Cardiovascular Risk and Disease Among Masters Endurance Athletes: Insights from the Boston MASTER (Masters Athletes Survey To Evaluate Risk) Initiative

While habitual exercise reduces the risk of cardiovascular (CV) disease, it does not confer complete immunity [1, 2]. Masters athletes (MAs), men and women over the age of 35 who participate in organized competitive sport, are a rapidly growing segment of the population that are increasingly common in clinical practice [3]. Atherosclerotic coronary artery disease (CAD) is the most common cause of sudden death among MAs [4], and recent data suggest that MAs may be at higher risk for CAD than their otherwise similar sedentary counterparts [5, 6]. In addition, emerging data demonstrate associations between other forms of CV disease including atrial fibrillation (AF) and nonischemic myocardial fibrosis and exercise exposure in excess of low to moderate levels [7, 8]. However, lifestyle characteristics, CV risk factors, and their relationships with established CV disease among MAs remain incompletely understood.

To address this knowledge gap, we undertook the present study. Specifically, we utilized an Internet-based survey tool to collect demographic, lifestyle, and medical information from an unselected, community-based population of MAs. The primary goal of this initiative was to develop a comprehensive clinical profile of the contemporary MA with an emphasis on the relationship between CV risk factors and established disease.

The Boston MASTER study was conducted to develop a comprehensive CV profile of the contemporary MA. Key findings from this study, a characterization of men and women with more than 20 years of competitive endurance sport exposure who at the time of this study were completing approximately four times the amount of physical exercise recommended for health optimization [11], can be summarized as follows. First, 64 % of this population had at least one established CV risk factor with a family history of premature atherosclerotic disease and prior tobacco exposure identified as the most common issues. Second, there was a 9 % prevalence of established CV disease that was accounted for almost exclusively by AF and CAD. Third, roughly one in seven MAs reported overall dissatisfaction with the healthcare system due in part to care providers’ tendency to dismiss complaints due to their status as athletes. Finally, our data shed important insights into CV disease characteristics among MAs. Specifically, prevalence of AF appears to be associated with years of cumulative exercise exposure and concomitant hypertension, while in contrast, CAD appears to be associated with traditional atherosclerotic risk factors (i.e., hypertension, dyslipidemia) and negligibly associated with any element of prior exercise exposure.

Routine low to moderate intensity physical exercise leads to favorable changes in CV risk factors [12–14] and is recommended for both the primary and secondary prevention of CV disease [11]. However, the dose response relationship between exercise and CV outcomes remains incompletely understood, and there is mounting evidence that people who engage in high levels of exercise may be surprisingly susceptible to specific forms of heart disease including AF [7], coronary atherosclerosis [6], and myocardial fibrosis [15]. In addition, two recent observational population-based studies suggest that the mortality benefits afforded by physical activity may dissipate among people who engage in the highest levels of exercise [16, 17]. Definitive explanations for these intriguing observations remain speculative, in part because studies aimed at examining the people who engage in the highest levels of exercise have been lacking. Findings from this study present a comprehensive social and CV medical profile for this segment of the population and shed novel insights into why high-level exercisers may be susceptible to common forms of heart disease.

Our data support the notion that AF is the most common acquired CV condition among MAs and complement recent work demonstrating an association between duration of participation in competitive athletic and susceptibility to arrhythmia [7, 18]. In addition, we now demonstrate that concomitant hypertension is independently associated with prevalent AF. Future prospective interventional studies will be required to determine whether aggressive blood pressure control will lead to a reduced burden of AF among chronic high-level exercisers. Unlike AF, we detected no associations between atherosclerotic CAD and exercise exposure. This finding was somewhat surprising following recent reports of increased CAD among seasoned marathon runners [5, 6]. While we cannot exclude the possibility that high-level exercise plays a role in the progression of atherosclerosis, our data suggest that the presence and perhaps undertreatment of traditional atherosclerotic risk factors are a far more powerful determinant of CAD risk. This finding helps to explain why CAD occurs among seasoned exercisers and simultaneously provides opportunities to improve primary prevention efforts in clinical practice including the targeted treatment of modifiable atherosclerotic risk factors.

