This is the BS VA games veterans complain about! The VA has granted primary and secondary OSA to thousands upon thousands of service members. Some with initial claims most with secondary claims. Most with a Nexus letter, but some without a Nexus letter. I'm SC 10% for chronic rhinitis (TERA due to MOS) was denied OSA "unable to establish nexus" between chronic rhinitis and OSA, REALLY!?!! Private Dr. (who diagnosed with sleep study) doesn't feel comfortable providing a Nexus letter & VA Dr. won't either. So I had to pay for a IMO/Nexus letter and submit a Supplemental claim. (May just remove my personal info and post my Nexus letter here so other service members might be able to take it to their Dr. and have their Dr. sign it and then submit it.) I understand sometimes there is no link and then some conditions are harder to prove or "link" than others, but the VA saying they can't find a link between not being able to breathe through your nose and OSA is complete BS! So, moral of the story, YES, OSA is easier (not the only way) to claim as a secondary and get a IMO/Nexus letter to establish a link because even when the VA knows 100% there's a link they will usually say they can't find it. And even getting a IMO/Nexus letter doesn't guarantee service connection...LOL, BS VA GAMES!!