Mortality and Its Risk Factors Among Professional Athletes: A Comparison Between Former NBA and NFL Players

ISBN-13: 9783319772028 / Angielski / Miękka / 2018 / 133 str.

Jeffrey S. Markowitz

Spis treści

*Current chapter names are placeholders only and will be changed for the book

1. Introduction

There are three common factors that can impact on morbidity and mortality among worker groups. First, there are toxic environmental exposures like asbestos or coal dust that can lead to specific types of disease. Second, there are on-the-job dangers that may result in injuries or accidents. In the case of both toxic environmental exposures and injuries or accidents, immediate and/or delayed deleterious health responses can follow. Finally, there are selection factors related to certain occupations like body mass index (BMI), educational level, and lifestyle that may be related to morbidity and/or mortality.

As far as we know, there are not any issues in professional basketball or football with respect to exposure to toxic environmental hazards.

Leisure-time physical activity is thought to have health benefits for participants. When physical activities become competitive and significant physical contact is included in the scenario, the health benefits can become tainted by short- and even long-term injury and illness. In a violent game, like professional football, injuries include concussions and brain trauma that sometimes lead to long-term neurodegenerative illnesses like chronic traumatic encephalopathy (CTE) (Markowitz and Markowitz, 2013, see Chapter 3). While head and other serious injuries do occur in the NBA, no reports of CTE in former basketball players were identified.

Selection factors can also impact on morbidity and mortality, both in the general population and among professional basketball and football players. For example:

• African-Americans live fewer years than whites within the general population (Arias, 2011; Woolf et al., 2004; Satcher et al., 2005), NBA players (Lawler et al., 2016), and NFL players. (Baron et al., 2012; Markowitz, 2016)
  
• People born in the southern part of the US live fewer years than individuals born in other US regions. (Centers for Disease Control and Prevention, 2014) The same is true for NFL players. (Markowitz, 2016)
  
• Obese BMI increases the risk of mortality in the general population (Flegal et al., 2005) as well as within NFL players. (Markowitz, 2016; Baron et al., 2012)
  

In general, less is known about potential risk factors for mortality among NBA players. In addition, mortality and risk factor comparisons have never been made between NBA and NFL players.

2. Literature Review

Three publications written by former National Institute of Occupational Safety and Health (NIOSH) researchers dominate the literature on mortality among former NFL players (Baron et al., 1994; Baron et al., 2012; Lehman et al., 2012). These papers added to existing knowledge at the time that they were written. However, the most recent of these papers is already ten years old and is outdated. In fact, the NIOSH papers only studied relatively young former NFL players (median age = 41 years in the 1994 paper, and 57 years in the two 2012 papers). Consequently, they include relatively small numbers of NFL player deaths (n = 103 and 334 respectively). Since the most recent NIOSH studies, there have been more than a thousand additional deaths among NFL players. Furthermore, the NIOSH studies had significant selection issues based on their sampling of only NFL players with five or more pension-credited playing seasons (from 1959 to 1988). The current book will study all former NFL players who played between 1960 and 1986, and will also study all former NBA players during these same years.

Relevant to the current book, the NIOSH studies reported a mortality advantage for NFL players versus the general population. (Baron et al., 1994; Baron et al., 2012). There is, in fact, a substantial body of scientific literature on mortality and longevity among former elite athletes. Almost all of these papers found that elite athletes lived significantly longer than the general population. Elite athletes identified in published studies include: Finnish male endurance, team, and power sports athletes (Kettunen et al, 2015; Sarna et al., 1997), Norwegian professional divers (Irgens et al., 2013), male members of several Polish Olympic teams (Poznanska and Gajewski, 2001), medal-winning Olympic athletes from nine countries (Clarke et al., 2012), long-term long-endurance cross country skiers (Grimsmo et al., 2011), and French participants in the Tour de France (Marijon et al., 2013). Finally, a meta-analysis that incorporated the results of ten different mortality studies of elite athletes also concluded that these athletes live significantly longer than the general population (Garatachea et al., 2014).

