Dierdre taking a nap at midday gave me every day a ld for years, besides the ones i got at night. These days i dont nap at midday.

Your melatonin level shifts over the 24 hours cycle of day and night and prob at midday and such its way lower then at night, so you wont really sleep deep when u take a nap at day time.
Also you already have been awake for hours so its a sort of time relayed wbtb tech!
But to simply answer your question, you sleep lighter so more awareness in your sleep, closer to waking and there for more chance on lds.

Jeff