Definitely something to think about and it doesn't necessarily apply only to the elderly.
As I mentioned in my Turneffe Island trip report, one of the guests there, probably in his early 40's, slipped at the top of the outdoor stairs that go up to the second floor of the Lodge. He tumbled all the way down, about 10 or 12 steps in all. It had been raining, and these stairs were definitely slippery when wet. I didn't see it happen, but I was told he was carrying something in both hands so he didn't have a hand free to grip the railing.
Big, big mistake.
This was early in the week, and we didn't see him again until the week was almost up. The general consensus was that he had probably broken a rib in addition to full body bumps and bruises. Had it been much worse, I'm sure the management would have taken him back to the mainland for medical attention. As it was, per his wife he went straight to bed and could hardly move the first few days so she would take him his meals. The poor guy still wasn't much better when the week was up, although he finally made it to the pool the night before we left.
That was one dive vacation that went down the toilet in a flash.