By far the most commonly studied health outcome involving data from the MLB is mortality. The first analysis of MLB mortality was published in 1975 in the Statistical Bulletin of the Metropolitan Life Insurance Company.(1) This study, which was conducted in the days before personal computers, drew upon the vital status of over 10,000 baseball players from the 1974 Baseball Encyclopedia. Using these data, the authors calculated standardized mortality ratios (SMRs) using US general population mortality rates as a baseline. In comparison to the US general population, players whose careers began between 1876 and 1900 experienced only 97% of the expected mortality, those who debuted between 1901 and 1930 experienced only 64% of the expected, and those who debuted between 1931 and 1973 experienced only 55% of the expected deaths. As early as the 1930s, Major League baseball players were exhibiting the healthy worker effect and/or the health benefits of the rigorous fitness regimen of professional athlete.
