This is the third Invited Commentary recognizing the contributions of the Journal of Cardiopulmonary Rehabilitation and Prevention (JCRP) over the past 40 yr. The first 2 provided overviews of the contributions related to cardiac rehabilitation and pulmonary rehabilitation.1,2 This Commentary, which is divided into 2 parts, provides a summary of the importance of the third major area of focus of JCRP, namely prevention. Part 1, provided here, focuses primarily on the lifestyle behaviors of dietary patterns and physical activity.
CVD RISK FACTORS
The prevalence of atherosclerotic cardiovascular diseases (CVDs) increased steadily during the 20th century, with mortality rates peaking in the 1970s. Over the past 40 yr, deaths attributed to CVD have plateaued or declined slightly; however, CVD remains the leading cause of death for adults in the United States. This trend persists for both men and women across multiple ethnicities including non-Hispanic white, black, Hispanic, Asian, and American Indian. Currently almost half of American adults, more than 121 million individuals, have some form of CVD (including hypertension), which carries an enormous economic burden that is projected to exceed $1 trillion in 2035.3 Despite these alarming numbers, current trends project cardiovascular (CV) health and CVD death rates to modestly improve over the next decade due to anticipated declines in smoking prevalence, dyslipidemia, and hypertension. However, there is concern that rising obesity rates, poor dietary patterns, and inadequate physical activity (PA) levels may offset these favorable trends.4
The incidence of atherosclerotic CVD is largely explained by a number of modifiable risk factors, including abnormal lipid levels (ie, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides), elevated systolic and/or diastolic blood pressure, diabetes mellitus, smoking, unhealthy diet, excessive alcohol intake, abdominal obesity, psychosocial stress, and physical inactivity.5 These 9 modifiable risk factors increase the risk of future CVD events and contribute to an estimated 90% of the population attributable risk of ischemic heart disease and stroke worldwide.6 Growing evidence suggests that adding cardiorespiratory fitness (CRF) to traditional risk factors significantly improves the classification of risk for adverse outcomes.7 Accordingly, prevention, treatment, and control of risk factors before clinical manifestation are common targets for interventions designed to reduce the burden of CVD.
Lifestyle behaviors are an essential component in preventing CVD, which includes cigarette smoking, dietary choices, and PA habits. Smoking cessation will be covered in part 2 of this commentary.
Dietary factors contribute to ∼45% of cardiometabolic-related deaths in the United States.8 Trends in dietary quality and energy intake, as assessed by the Healthy Eating Index, have generally improved for adults, youth, and children living in the United States since 1999, as substantiated by a reduced intake of trans fats and sugar-sweetened beverages along with an increased intake of whole fruits, whole grains, nuts and legumes.9,10 Caloric intake has remained consistent over the past decade after reaching highs in the early 2000s.8 Nevertheless, the prevalence of obesity continues to rise in US adults.3 More alarming is that while rates of obesity among US youth have remained unchanged over the past decade, the prevalence of severe obesity has increased.11 Because obesity and excess adiposity are major risk factors for CVD, these trends suggest that targeting obesity should continue to be a major cornerstone of CVD prevention.
Physical inactivity is the other lifestyle behavior that is a major risk factor for CVD. Although fewer than 25% of US adults meet the federal Physical Activity Guidelines for both aerobic and muscle-strengthening PA, the prevalence of physical inactivity has gradually declined in adults over the past decade while remaining relatively unchanged in high school students.12 Importantly, at any age, males are more likely to be physically active than females, which is most pronounced among high school students where boys are almost 3 times more likely to meet the Physical Activity Guidelines than girls. Thus, increasing rates of PA in adolescents, and in particular girls, could have a profound impact on CVD rates in the future. CRF, the outcome measure of PA, is a strong independent risk factor for CVD,13 and may also be trending downward,14 which is likely attributed to technologic advances and our increasingly hypokinetic lifestyle. Thus, it is apparent that some lifestyle factors are trending positively, such as reduced cigarette smoking and improved diet quality, that should contribute to lower rates of CVD. However, high rates of obesity and physical inactivity may remain barriers to preventative efforts to substantially reduce the prevalence of CVD.
