Making the milk thicker, in order to make it harder to reflux, has a long history in the treatment of GE reflux, or spitting-up babies. As I mentioned in a previous post there are some thickeners that have been associated with NEC, specifically xanthan gum.
In general, in good studies, the effects of thickeners have been modest or absent, in terms of reducing reflux. One group has previously studied Gaviscon, which is an alginate that sort of clots in the stomach, so reducing reflux. They showed that it did reduce reflux, but did not reduce apnea.
The most recent study from that same group looked at the effects of another agent, amylopectin. They again showed in a small cross-over RCT that thickening reduced reflux (in this case acid reflux but not non-acid reflux) but did not reduce apnea, the most parsimonious explanation for this is that reflux has nothing to do with apnea.
That is exactly the interpretation that Christian Poets puts on the data in his accompanying editorial .
In fact Corvaglia and colleagues are the only group that has consistently shown a relationship between reflux and apnea. If you look at their data closely, it appears that the apneas that they find after feeds more than between feeds, and that they seem to show are associated with reflux on Multi-luminal impedance monitoring, are short apneas of 5 seconds or more. It does not appear that pathologic apneas, with associated hypoxia and bradycardia are associated, even in their studies. Maybe this is the difference to other investigators, and the reason why those others, who only looked at longer, pathological apneas, have not found any association.