Jim Irwin, who walked ( and rode a car ) on the moon on Apollo 15, and had some heart problems while on the moon. He was obviously healthy before. He ended up having several heart attacks, and died at age 61. He is an outlier in this regard, and there will always be speculation as to whether the strain of walking on the moon damaged his heart. https://en.wikipedia.org/wiki/James_Irwin

61 is a younger death, but at that age death is very much on the table, statistically speaking - especially back then.

In 1991, when he died, life expectancy for men was 72 years. Meaning for every guy that lived to 83, one guy died at 61.