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.
MUSINGS - REVELATIONS - REVIEWS
A Majorly Unique Occupational Cohort
Occupational epidemiology seeks to identify hazardous exposures in the workplace using various methods of research. The gold standard for such research is the occupational cohort study, in which workers are enrolled and followed throughout their career in an industry and beyond, if possible.
Some of the major challenges for any cohort study are selection bias and incomplete follow-up. This is indeed a poignant issue in occupational epidemiology as incomplete record keeping can make cohort enumeration difficult and workers can easily be lost when they leave employment.
An ideal occupational cohort would have several key characteristics:
1. A complete listing of all the workers who ever worked in the industry (at least during a substantially long study period);
2. Complete work-history information for each of these individuals, including hire and separation dates and time spent at various positions;
3. Complete vital-status for all members throughout the study period;
4. Extensive accrued follow-up time spanning a long period;
5. A solid and reliable exposure measure;
6. A low-cost to collect, process, and analyze the data
Seldom does something real come close to an ideal, but for once we have one: Major League Baseball (MLB).