Grantland recently published this article, Mere Mortals, which claims that:

Baseball players who accrued at least five qualifying seasons from 1959 through 1988 died at a higher rate than similarly experienced football players from the same time frame.  The difference between the two is statistically significant⁶and allows us to reject the null hypothesis; there is a meaningful difference between the mortality rates of baseball players and football players with careers that emulated the [National Institute for Occupational Safety and Health] NIOSH criteria.

The authors then go on to collect data on football and baseball players who played at least 5 years between 1959 and 1988, and their results are below:

From this table, to their credit, they calculated confidence intervals for the mortality rate, as well as performing a fisher exact test to test for independence between the rows (dead or alive) and columns (baseball and football). For football players, the 95% confidence interval for the mortality rate was (11.6, 13.9), and, for baseball players, the 95% confidence interval was (14.1,17.8).  The Fisher exact test gives a p-value of about 0.004 and from this they conclude, correctly, that the mortality rate is significantly different between the groups at the 0.01 level.

So, the big question is, as they pose it:

Why is it that baseball players from the ’60s, ’70s, and ’80s are dying more frequently than football players from the same era? Truthfully, as a layman, I can’t say with any certainty, and I don’t think it’s appropriate to speculate. A deeper study into the mortality rates of baseball players that emulated the NIOSH focus on specific causes of death versus the general population might prove valuable.

Well, I’ll “field” (pun intended) this one.  Baseball players are dying more often because they are older that football players.  The authors, as far as I can tell, never controlled for the age of the players, or any other risk factors for that matter. In 1959, there were, as far as I can tell, 12 NFL teams each with 40 players.  That 480 players.  In 1988, there were 28 teams with 59 players each; A total of 1652.  In baseball, in 1959 there were 16 teams with, let’s use the largest number, 40 man teams, for a total of 640 players.  That number in 1988 was 1040 (26 teams with 40 players).  So there were almost 3 and half time more players in the NFL in 1988 than there were in 1959.  The number of baseball players only increased about 1.6 times over this same period.

These numbers aren’t exact, but the point still stands:  The group of football players that has been collected here has a greater proportion of younger people in it than the baseball group.  So it’s not exactly apples to apples.  In fact, it’s not even close.  You’d expect, just based on the ages of the players in these groups for baseball players to have higher rates of mortality than the football players.  So basically they have demonstrated that the old die more often than the young.

Cheers.

P.S. My first boss once gave me this example.  Remember the ad where it was claimed that 90% of all trucks sold in the last ten years were still on the road?  You’re comparing cars that are ten years old in the same group with cars that are less than a year old.  Not exactly apples to apples.