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Nguyen VT, Zafonte RD, Kponee-Shovein KZ, Paganoni S, Weisskopf MG. All-Cause and Cause-Specific Mortality Among Major League Baseball Players. JAMA Intern Med. 2019;179(9):1298–1301. doi:10.1001/jamainternmed.2019.1218
There has been increasing attention to professional athletes’ long-term health. A few studies1-3 reported lower all-cause mortality among Major League Baseball (MLB) players compared with US males, but only 1 study with a small sample (n = 985) examined specific causes of death and reported largely nonsignificant results.3 Players in MLB may have lower cause-specific mortality rates because of fitness associated with playing baseball, but other sport-related aspects—injuries, lifestyle habits, or environmental exposures particular to baseball—could adversely affect players’ health. We recently found lower mortality rates among MLB players overall and for certain specific causes compared with National Football League players, all of whom had playing careers of 5 years or longer.4 To better understand risks compared with the general public, we examined mortality rates among MLB players, including specific causes of death and differences by career length and position.
Players (N = 16 637) appearing in 1 or more MLB game between 1871 and 2006 in the Lahman Baseball Database (http://www.seanlahman.com) were linked with the National Death Index (NDI). Deaths before electronic NDI data in 1979 (n = 5902), deaths outside the United States (n = 90), players without NDI linkage data (n = 135), and players older than 75 years in 1979 without indication of death by the end of follow-up (n = 59) were excluded. The study was approved by the Harvard T.H. Chan School of Public Health institutional review board. Consent was not required because data collection involved decedents; however, a confidentiality agreement was signed with the NDI before the release of data.
Standardized mortality ratios (SMR) adjusted for age, calendar year, and race/ethnicity were calculated to compare MLB players with other US males using the National Institute for Occupational Safety and Health Life Table Analysis System. The at-risk period started January 1, 1979, or at the MLB debut date, whichever was later, and ended at death or the end of NDI follow-up (December 31, 2013), whichever was first. Analyses were performed between January 2016 and March 2019. For comparisons among MLB players by career length and position, hazard ratios from Cox proportional hazards models were calculated using the same at-risk period definition with age as the time scale, stratified by decade of birth, and adjusted for race/ethnicity and body mass index at playing career debut. SAS, version 9.4 (SAS Institute Inc) was used for the analysis.
Among 10 451 MLB players who debuted from 1906 through 2006, 8262 (79.1%) were white, mean (SD) age at MLB debut was 24.3 (2.6) years, and mean (SD) number of seasons played was 6.0 (4.9). Mean (SD) age at death was 77.1 (12.6) years. Compared with US males, the MLB players had significantly lower mortality rates from all causes (SMR, 0.76; 95% CI, 0.73-0.78) and many underlying cause of death categories except neurodegenerative disease (SMR, 0.96; 95% CI, 0.76-1.20) (Table 1). When both underlying and contributing causes of death were considered, statistical significance was met in the same way for all mortality categories. Longer career length was associated with lower all-cause (hazard ratio [HR], 0.97; 95% CI, 0.93-1.00) and cardiovascular-related (HR, 0.91; 95% CI, 0.85-0.96) mortality rates and higher cancer-related mortality rates, particularly lung (HR, 1.13; 95% CI, 0.98-1.31), blood (HR, 1.22; 95% CI, 1.02-1.46), and skin (HR, 1.53; 95% CI, 0.99-2.36) cancers (Table 1). Results were similar when both underlying and contributing causes of death were considered except for digestive tract disease–related mortality (n = 233; HR, 0.94; 95% CI, 0.82-1.09), genitourinary tract–related mortality (n = 279; HR, 0.88; 95% CI, 0.77-1.01), and mortality due to all other causes (n = 83; HR, 0.74; 95% CI, 0.56-0.97).
