Regarding their health, every horses are not equal at birth. Jumping has an impact on horses health, if they don't have a really good health, with the rhythm of showjumping competitions, they can have localised injuries.
I am very careful with that, whether it's at home or at shows. As my vet says, horses are not made to land on one finger, so joints and ligaments are sorely tested.
If a horse is well trained, there will be less repercussions, but we still see many horses who are stopped during the season because of their health. There's a turn over during the season, which are longer than before, without any winter break. There are also more riders, so you need to go fast, to take tight turns, so good joints are needed.
It's more demanding for high level horses, but also for amateur level horses. We are more likely to dammage our horses by going fast.