Existing data examining CV risk factor prevalence among competitive MAs are sparse. De Matos et al. reported age-dependent increases in the rates of abnormal lipid profiles, body mass index, and fasting glucose among 247 Brazilian MAs [19]. Risk factor prevalence data from the present study builds on this prior work in several important ways. The nontrivial rates of hypertension (12.4 %), dyslipidemia (7.4 %), and obesity (2.9 %) observed among this current cohort of MAs are substantially lower than those recently reported in the general population [20]. Thus, long-term dedication to high levels of exercise may substantially reduce the burden of these disease determinants but does not appear to eliminate them completely. In contrast, the rate of tobacco exposure observed in our cohort of MAs is similar to that reported in the general population. Our finding that prior tobacco exposure was an independent risk factor for CAD indicates that it is a significant source of morbidity among MAs. While speculative, it is likely that some older athletes adopt a high-level exercise lifestyle following years of previous risk exposure in an attempt to offset previous high-risk lifestyle choices. Clinical characterization of overall risk and future studies geared toward delineating disease pathogenesis in this population should take measures to address this issue.

To our knowledge, healthcare utilization and satisfaction have not been previously characterized among MAs. It is noteworthy that approximately one in four of our study participants did not receive routine primary care. This finding, coupled with the observed prevalence of both risk factors and disease, suggests a need for more effective public health outreach campaigns that should be designed to complement current screening recommendations for this specific population [3, 21]. Among those athletes who were engaged in the healthcare system, one third had received care from a CV specialist and 63 % had been subjected to one or more forms of CV diagnostic testing. These findings highlight the need for CV clinicians to be familiar with the unique characteristics of this population and emphasize the importance of developing MA-specific algorithms for the implementation and interpretation of CV testing. Optimal care of aging athletes may best be accomplished through a partnership between sports medicine physicians and CV specialists with expertise in the care of athletes. Finally, we observed a rate of overall healthcare dissatisfaction of 14 % with several underlying explanations that are unique to this population. Specifically, participants reported dissatisfaction due to (1) having their concerns dismissed due to their status as ostensibly healthy athletes and (2) inadequate knowledge among care providers about issues specific to athletes. These reasons for dissatisfaction indicate a previously unrecognized form of patient-provider mismatch that may be addressed by refinements in clinical training and further development of sports cardiology as an established area of expertise.

We acknowledge several limitations of this study. Data acquisition was performed using an Internet-based survey, and therefore, several potential sources of error must be addressed [22]. We sought to minimize the impact of nonresponse error by excluding all data derived from surveys that were less than 95 % complete. Similarly, we sought to minimize the likelihood of inaccurate response data by utilizing concise and clearly worded survey questions coupled with very specific trait definitions of cardiac risk factors and disease to reduce the impact of measurement error. As we studied MAs from a relatively confined geographic area, we acknowledge the possibility of coverage error that may limit the generalizability of our results to MAs in other locations. Similarly, we are unable to exclude some element of sampling error as our data reflect voluntary survey participation and it is possible that respondents on either end of the health spectrum were more or less likely to participate. However, we attempted to reduce sampling bias by advertising this survey as a general exercise and lifestyle study, thereby minimizing selection as a function of health status, and made our survey available to a large unselected group of potential participants. Finally, given the observational and cross-sectional nature of our data and the relatively low incidence of established disease, we are unable to determine the clinical significance and modifiability of the reported ORs.

People including MAs who engage in high levels of routine physical exercise are not completely protected from CV disease. AF and CAD have emerged as important sources of morbidity and mortality in this segment of the population and appear to be associated with distinctly different determinants of disease pathogenesis. Widespread recognition of disease-specific risk profiles coupled with targeted therapeutic efforts among MAs may hold value for preventing the development of CV disease in this population.