Cardiovascular Risk Management Must Always Consider Social Determinants of Health: Past Lessons, Data, Proposals and Challenges

Traditionally, management of cardiovascular risk (CVR) has been focused on clinical factors, and this approach has advanced cardiology and improved patient outcomes for decades. Nevertheless, CVR is influenced by biological, psychological, economic, and environmental elements, as well by health systems. The broader background concerning the social determinants of health (SDH) and socioeconomic status (SES), a major component of SDH, upon noncommunicable diseases and CVR in particular has recently been reviewed in detail elsewhere.

Unwitting experiments of nature and fortune, particularly the ravages of war and political changes, create circumstances that would otherwise be unethical to produce. Study of such unusual conditions is warranted, since they may inform concepts that have applications when order is restored and conditions are stable.
An outstanding example from Cuba concerns the relationship between SES and CVR. After a period of decline, the USSR dissolved in 1991; it was a major trading partner with Cuba and a prominent member of the Counsel of Mutual Economic Help (CAME, for its acronym in Spanish) of the socialist countries [1][2][3][4][5][6][7][8][9][10]. This sudden absence of support began a "Special Period" in Cuba, characterized by a severe shortage of oil, transportation, electricity, and food. The famine that followed involved a marked reduction in consumption of animal protein, a corresponding increase in plant food intake, and a rise in physical activity (walking, bicycling) in the general population. In a cohort that randomly measured CVR factors before (1988) and during (1994) the Cuban Special Period in the 1990s, there was a dramatic decrease in sedentary lifestyle, obesity, hypercholesterolemia, diabetes, and tobacco use (Table 1 and Figure 1) [5]. Attention is called to two features: (i) the fall in mean cholesterol levels was on the order of the therapeutic effect of statin drugs [11] and (ii) of all modifiable risk factors, blood pressure was the only one to rise during the same period [10]. In practice, this descriptive research was a quasiexperimental study of the health effects of the unexpected intervention of the severe socioeconomic crisis endured by the Cuban people. Extending the period of observation of the Cuban cardiovascular risk factor landscape from 1980-2010, other investigators confirmed the findings associated with Cuban economic deprivation in the mid-1990s [12]. Specifically, there was a fall in prevalence of both type 2 diabetes (DM) and coronary heart disease (CHD). In the rebound period, from 1994-2010, the prevalence of obesity and overweight rose 19.4 percentage points, followed by a 116% increase in DM prevalence and 140% increase in DM incidence. Six years into the rebound, in the period 2002 to 2010, DM mortality increased by 49% accompanied by a rise in CHD deaths [12,13]. The association between forced hypocaloric diets, transition to plant-based fare, weight loss, greater physical activity, lower CVR, and subsequent reversal was striking. Although unproved, one putative explanation for the rise in blood pressure was the unmeasured yet obvious rise in psychosocial stress during the Special Period.