STRUCTURED EXERCISE/PHYSICAL ACTIVITY
The importance of lifestyle for good health and prevention of chronic disease is hardly new, as espoused by Hippocrates almost 2500 yr ago: “If we could give every individual the right amount of nourishment and exercise, not too little and not too much, we would have found the safest way to health.” Information on heart-healthy dietary practices is summarized below. This section provides a brief summary of our understanding of the cardioprotective role of regular PA/structured exercise (ie, how much exercise is enough?) over the 40 yr since the inception of JCRP. The cardioprotective mechanisms associated with moderate-to-vigorous intensity exercise training were recently summarized (Figure).15
In 1978, the American College of Sports Medicine (ACSM) published their first Position Statement on the Recommended Quantity and Quality of Exercise.16 This statement provided recommendations for the basic components of a FIT exercise prescription, that is, a Frequency of 3 to 5 d/wk, an Intensity of 60-90% heart rate reserve, or 50-85% maximal oxygen uptake, and a Time of 15-60 min. The concept of total exercise work (volume or energy expenditure) was introduced as an important factor that drives the response in enhancing CRF. Updates to this statement were made in 1990 and 1998 as the evidence base was growing; however, the FIT recommendations remained largely unchanged.17,18 This growing body of evidence for the CV benefits of exercise training led the American Heart Association to include physical inactivity as the fourth major risk factor for CVD in 1992.19
Recognition of the cardioprotective role of exercise moved into the public health arena with the release of the landmark recommendations published in JAMA in 1995,20 which was followed by the first report of the US Surgeon General in 1996.21 These 2 publications broadened the perspective to include health benefits associated with regular PA as opposed to structured exercise training. Simultaneously, the focus of the recommendations shifted to emphasize accumulating 30 min/d of moderate-intensity PA on most d/wk. These reports were followed by the first PA Guidelines for Americans in 2008.22 These guidelines emphasized the need to accumulate PA, in ≥10 min/bouts, 150 min/wk of moderate-intensity or 75 min/wk of vigorous-intensity to achieve “substantial” health benefits, with “additional” benefits derived by increasing the weekly duration (up to 300 or 150 min/wk for moderate- or vigorous-intensity exercise, respectively). An update in 201823 largely maintained these recommendations, with the exclusion of accumulating ≥10 min/bouts, emphasizing total exercise volume as the important driver of health benefits.
Over the past decade, numerous research studies examining the components of exercise volume have identified exercise intensity as the likely major driver for cardioprotective benefits, including improved CRF.24–26 Interestingly, in the original ACSM position statement, it was noted that high-intensity training for only 10-15 min elicited significant physiologic and clinical benefits. One method that has been developed to capture the unique importance of intensity for deriving health-related CV benefits from exercise training is the Personalized Activity Intelligence (PAI).27 The PAI method requires heart rate monitoring and creates a PAI score that reflects the most recent 7 d, giving higher values to activities that are performed at higher intensities (higher heart rate).
In summary, regular exercise training is a major contributor to health and, as such, should be emphasized in both primary and secondary prevention programs. So, how much exercise is enough? Performing a sufficient amount of regular PA, that is, 150 min/wk of moderate-intensity exercise, can provide substantial health benefits. However, it has also become increasingly apparent that extending the duration of moderate-intensity PA (to 300 min/wk) results in additional benefits.28 Finally, emerging research strongly suggests that the gradual progression of exercise intensities, from moderate-to-vigorous to high-intensity training regimens (appropriate for most individuals), may result in even greater benefits.24,29–32
ECONOMIC VALUE OF PREVENTION: DO PHYSICAL ACTIVITY AND FITNESS PAY?
