Demencia literally translates to "dementia", the medical condition affecting memory. It's a very rare and powerful word to find in a song.
In "Pasado", the singer uses it metaphorically, singing "Sufro demencia para olvidarme / Lo mucho que te quería" (I suffer from dementia to forget / How much I loved you). He wishes for this condition to erase the painful memories of a lost love, showing the extreme depth of his heartbreak and making this a truly unforgettable lyric.
Ever had an ex pop back into your orbit, and suddenly your brain tries to erase months of crying? That is the exact delusion Venezuelan singer Carmen DeLeon and Cali Y El Dandee lean into on "Pasado". The chorus chases pure fantasy: holding someone close while dancing ("Bailando a tu lado / Así abrazados" [Dancing by your side / Hugged like this]) and pretending that the lonely nights are gone forever ("Las noches tristes / Quedaron en el pasado" [The sad nights / Stayed in the past]). The narrator wants to fool themselves into believing the breakup never even happened, just like their partner promised ("Como me lo prometiste" [Like you promised me]).
Then the verse drops the daydream and hits you with brutal honesty. Cali Y El Dandee's part admits that hiding the truth ruined everything: "Yo por estúpido no fui sincero" (I, like an idiot, wasn't honest). He even compares the emptiness to a calendar running backwards, asking what it feels like to live through "un diciembre que me sabe a enero" (a December that tastes like January to me), turning the warm festive season into cold post-holiday reality. He jokes about needing medical intervention—"Cuanta anestesia debo tomarme / Para no sentir esta herida" (How much anesthesia should I take / To not feel this wound)—to numb the regret. It is a sharp, catchy track about wanting to hit the rewind button, even when you know you messed up.