Who is most likely to experience nasal regurgitation?

The answer is young child.

Nasal regurgitation it's when the food regurgitates out of the nose.

This is more likely to occur in babies / young children with some birth defects in the soft palate, or if they have a cleft lip. Those birth defects, usually, get fixed with surgery when they are still children, that's why is less frequent after that age.