In the current era of rising health care costs, many health care systems have directed a greater emphasis toward promoting health behaviors that reduce the incidence of disability and chronic disease.33,34 Despite the widely-reported observation that more physically active individuals have fewer health problems and lower overall health costs, surveys show that most Americans do not meet the minimal recommendations for PA.35 Nevertheless, recent studies suggest that modulating CRF, PA patterns, or both, has a significant effect on health care utilization.36–41 These studies suggest that the higher health care costs among habitually sedentary, unfit individuals are likely attributed to factors that include greater illness, hospitalization, and disability.37–44
PHYSICAL INACTIVITY AND HEALTH CARE COSTS
Physical inactivity, usually defined as not meeting contemporary guidelines on PA, is associated with 10-30% of total health care expenditures for a given health care system or health insurance plan.37,45,46 Stated differently, simply getting the majority of subscribers in a given health plan to engage in ∼150 min/wk of moderate-intensity PA may have a considerable impact on reducing health care costs. Accordingly, estimates from the Centers for Disease Control and Prevention suggest that ∼$90 billion (USD) annually is attributed to inadequate levels of PA.37 Although cause-and-effect is difficult to establish in these studies, it is reasonable to assume that physical inactivity-related (and costly) medical conditions were more likely to occur among habitually sedentary individuals. With the escalating interest in cost-effectiveness in medicine, there has been an increasing number of related systematic reviews and meta-analyses,37,42–45 all of which suggest that PA interventions are reasonably cost-effective in varied groups with chronic disease. However, most acknowledge wide variation in the data and the need for additional randomized trials.
There are several notable caveats to these studies. Many have focused on relatively short-term (eg, <1-yr) employer-sponsored health promotion programs, raising the potential for participation bias (eg, those who choose to participate are healthier than those who do not). Because they are more readily available, existing studies have focused primarily on health care expenditures rather than cost-effectiveness per se. Costs have often been linked to Medicare claims data, largely limiting study populations to comparatively older subjects. Moreover, Medicare costs can differ significantly from private health care costs. PA interventions have also differed in the type, volume, and duration of exercise performed, even within disease categories. In addition, many of the estimates of population-level cost savings associated with higher PA patterns are based on hypothetical models that employed specific assumptions for values on costs of services. Finally, there are different types of costs (inpatient, outpatient, pharmaceutical, physician, or other services) and varied time frames during which they were measured (eg, 1-yr vs lifetime). Despite these limitations, an escalating number of studies have been largely consistent in demonstrating that health care expenditures are considerably lower among more physically active individuals.
CRF AND HEALTH CARE COSTS
CRF is recognized as a powerful risk factor for mortality, CV, and other adverse health outcomes.7,36 Despite the current increase in the prevalence of chronic illnesses and heightened interest in limiting the inexorable rise in health care costs, surprisingly few studies have evaluated the impact of CRF on health care costs. This is likely due to the escalating health care costs, the difficulty obtaining costs in a consistent manner,42,43 and the fact that CRF has generally been underappreciated as a risk factor.7 Some of the key studies relating CRF to health care costs are presented in the Table.40,41,47–50
Summary of Studies Assessing the Association Between Health Care Costs and Cardiorespiratory Fitness
||Type of Subjects
||Type of Costs
|de Souza de Silva et al41
||Referred male Veterans assessed over 7-yr period
||Total costs (inpatient, outpatient)
||Each 1-MET higher CRF associated with annual cost savings per person (USD) of $1346, $1823, and $2745 for normal-weight, overweight, and obese subjects, respectively
|Myers et al40
||Subjects undergoing maximal exercise testing for clinical reasons
||Total and annualized health care costs
||Each 1-MET higher CRF associated with $1592 (USD) annual reduction in health care costs/person (5.6% lower cost per MET)
|Bachmann et al48
||Healthy individuals in the Cooper Center Longitudinal Study undergoing CRF assessment
||Average annual health care costs obtained from Medicare
||Each 1-MET higher CRF associated with 6.8% and 6.7% reduced annual health care costs over a mean follow-up of 22 yr among men and women, respectively
|Weiss et al47
||Veterans Affairs patients referred for clinical exercise testing
||Inpatient and outpatient costs expressed in relative cost units
||Costs were incrementally lower by an average of 5.4% per higher MET
|Mitchell et al49
||Healthy male subjects undergoing medical examinations on 2 occasions (including maximal exercise testing)
||Incidence of medical treatments during a 1-yr period before each of 2 examinations
||Subjects with high CRF had fewer hospital visits and overnight hospital stays vs subjects with low CRF; men with low CRF at baseline who became fit during follow-up had reduced hospital stays
|Pronk et al50
||Employees enrolled in a worksite health promotion program
||Annualized health care costs incurred over a period of 33 mo
||Subjects with low CRF had 10% higher health care costs vs subjects with high CRF
Abbreviations: CRF, cardiorespiratory fitness; MET, metabolic equivalent; USD, US dollars.