Compared with pitchers, shortstops and second basemen had lower all-cause (HR, 0.81; 95% CI, 0.72-0.91), cancer-related (HR, 0.78; 95% CI, 0.62-0.98), and respiratory tract disease–related (HR, 0.56; 95% CI, 0.37-0.84) mortality rates; catchers had higher genitourinary tract disease–related mortality rates (HR, 2.52; 95% CI, 1.19-5.35), and outfielders had lower injury-related mortality rates (HR, 0.51; 95% CI, 0.27-0.94) (Table 2). Results were similar for underlying and contributing causes of death together except for in cases of shortstop and second basemen cardiovascular-related (n = 249; HR, 0.87; 95% CI, 0.75-1.00) and injury-related (n = 19; HR, 0.59; 95% CI, 0.36-0.97) mortality rates; there were no significant associations for genitourinary tract–related mortality among catchers (n = 34; HR, 1.19; 95% CI, 0.80-1.77) and injury-related mortality among outfielders (n = 32; HR, 0.80; 95% CI, 0.53-1.20). There were no significant differences in neurodegenerative mortality rate by career length or player position.
Lower MLB player mortality rates may reflect the healthy worker effect among athletes compared with the general population. Lower mortality rates from some causes among players with longer career length may be associated with the sustained fitness required for or other benefits of longer careers. Higher mortality rates from some cancers deserve attention. Skin cancers may be associated with sun exposure, but cancer-related mortality may be associated with products consumed or chemicals (eg, those used to treat fields). Identifying specific factors associated with increased cancer rates may aid in prevention strategies.
Study limitations include the inability to account directly for physical activity, head injuries, and other environmental or genetic factors. Race/ethnicity was imputed for players still alive in 2013; our imputation had good agreement with race/ethnicity when it was known and was consistent with the racial distribution reported in MLB. Mortality rate differences by position may reflect differences in body habitus (eg, middle infielders being leaner). The possible higher genitourinary tract disease–related mortality rate among catchers deserves exploration because genitourinary tract injuries are common in baseball.5 Neurodegenerative mortality rates did not vary by position or career length, nor did they differ compared with the general population. These results contrast with reports among American-style football and soccer players, which could in part be associated with differences in head injury rates by sport.6 The findings suggest that playing in MLB is associated with lower mortality from some diseases, but further exploration of increased cancer rates may be warranted.
Accepted for Publication: March 19, 2019.
Corresponding Author: Marc G. Weisskopf, PhD, ScD, Department of Epidemiology, Harvard T.H. Chan School of Public Health, 665 Huntington Ave, Bldg 1-1402, Boston, MA 02115 (email@example.com).
Published Online: July 22, 2019. doi:10.1001/jamainternmed.2019.1218
Author Contributions: Ms Nguyen and Dr Zafonte contributed equally to the study. Dr Weisskopf had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Concept and design: Zafonte, Weisskopf.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Nguyen, Zafonte, Weisskopf.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Nguyen, Kponee-Shovein, Weisskopf.
Obtained funding: Zafonte, Weisskopf.
Administrative, technical, or material support: Zafonte, Paganoni.
Supervision: Zafonte, Weisskopf.
Conflict of Interest Disclosures: Dr Zafonte reported receiving royalties from Oakstone; serving as coeditor of Brain Injury Medicine; serving as an advisor on the Mackey White Committee, the Scientific Advisory Board of Myomo Inc, Oxeia Biopharmaceuticals Inc, Biodirection, and Elminda Limited; and evaluating patients in the Massachusetts General Hospital Brain and Body Program, funded by the Trust powered by the National Football League Players Association. Dr Paganoni reported receiving grants from Amylyx Pharmaceuticals and Revalesio Corp outside the submitted work. Dr Weisskopf reported receiving grants from the National Institutes of Health and the National Institute for Occupational Safety and Health during the conduct of the study, receiving personal fees from Partners Health Care outside the submitted work, and receiving financial support from the The Spaulding Research Institute. No other disclosures were reported.
Funding/Support: This work was supported in part by the Spaulding Research Institute, grant P30 ES000002 from the National Institutes of Health, and grant T42 OH008416 from the National Institute for Occupational Safety and Health (Ms Nguyen).
Role of the Funder/Sponsor: The funding sources had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.