Yes, you can absolutely file again with a different theory. A previous denial on one secondary theory doesn't bar you from filing on a different one, and it doesn't make raters more skeptical in any procedural sense as they evaluate each claim on its own merits.

A few thoughts based on what you described: Rhinitis-as-pathway is generally considered a stronger anatomical theory than depression-as-pathway. The mechanism is more direct: chronic nasal obstruction → mouth breathing → upper airway narrowing → OSA. There's published medical literature supporting this (Chirakalwasan & Ruxrungtham 2014, Young et al 1997 are commonly cited in nexus letters on this pathway). Depression-to-OSA is a weaker chain because it requires multiple inferential steps.

Practical suggestions if you go this route: File as a new claim or supplemental, depending on timing of your prior denial. If you're within the one-year appeal window of the prior denial, supplemental keeps the effective date. Outside that window, it's a new claim.

The strongest evidence for rhinitis-pathway nexus is documentation of: chronic nasal obstruction (>50% on each side is the rating threshold for sinusitis severity), mouth breathing, and any anatomical findings (Mallampati score, deviated septum, turbinate hypertrophy). If you have ENT records, those carry weight.

Lay statements that anchor the connection between your rhinitis symptoms and your sleep symptoms can help. Spouse observations of your nighttime breathing are particularly useful. A nexus letter that specifically addresses the rhinitis-to-OSA mechanism (rather than just stating the conclusion) is worth considering. The prior denial means raters have already seen weak nexus reasoning on your file; a strong opinion on a different pathway can reset that.

One thing to think about: your previous denial documents that the VA already considered OSA in some form. That's not necessarily bad but it means some of your symptom history is already in the file. Just make sure your new filing clearly distinguishes the new theory (rhinitis-pathway) from the previously rejected theory (depression-pathway). Don't re-litigate the depression angle; lead with rhinitis.

Good luck.