Review of Cardiometabolic Risk Factors Among ...

clinical focus: neurology/stroke, rehabilitation medicine, cardiometabolic Health

Review of Cardiometabolic Risk Factors Among Current Professional Football and Professional Baseball Players John H. Helzberg, MD; Joel Camilo, MD; Joseph F. Waeckerle, MD; James H. O’Keefe, MD

Abstract: Data on the development of cardiovascular disease in professional football players are conflicting. Studies have documented a higher prevalence of obesity, lower high-density lipoprotein cholesterol levels, increased left ventricular and left atrial size, and higher prevalence of metabolic syndrome in former professional football linemen compared with nonlinemen. It has been suggested that former National Football League players are at risk for early cardiovascular disease and premature death. A print media report in 2006 indicated an increased prevalence of cardiovascular disease and early mortality in professional football players compared with professional baseball players. However, there has been little scientific evaluation of cardiovascular risk factors in professional baseball players. Our data suggest that there is increased cardiovascular disease risk in football players, but this is limited to heavier linemen. In preliminary studies, baseball players do not appear to demonstrate the same increased risk. However, caution should be used in the interpretation of increased cardiovascular disease risk, as it does not necessarily translate into early increased mortality. Keywords: cardiovascular disease; cardiometabolic syndrome; risk factors; football; baseball John H. Helzberg, MD 1 Joel Camilo, MD 1 Joseph F. Waeckerle, MD 1 James H. O’Keefe, MD 1 Saint Luke’s Hospital of Kansas City, University of Missouri-Kansas City School of Medicine, Kansas City, MO 1

Correspondence: James H. O’Keefe, MD, University of Missouri-Kansas City School of Medicine, 4330 Wornall Road, Suite 2000, Kansas City, MO 64111. Tel: 816-751-8480 Fax: 816-756-3645 E-mail: [email protected]

Introduction In 1992, at the request of the National Football League (NFL) Players Association, the National Institute of Occupational Safety and Health (NIOSH) conducted a study of 6848 retired professional football players to investigate the possibility that retired players were dying prematurely.1 Overall, professional football players had a 46% lower mortality rate than an age-, gender-, and race-matched population. When the cohort was stratified by position, linemen had a 52% higher risk of cardiovascular disease (CVD) mortality compared with the general population, and also had a 3.7-fold greater risk of death from heart disease compared with other position players. The NIOSH concluded that greater body mass index (BMI) associated with the linemen position contributed to this higher CVD mortality.1 Obesity has been demonstrated to increase risk for CVD disease and death in the general population.2–4 In a study of one NFL team, linemen had the highest prevalence of obesity, as well as the highest levels of total cholesterol, low-density lipoprotein cholesterol (LDL-C), and triglyceride levels, and the lowest high-density lipoprotein cholesterol (HDL-C) levels of all position groups.5 Hargrove6 compared mortality rates for 3850 professional football players with 2403 professional baseball players who had died in the past 100 years.6 The author reported that football players whose BMI indicated they were obese were twice as likely to die before the age of 50 years than baseball players. He also noted that 22% of deaths among NFL players were from CVD. Offensive and defensive linemen had a 52% greater risk of dying of heart disease than the general population. Although the report was not scientifically valid, the topic was provocative. Hargrove6 highlighted legitimate concerns regarding the current and retired NFL players’ physical stature and quality of life. Because of the popularity of the sport, the topic garnered much media discussion. More importantly, these observations instigated further scientific investigations on the health of professional football players. The large size of players as well as sporadic deaths of active and young retired professional football players have raised questions regarding an associated increase in CVD risk.7,8 Waist-to-height ratio of players from one NFL team is shown in Figure 1.9 More than 50% of NFL players meet BMI criteria for being overweight or obese.10 It is well established that obesity, as classified by BMI criteria, increases the risk for CVD and death from all causes.2,11 However, in large muscular athletes, population BMI cutoffs may overestimate body fat.12

© THE PHYSICIAN AND SPORTSMEDICINE • ISSN – 0091-3847, October 2010, No. 3, Volume 38

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Helzberg et al Figure 1. Waist-to-height ratio by position in professional football players.

Studies have suggested that fitness may provide protection against the health risks of obesity,13 although other investigations have found that physical activity is beneficial but does not eliminate these risks.14 Of great concern is the growing size of high school athletes, with 45% to 60% of linemen (generally the largest players) being overweight or obese.15 Football linemen of all ages are often more obese than their peers who play other positions. Obesity and overweight status are more prevalent among young (8–15 years) linemen when compared with other position players.16 Collegiate linemen are also increasing in size. In a large study of collegiate athletes that evaluated player size, football linemen were found to have the greatest increase in weight and BMI.17 Size-related cardiovascular health risks may develop prematurely in young linemen, particularly if their exercise levels diminish and their high calorie intake persists.

