Why it suits older dogs
Scent work asks for thinking, not speed. A dog can search at a walk, or lying down, or from a soft bed. There is no jumping, no hard stops, and no need for strong eyesight or hearing. That makes it open to many dogs who have given up other games.
Mental work can also help keep an older dog engaged. We cannot promise it will slow aging, and the research on that is still limited. What we can say is that a dog who has a job tends to look brighter and more interested in the day. For a general guide to changes in older dogs, see senior dog behavior changes.
Most important, begin with a visit to your vet. Ask about arthritis, vision, heart, and any other concerns. If your dog has a condition that limits activity, ask what level is safe.