The existing literature on mortality and its risk factors among NBA players is very limited. Lawler et al., (2012) reported that white NBA players lived about 18 months longer than their African-American counterparts in the NBA. While this difference was statistically significant, the gap between the races was much less in these NBA players compared to the gap of 6.1 years reported in whites versus African-Americans in the general population

3. Methods

Study Design: This is a modified retrospective cohort study using high quality published records of former professional NBA and NFL players. Traditional cohort studies often involve comparisons between two groups, one exposed and the other non-exposed, in order to determine how often a specific disease and/or death occur and what the risk factors are. The "exposure" of interest in the current study is participation in one of these two professional sports. The study outcome is mortality (alive or dead). Time to death (longevity) also is evaluated.

Statistical Analysis Plan: The risk factor analyses are conducted within and between NBA and NFL players and are stratified or controlled by year of birth. Odds ratios with 95% confidence intervals are used to identify risk factors for mortality. Survival analyses are used that assess time to death. Players still alive on January 1, 2017 are considered (right) censored observations. Multivariate analyses are conducted in order to identify independent risk factors, and adjusted odds ratios with 95% confidence intervals are provided. When mortality between NBA and NFL players versus the US general population are compared, standardized mortality ratios are calculated that take into account gender, year of birth, and race.

Results

4. Description of Study Cohort

Frequency distributions are provided for all categorical variables and descriptive statistics are given for continuous variables.

Identification of Risk Factors for Mortality

Potential risk factors to be studied include demographics (race and birthplace region), personal factors (BMI), and playing-related variables (player position and years of playing experience).

5. Race

Race data are available for more than 86% of all players in the study cohort. Within players with non-missing race data, there are significantly more African Americans, nearly 65%, in the NBA study cohort versus about 45% in the NFL.

6. Birthplace Region

Players in the study cohort are categorized into one of four US regions based on the states where they were born (i.e., Northeast, Midwest, South and West). About 2% of all players were born in a foreign country and are analyzed separately. In the study cohort, nearly half of all NFL players were born in southern states compared to about 37% of NBA players.

7. Body Mass Index (BMI)

Body sizes of NBA and NFL players tend to be extreme, but not in the same way. On average, NBA players will be taller. However, nearly 90% of NFL players have overweight or obese BMIs compared to only 13% of NBA players who are overweight. The BMIs used for this analyses are based on heights and weights reported in the last year of each players’ NBA/NFL career. In the literature, this is generally known as “playing-time BMI.”

8. Player Position

This analysis is conducted within NBA and within NFL players only. In general, player position and body size are related, and in the NFL, position and race are also correlated. Speed and non-speed positions are compared among NFL players. Non-speed players are offensive and defensive linemen. All other positions are considered speed positions with the exception of punters and kickers (who are excluded from this analysis).

9. NBA/NFL Playing Experience

This chapter addresses whether number of years played in professional basketball or football is related to mortality. This can be viewed as a type of dose-response analysis.

10. Multivariate Analyses of Independent Risk Factors for Mortality

The analyses in chapter 5 – 9 consider one risk factor at a time while controlling or stratifying by year of birth. Chapter 10 identifies independent risk factors for mortality by controlling for year of birth plus all other significant risk factors uncovered in the previous chapters.

11. Comparisons between Former NBA and NFL Players and the US General Population

All of the analyses above compare mortality and its risk factors between NBA and NFL players. In this chapter, players in the two leagues are compared separately with the general population. Standardized mortality ratios are used to determine whether NBA and/or NFL players live longer than males in the general population taking into account year of birth and race.

12. Conclusions and Implications

This chapter includes a summary of the key findings and their implications. Limitations of the current study are provided. Public health implications including any preventative recommendations are the focus.

O autorze

Jeffrey S. Markowitz, DrPH, is an epidemiologist who has authored two books, Pigskin Crossroads: The Epidemiology of Concussions in the National Football League (NFL), 2010-2012 (2013), and Lost Seasons: Arrests, Suspensions, Career Chaos, and Mortality Among National Football League (NFL) Players (2016). From 1983 to 1992, Dr. Markowitz was an adjunct assistant professor of Public Health at the School of Public Health at Columbia University in New York, NY, USA.