Cardiometabolic Syndrome Parameters in Football Players Cardiometabolic syndrome and insulin resistance are 2 common conditions associated with long-term morbidity,

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such as premature coronary heart disease and type 2 diabetes.18,19 The National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) has established criteria based on levels of triglycerides, HDL-C, abdominal obesity, glucose, and blood pressure to define cardiometabolic syndrome in both adolescents and adults. Any subject meeting 3 of these 5 criteria is classified as having cardiometabolic syndrome. It has been suggested that cardiometabolic syndrome may be a more important risk factor than tobacco use in the future development of coronary artery disease (CAD).20 Furthermore, cardiometabolic syndrome is associated with insulin resistance, an important factor in potentiating the risk of premature CAD and type 2 diabetes.21 In a cross-sectional study of 90 division 1 collegiate football players, Borchers et al22 recently estimated the prevalence of cardiometabolic syndrome, insulin resistance, and associated risk factors, and found a strong association between obesity and both cardiometabolic syndrome and insulin resistance in these players. They found that the prevalence of obesity, insulin resistance, and cardiometabolic syndrome was 21%, 21%, and 9%, respectively. In their analysis, obesity was closely



Cardiometabolic Risk Factors in Professional Football and Baseball Players

associated with cardiometabolic syndrome (P , 0.0001) and insulin resistance (P , 0.0001). All subjects with cardiometabolic syndrome were obese, and the odds for insulin resistance in the obese group were 10.6 times greater than in the nonobese group. Of the players who were linemen (n = 29), 19 (100%) of 19 were obese, 13 (68%) of 19 had insulin resistance, and all had cardiometabolic syndrome. They found that compared with other positions, linemen were at significant risk for cardiometabolic syndrome and insulin resistance. Miller et al23 previously reported a BMI of $ 30 kg/m2, an HDL-C of # 40 mg/dL, a fasting glucose of $ 100 mg/dL, and the cardiometabolic syndrome to be more prevalent in retired NFL linemen compared with nonlinemen. In contrast with the Borchers study, Chang et al24 found that despite their large body size, retired NFL players do not have a greater prevalence of cardiovascular risk factors or amount of coronary artery calcium than community controls. In their study, cardiovascular risk factors and coronary atherosclerosis in 201 retired NFL players were compared with 2 groups of community controls (the population-based Dallas Heart Study and the preventive medicine cohort from Aerobics Center Longitudinal Study). Coronary atherosclerosis was measured by computed tomography as coronary artery calcium. Compared with population-based controls, retired NFL players had a significantly lower prevalence of diabetes, hypertension, sedentary lifestyle, and cardiometabolic syndrome. However, there was no significant difference in the prevalence of detectable coronary artery calcium or distribution of coronary artery calcium when the retired NFL players were matched with sedentary or physically active control groups. Retired NFL players did not have significantly greater or lesser amounts of coronary atherosclerosis than expected for their age. In retired NFL players, age and hyperlipidemia (not body size) were the most significant predictors of coronary artery calcium. They did find a higher prevalence of impaired fasting glucose and hyperlipidemia in the retired NFL players, demonstrating the need for early cardiovascular risk factor screening and maintaining a physically active lifestyle. In the largest study to date of current NFL players, Tucker et al25 found a similar CVD profile to the general population in 504 physically active veteran professional players from a convenience sample of 12 NFL teams. Data were compared with men of the same age in the general US population from the Coronary Artery Risk Development In Young Adults (CARDIA) study, a population-based observational study of 1959 participants aged

23 to 35 years recruited between 1985 and 1986. Compared with a sample of healthy young adult males, taller and heavier active NFL players had a lower prevalence of impaired fasting glucose and a similar prevalence of dyslipidemia. Of concern was the fact that they found a higher prevalence of prehypertension and hypertension among NFL players. Moreover, hypertension and prehypertension were common. In a smaller cohort from one NFL team, our group9,26 has demonstrated an increased prevalence of hypertension and hyperglycemia in active NFL players compared with age- and sex-matched controls from the National Health and Nutrition Examination Survey (NHANES), as shown in Figure 2. Moreover, subset analysis demonstrated that obesity and cardiometabolic syndrome were found only in the linemen subset. Elevated alanine aminotransferase levels in players were statistically correlated to measures of obesity, hypertension, and a marker of insulin resistance, with triglycerides:HDL ratio of . 3.5 (Figure 3).

Increased Prevalence of Surrogates for CVD Croft et al27 speculated that although greater BMI levels contribute to the postulated higher rate of cardiovascular mortality in retired linemen, unmeasured cardiac risk factors may also contribute. Although increased left ventricular mass is a well-established cardiovascular risk factor in the general population28 and is prevalent in elite college players,29 retired professional football players had not undergone cardiac studies to assess cardiac morphology. With the premise that left atrial size is directly associated with the risk of cardiovascular-related death and is partially related to left ventricular mass,30 Croft et al27 examined echocardiographic characteristics of 487 retired NFL players and found a higher left ventricular mass and left atrial size in the retired linemen subset. Additionally, they found that BMI, linemen player position, and systolic blood pressure were significant independent predictors of left ventricular mass.

