Why do professional athletes have a shorter life expectancy on average than the general population?
There are two main reasons. The first is wear and tear on the body. The extreme physical stress over time takes its toll. Imagine you have two shoes that are identical. One, you wear everywhere, running and hopping and walking on it everywhere. The other, you wear only for special occassions. Which one will wear out faster? The other reason has a bit to do with biochemistry. Your professors stats are correct–but oddly only for male athletes. The reason has to do with testosterone. This male hormone is a steroid. Steroids are widely known to negatively effect the body. Consider that athletes on average have higher levels of testosterone than other people. So on top of being the perpetually worn shoe, there is also a chemical that is eating away at the lining. I hope that answers the question.
