Under 38 CFR 3.310, a disability that is proximately due to — or aggravated by — a service-connected condition is itself service-connected. This is the largest category of missed claims, because the second condition often develops years later and does not feel connected to service at all.
Frequent secondary pathways
- Sleep apnea secondary to PTSD or to allergic rhinitis
- Hypertension secondary to PTSD or obstructive sleep apnea
- GERD secondary to long-term NSAID use for service-connected pain
- Depression secondary to chronic pain or functional loss
- Opposite-side knee or hip strain secondary to altered gait
- Radiculopathy secondary to a service-connected spine condition
Causation versus aggravation
Two different arguments are available, and a strong opinion usually addresses both. Causation says the service-connected condition brought the second condition into existence. Aggravation says the second condition existed independently but was made permanently worse. Aggravation claims are rated on the increment of worsening, so establishing the baseline severity matters.