Editor's Note: Commentary based on Kim JH, Hollowed C, Liu C, et al. Weight Gain, Hypertension, and the Emergence of a Maladaptive Cardiovascular Phenotype Among US Football Players. JAMA Cardiol 2019;Oct 16 [Epub ahead of print].

Study Questions:
What is the progression of independent risk factors associated with cardiovascular risk over serial years of play in collegiate football players?

Methods:
Freshman collegiate football players from two National Collegiate Athletic Association Division I programs were recruited between June 2014 and June 2017 and analyzed over 3 years of serial competitive football participation. Transthoracic echocardiography, clinical assessments, and vascular applanation tonometry were performed to assess factors associated with cardiovascular risk.

Results:
One hundred twenty-six freshman collegiate football players (62 white males, 63 black males; 49 linemen, 77 non-linemen) of a total of 186 recruited athletes were included in the analysis. Fifty-five athletes reached the final point of analysis, defined as the immediate onset of the junior year postseason. The average weight for all 126 athletes was 101.0 kg. Mean systolic blood pressure at baseline (onset of freshman season) was 129.1 mmHg. After adjusting for height, player position, and race, there were significant increases in weight (average increase 4.74 kg, p < 0.001), systolic blood pressure (average increase 11.6 mmHg, p < 0.001), and arterial stiffening (measured as pulse-wave velocity with average increase of 0.24 m/s, p = 0.007) and significant declines in E' (average change -1.7 cm/s, p < 0.001) over 3 years of serial football participation. Weight gain was significantly associated with arterial stiffening (p = 0.003) and the development of concentric left ventricular hypertrophy (p < 0.001). Increased systolic blood pressure was significantly associated with both arterial stiffening (p = 0.007) and the development of concentric left ventricular hypertrophy (p = 0.02). While linemen had higher systolic blood pressures, lower E', and higher pulse wave velocity, there was no statistically significant difference compared to non-linemen.

Conclusions:
Weight gain and increasing systolic blood pressure in collegiate football players are associated with increased risk for concentric left ventricular hypertrophy, arterial stiffening, and reduced left ventricular diastolic function, all factors that contribute to the development of a pathologic cardiovascular phenotype in young athletes.

Perspective:
Cardiovascular risk assessment in young competitive athletes is often incomplete or deferred until the onset of clinical symptoms or after a cardiac event. As a result, risk factors are not routinely monitored, and cardiovascular mortality rises over time. Mortality data for football players compared to alternative sports such as baseball is quite astounding and suggests that sport-specific lifestyle changes meant to enhance athletic performance (e.g. weight gain in linemen) may lead to a pathologic cardiovascular phenotype.¹

The traditional definition for "athlete's heart" proposes that left ventricular concentric remodeling is a physiologic response to strength training, though a recent longitudinal study revealed that left ventricular concentric remodeling was not seen in athletes who performed resistance exercise.^2,3 Kim et al.'s study suggests that the commonly accepted association between left ventricular concentric remodeling and resistance training may no longer be valid and in fact may be reflective of pathologic left ventricular changes. More specifically, weight gain during serial football participation may be a useful marker for early identification of subclinical cardiovascular pathology, quantified by easy-to-obtain metrics, which include blood pressure and echocardiographic assessment of left ventricular wall thickness/hypertrophy and tissue-doppler E' velocity. Reassuringly, risk stratification and close surveillance of weight changes and blood pressure are simple to integrate in the care of young, competitive athletes and should be assessed in a serial fashion to ensure that cardiovascular risk is appropriately addressed and managed.

A notable limitation of Kim et al.'s study is the lack of a control group to delineate whether weight gain, elevated blood pressures, and subsequent concentric left ventricular hypertrophy are sport-provoked phenomena or merely reflective of natural occurrences in healthy, non-athlete college students over 3 consecutive years. Additional limitations include incomplete follow-up at the onset of the junior year postseason, the lack of ability to assess the influence of detraining on measured outcomes, and inability to identify other mechanistic factors for subclinical cardiac pathology in athletes with increasing weight and blood pressure (i.e. obstructive sleep apnea). Despite these limitations, the study findings are quite promising in suggesting the importance of early integration of cardiac risk assessment in young, college athletes as a strategy to improve long-term cardiovascular outcomes.

Citations

1. Nguyen VT, Zafonte RD, Chen JT, et al. Mortality among professional american-style football players and professional american baseball players. JAMA Netw Open 2019;2:e194223.
2. Morganroth J, Maron BJ, Henry WL, Epstein SE. Comparative left ventricular dimensions in trained athletes. Ann Intern Med 1975;82:521-24.
3. Spence AL, Naylor LH, Carter HH, et al. A prospective randomised longitudinal MRI study of left ventricular adaptation to endurance and resistance exercise training in humans. J Physiol 2011;589:5443-52.

Keywords: Sports, Athletes, Football, Weight Gain, Blood Pressure, Hypertrophy, Left Ventricular, Resistance Training, Risk Factors, Pulse Wave Analysis, Longitudinal Studies, Cardiovascular Diseases, Control Groups, Follow-Up Studies, Blood Pressure Determination, Systole, Diastole, Echocardiography, Athletic Performance, Risk Assessment, Sleep Apnea, Obstructive, Life Style, Phenotype, Manometry, Hypertension

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