Collectively, these findings suggest that the level of CRF, when objectively determined during maximal exercise testing,51,52 is inversely related to overall health care costs. Total health care costs are consistently lower per metabolic equivalent (MET; 1 MET = 3.5-mL O2/kg/min) achieved (in the range of 5-7%); this translates to ∼$1300 to S1800 (USD) annual cost savings/person/MET increment in CRF. Extrapolated to a broader health care system, the associated cost savings of even small improvements in CRF are enormous. These findings are consistent when adjusted for potential confounders, and, in at least one study, were not altered appreciably after excluding patients without CVD or those who died within 1 yr of follow-up.40 Cost savings with higher CRF appear to be more pronounced among overweight and obese subjects,40,41 although this requires confirmation from prospective cohort studies. CRF appears to be a powerful predictor of health care costs (surpassed only by heart failure).40,47 The latter finding is noteworthy, given the spectrum of risk factors and chronic conditions that are associated with rising health care costs, and the fact that CRF has traditionally not been considered a risk factor or included as a potential modulator among broader studies assessing health care costs.
HEART-HEALTHY DIETARY PRACTICES
Nutrition and proper dietary patterns are a cornerstone of healthy lifestyle behaviors for the prevention of CVD. According to a recent analysis, the #1 cause of death in the United States is the standard American diet.53 Although it is difficult to identify a universal cardioprotective or heart-healthy diet, there are several dietary patterns that are associated with reduced risk of CVD and related risk factors. Consumption of fruits, vegetables, whole grains, fish, nuts, legumes, low- or no-fat dairy products, and selected vegetable oils (eg, flaxseed, canola, and soybean) has been linked with CV health, while saturated and trans fats, processed and unprocessed red meat,54 sodium, added sugar, sugar-sweetened beverages, and refined carbohydrates are associated with higher CVD risk.55–57 For those who consume alcohol, it should be in moderation (≤2 drinks/d for men, 1 drink/d for women), ideally with meals. There is contradictory evidence regarding the impact of egg consumption on CVD. Although most studies suggest that a modest egg intake (≤1 egg/d) has no relation to blood lipids, mortality, or acute CV events,58–60 a particularly well-designed recent investigation found that higher consumption of dietary cholesterol or eggs was significantly associated with higher risk of incident CVD and all-cause mortality, in a dose-response manner.61
In a 2010 global modeling study, nearly 1.7 million deaths, about 1 in 10 from CV causes, were attributed to sodium consumption >2.0 g/d.62 The large, federally-funded Dietary Approaches to Stop Hypertension trial proved that the most effective dietary approach for lowering blood pressure was to limit sodium to 1500 mg/d by following a diet largely consisting of fruits, vegetables, whole grains, and nonfat dairy products.63 Today, the Institute of Medicine, the Centers for Disease Control and Prevention, and the American Heart Association64—all recommend ≤1500 mg of sodium/d, far below the standard American diet, which includes >3400 mg/d. Collectively, these findings highlight the substantial global burden of high-sodium intake and suggest that population-based initiatives to reduce the sodium content in our food products will unquestionably save lives.65 A practical rule-of-thumb method to facilitate smarter food selections relative to sodium content is:
The “1mg-of-sodium-per calorie” rule: Limit the sodium in mg to no more than the number of calories in each serving. Your daily goal: <1500 mg of sodium.
