Sorry to pick the academic scab here, when the first thing that's worth considering is that hey, football does take years off your life (though your plea for a balanced approach is appreciated.) In the same spirit, here's a little more of the financial landscape.
It's support for the theory of "they had the money to live longer" (very broad strokes description), that they all played 5 years or more. IOW, they weren't 1-year washouts technically in the league on someone's practice squad, they had legit NFL careers. Just picking a random year in there, 1981, the average salary in the NFL was about $91,000 (really quaint low number by today's standards.)
The NFL's average salary in 1981 increased by 14.5 percent over 1980 to $90,102, according to the annual salary survey conducted by the league's Management...
www.upi.com
In a "That can't be right" moment, the average salary in 1981 for all occupations was 47,700. Wow, it only doubled your income to be a pro football player in 1981! Of course, you got double the average income at a very young age, by definition. 40 was an ancient warrior then, and in the main, still is now.
Social Security Administration Research, Statistics, and Policy Analysis
www.ssa.gov
But still - double the income is a huge apples-to-oranges comparison. (It would be less so in the earlier cohorts, with 1981 pay representing, say, guys born 1959 and earlier. Guys born in 1938 would not vary as much from the mean income. Guys born in 1967 getting paid in 1988, well, couldn't make the 5-year requirement. So really the skew might be more in 1984 than 1981, continuing to the 1988 skew. But I have to sit up a half hour for the statin to settle, so let's look.
1984 league average, $162k
1984 average overall, $48,211
National Football League players made more money in 1984 than ever, according to a listing of salaries compiled by the NFL PLayers Assn. and published Sunday by the Dallas Morning News.
www.latimes.com
By 1988, the fifth year of the last cohort included in the study, it was
1988 average salaries by team - lowest (TB), $178,300; highest (SF), 280,400
1988 average overall, $50,538
So, on the 49ers, in 1988, you were making an average of between 5 and 6 times the national average.
My point in trotting out this factor is that apples-to-apples would really be closer if you compared to the average man making twice to nearly six times the mean income, for the 80s up to 1988. And I am sure that earlier there were still benefits to being a pro athlete - it was just a percentage multiplier over the average income, not a multiplier of several times the income (quickly ballooning to orders of magnitude difference.)
And even being solidly in the desireable high-income group, these guys were losing years off their life expectancy against the national average.