronic overload means the brain is holding dozens of unfinished tasks for hours. In that state, sexual stimuli are not competing with emptiness — they are competing with everything else that requires resources.
That does not mean every reduction in libido should be explained away as tiredness. Persistent changes can be related to relationships, medication, mental or physical health and may deserve attention in their own right.
But before looking for a complicated explanation, it can be worth looking at the conditions under which the body is being expected to produce desire.
If the only realistic opportunity to want sex arrives at 11:47 p.m. after six hours of sleep the night before, perhaps libido has not announced its death after all. Perhaps it just wants to sleep.