Athletes are more likely to die of heart failure than a sedentary person at a young age.
Yes. They are able to do a higher performance in physical tasks, but high level elite athletes train up till the edge of what their bodies can sustain. They are at a higher risk of heart failure and their immune system is usually weakened.
Doing moderate sports is healthy, but extremes are never good for your body, neither being an extreme couch potato nor being an extreme athlete.