My Dad's job made him so physically sick that he had to retire at age 54. He was a tool grinder in an auto plant before they wore any protective equipment so got emphysema so bad that he couldn't walk a block or tighten his wheel at work to grind tools anymore. He had no strength left at all. He worked right up until it was not physically possible anymore. He was able to get SSDI and collect his 30 year pension early because of his disability.