Just passing by, I thought I’d add my experience...
I’ve been on Niacin + magnesium malate in the evening for over 3 months now and it still works like a charm to fall asleep quickly when I wake up during the night.(I may use melatonin sometimes to falll asleep, but usually I feel tired a few hours after the niacin/mg combo).
I once ran out of magnesium malate so switched to magnesium citrate, and I woke up a lot more, then couldnt fall asleep again after 5-6 hours of sleep. Added malic acid that I had in my bag of tricks and got my usual better sleep.
So, Niacin on its own is not enough for me, but once I have the magnesium it does help me fall asleep quickly. I did not get this with magnesium alone.