Megadosing D3 on the rare occasion is similar to gradually taking normal amounts as far as serum levels go. It's common to see in studies. You wanna be careful doing it without supervision obviously but I don't see why there would be a difference in a study if the hypothesis is that deficiency is causing the sleep problems.
As far as the study goes, it was significant at a p 0.05 level so will wait for replication.
As far as the study goes, it was significant at a p 0.05 level so will wait for replication.