There is evidence that the Dietary Approaches to Stop Hypertension, mediterranean, vegetarian, and Japanese diets are associated with positive CV health outcomes.66–69 More recently, findings from the Prospective Urban Rural Epidemiology have challenged the notion that diets high in fats or carbohydrates are associated with CVD risk, highlighting the complex interplay between type of dietary fats (ie, saturated vs unsaturated) and dietary carbohydrates (ie, refined vs whole grain), as these relate to CV health.70 Regardless of macronutrient intake, achieving the appropriate energy intake to balance energy expenditure is essential for preventing weight gain and the elevated metabolic and CVD risks associated with obesity. Accordingly, certain dietary patterns should be considered in concert with other lifestyle behaviors such as regular PA and not smoking for optimal CV health.
COUNSELING PATIENTS TO FAVORABLY MODIFY UNHEALTHY LIFESTYLE HABITS
How do we engage our patients to actively make and embrace long-term lifestyle changes? The likelihood that patients will or will not engage in a particular lifestyle behavior is governed by a myriad of socioeconomic, attitudinal, and cultural factors, including their expectations of the effects, costs, and benefits of that behavior in relation to their health goals and the sacrifices (real or perceived) that will be required.71 This topic was reviewed in another commentary in this issue of the JCRP.72 It is important to help individuals identify and eliminate, or at least address barriers to change, to achieve successful behavior modification. Also, underlying psychosocial factors such as clinical depression, anger, apathy, chronic life stress, and personality traits must be addressed.
Commonly employed cognitive-behavioral strategies to facilitate behavior change include goal setting, self-monitoring, scheduled follow-up patient contact sessions, feedback and reinforcement, self-efficacy enhancement, incentives, modeling (eg, having the patient observe a counterpart who has already successfully engaged in behaviors that are compatible with his/her goals), problem-solving, and relapse prevention strategies.73,74 The Stages of Change Model should also be used to tailor messages on lifestyle counseling to patient “readiness to change” to increase program effectiveness. Finally, motivational interviewing should also be utilized by health care providers during patient encounters to help facilitate a behavioral transformation.75,76
For many patients, setting initial goals and taking action for lifestyle modification and CV risk reduction may be unrealistic and overwhelming, especially if contemporary guidelines and recommendations are embraced. Although inertia is a major barrier to making permanent lifestyle changes, it is also one of the easiest obstacles to overcome. We simply need to get patients to act. Any action they take, no matter how trivial, may help to gain momentum. Our approach would be to overcome inertia with immediate, downscaled goals,71 for example, relative to dietary modification, initially replacing 2 unhealthy foods or snacks each day with fruits or vegetables (eg, eating a salad instead of pizza for lunch or selecting an apple instead of potato chips). This approach gets patients moving in the right direction, many of whom may subsequently find themselves not only meeting but exceeding these goals. In summary, the issue is not information, but methods, motivation, and accessibility in achieving lasting behavior changes.
Risk-factor reduction can substantially reduce the risk for CV events. It should start with and always include promoting lifestyle modification (eg, regular PA and cardioprotective dietary practices). These preventive lifestyle habits are both associated with improved CV outcomes and impressive mortality reductions. When combined, even greater survival benefits are likely to be achieved. Additionally, exercise preconditioning has been shown to attenuate the adverse manifestations and myocardial injury associated with acute CV events in humans.77
As CV health care providers, we need to become champions for individuals to achieve healthy lifestyle overhauls to prevent the development and progression of CVD. Achieving these goals will, no doubt, involve embracing research-based counseling strategies, behavior change interventions, and expanded health care system CV prevention/treatment options. The value of the JCRP in promoting these objectives over the past 40 yr is apparent.
The authors thank Brenda White for her meticulous preparation of this article and for carefully checking the accuracy of our references throughout the text and in the citations listed at the conclusion of this commentary.
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