Conclusion of Data on Football Players The data concerning early CVD risk in professional football players are conflicting. Although the heavier linemen have risk factors for the development of cardiac disease, long-term follow-up studies are needed to fully address this. Interventions to treat existing risk factors will need to be consistently employed. These treatments place necessary limitations on the


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Helzberg et al Figure 2. Cardiometabolic parameters and markers of obesity and insulin resistance in professional football players compared with the general population.

Abbreviations: BP, blood pressure; FB, football; HDL, high-density lipoprotein; NHANES, National Health and Nutrition Examination Survey; Trigs, triglycerides. Figure 3. Association of elevated alanine aminotransferase (ALT) in professional football players with body mass index, cardiometabolic parameters, and markers of obesity and insulin resistance.

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conclusions of future studies. We believe that heavier players will be at risk for early CVD, particularly after their careers are over, and their risks increase with age and decreased physical activity. Thus, former players should receive behavioral, nutritional, and possibly pharmacologic therapy to address their risks. The same holds true for heavier athletes in other sports. It appears that exercise, though protective, does not eliminate the future cardiac risk of obese professional football players, particularly linemen. This is likely due in part to the cardiometabolic risk associated with obesity.

Cardiovascular and Metabolic Risk Factors in Professional Baseball Players The Scripps Howard News Service reported increased CVD and premature mortality in professional football players compared with professional baseball players. Surprisingly, there has been little scientific evaluation of CVD risk in professional baseball players. We recently reported that professional baseball players have a lower prevalence of waist circumference ($ 100 cm) and waist-to-height ratio (. 0.5) when compared with football linemen. There was no significant difference in obesity using the same waist-based parameters in baseball players and nonline-

men. As obesity is thought to increase CVD risk, the large size of linemen may explain this increased risk and the reported higher early mortality of professional football players (Figure 4). These parameters are displayed in Figure 4. In a comparison of 155 professional baseball players with 69 professional football players, a higher prevalence of hypertension was found in the baseball players compared with the football team as a whole as well as the nonlinemen subset. However, there was no significant difference in hypertension between baseball players and the linemen subgroup, with both groups demonstrating an increased prevalence of hypertension compared with the NHANES III cohort. This increased rate of hypertension among professional baseball players is somewhat unexpected and may relate to unmeasured variables, including ethnicity, genetics, supplements, chewing tobacco, and sympathomimetic medications.31 Professional baseball players demonstrated a lower prevalence of hyperglycemia (glucose $ 100 mg/dL) than football players as a whole. This observation is somewhat skewed by the fact that hyperglycemia was found commonly in linemen. The subset of nonlinemen football players appears to have some healthier attributes as compared with baseball players. They have

Figure 4. Cardiometabolic parameters and markers of obesity and insulin resistance in professional baseball players compared with the general population.

Abbreviations: BP, blood pressure; BB, baseball; HDL, high-density lipoprotein; NHANES, National Health and Nutrition Examination Survey; Trigs, triglycerides.


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Helzberg et al Figure 5. Comparison of cardiometabolic parameters and markers of obesity and insulin resistance in professional football players, professional baseball players, and the general population.

Abbreviations: BB, baseball; BP, blood pressure; FB, football; HDL, high-density lipoprotein; NHANES, National Health and Nutrition Examination Survey; Trigs, triglycerides.

a decreased incidence of hypertension (blood pressure $ 130/85 mm Hg) and ALT $ 40 IU/L. Cardiometabolic parameters and markers of obesity and insulin resistance in professional baseball and football players as well as the general population are shown in Figure 5.31 Various authors have studied the relationship of elevated ALT and cardiometabolic syndrome, diabetes, and CVD demonstrating that elevated ALT is a biomarker for the presence of these risk factors.10–13,32 There are obvious limitations to our studies. The methodology is limited because convenience samples from one professional football organization and one professional baseball organization were included. There are validity issues from possible confounding variables that the authors could not control. Moreover, our study (as well as most other reports to date) is limited by the inability to assess mortality as an endpoint. The optimal analysis of cardiovascular mortality would entail a long-term, prospective, observational study comparing baseball players with football players throughout their careers and during retirement. Although this type of study would be ideal, it would be logistically difficult and require long follow-up periods.

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Conclusion The long-term health risk of obesity in professional football players is unanswered. Earlier studies did not demonstrate increased mortality but may not be applicable to the heavier current players. Our data suggest early increased CVD risk factors in heavier football lineman. Longitudinal studies are required to further evaluate this risk. However, studies performed without intent to treat may not be entirely ethical. Our goal has been to identify players at risk with the intent of nutritional counseling and possibly pharmacologic intervention, particularly after their professional careers have ended, when their risk is likely to increase with age and reduced physical activity.

Acknowledgments The authors would like to thank Lori J. Wilson, Nick Swartz, and David Price for their contributions to this article.

Conflict of Interest Statement John H. Helzberg, MD, Joel Camilo, MD, Joseph F. Waeckerle, MD, and James H. O’Keefe, MD disclose no conflicts of interest.




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