Layered Deleterious Effects beyond Traditional Risk Factors
In considering the effects of catastrophic environmental, social and economic change, at one level the prevalence of major traditional risk factors and subsequent effects upon outcomes is of concern, as described above. There is a linear relationship between number and intensity of risk factors and subsequent cardiovascular (CV) outcomes [14,15]. Tracking of common risk factors from youth to adulthood, which receives greatest attention in health systems focused upon individual risk, is a well-documented phenomenon [16][17][18]. Importantly, tracking of risk factors and their precursors applies to later adverse changes in pathological findings, biomarkers, other evidence of subclinical disease, and overt clinical manifestations of CHD [19][20][21].
Ascending vertically with age, from children to young adults and older, there are innumerable negative exposures the population may endure which result in negative physical and mental effects over time. Such accumulated insults, unmeasured but assuredly present, track into adulthood to impair future health. Thus, in the example given above during the Special Period in Cuba, one would expect a spectrum of subclinical negative exposures linked to traditional risk factors which remain largely unrecognized.
Expanding horizontally to include the greater components of SDH, there are also cumulative micoinsults as granularity increases, with some consequences more direct than others. These may occur from economic instability (poverty, stress, unemployment, lack of opportunity, food insecurity, housting instability), within the social and community context (sanitation, discrimination, incarceration, civic participation, and lack of social cohesion and support), within the sphere of education (high school graduation, higher education, access to job training, early childhood development, access to mass media and educational opportunities), health and care (access, health literacy, medications, screening, testing, procedures), and neighborhood and built environment (access to foods supporting healthy eating patterns, quality of housing, public safety, environmental conditions, access to transportation) [22].
The evidence base also includes examinations of relationships of SES to CV outcomes or intermediaries. For instance, childhood SES may predict metabolic syndrome, impaired fasting glucose, and DM up to 31 years later in adulthood [23]. Socioeconomic mobility, thought to be dependent upon elasticity of income between parent and grown child, but perhaps better correlated with person-level rank association, does have a relationship with ensuing ideal CV health, but the life course of both is highly modifiable [24]. The implications of the latter data are uncertain, and may also be somewhat unique to the U.S., where income mobility is low, but certainly need consideration.
In the adult population, there is ample evidence that SDH and deficiencies in health systems are negatively associated with cardiovascular outcomes and mortality [25]. For example, in one large study 6 psychosocial and socioeconomic factors were linked with a higher risk of CV death: unemployment, depression, unmarried status, poor contact with friends or relatives, and lack of material and all independent of each other. The health gap resulting from inequality at multiple levels is immense [26,27]. Unfortunately, wealth-related national inequality renders secondary prevention with aspirin, β blockers, angiotensin-converting enzyme inhibitors, and statins unavailable or unaffordable in many global populations [22]. As a result, low SES in low-and middle-income countries create impediments in accessing essential life-giving resources, which threatens attainment of planned goals to control CV disease and NCD globally [28,29]. When WHO member states joined in 2011 to forge the 25 × 25 initiative with the goal of a 25% reduction in premature NCD mortality by 2025, no provisions for SES improvements were made [28][29][30]. Making matters worse, the deficiency in access is frequently accompanied by lack of programs that promote adherence to those medications. Unless significant changes are made in leveling both equity and SES soon, World Health Organization (WHO) targets of 50% use of essential medicines by 2025 will not be reached [30,31].

Population versus Individual Approaches-Revisiting Geoffrey Rose
The conceptual and theoretical foundation of population prevention is based on physician-epidemiologist Geoffrey Rose's hypothesis that the most effective means of harnessing prevention is to shift the population distribution of risk factors to the left (Figure 2 and Table 2) [32]. Rose postulated that differences in the distribution of risk factors among populations have more influence upon cardiovascular mortality than the differences between individuals within the same population; further, that the subpopulation at low-to medium-risk gives rise to more cardiovascular deaths than those at high-risk, since the former is a vastly larger subgroup [7,32]. Although some circumstances have changed and Dr. Rose's views have been challenged, his population strategy remains valuable to improve overall population health and reduce social inequalities in the instant application [28]. The SDH interventions contemplated will shift the population distribution to the left without changing the shape of the curve, because they are not superficial, but fundamental and structural, addressing the context or circumstances within which behavior occurs, rather than upon individual agency [2,33,34]. Dr. Rose was also cognizant of using absolute, rather than relative risk measurements [35]. Since relative inequalities may be greater if a health factor is lower in prevalence, but absolute inequalities will remain low at both extremely high or low levels of prevalence, consistency in use of absolute values is emphasized [2,36].

The Chronic Care Model
The acute care model of managing disease developed and was matched to illnesses common in the past century, typically pretransition ailments such as infections and trauma [7]. Rapidly growing prevalence of chronic, degenerative "Diseases of civilization" have now extended globally to affect non-Western countries as "noncommunicable diseases" (NCDs). These diseases develop over longer latency periods, involve multiple contributory "causes", require different diagnostic approaches, skill sets, multimechanistic therapies and monitoring, and frequently risk polypharmacy with attendant complications. One recurring fault in the health care system is multilevel fragmentation, in contrast to comprehensive, seamlessly integrated and sustainable care [37,38].
Chronic illness is defined by the need for continuing patient adjustments through interactions with a health care system. Most of the morbidity and mortality worldwide are now consequences of chronic diseases. In the U.S., as prevalence of multimoribities grows, chronic care accounts for an increasingly larger portion of health care resources. Initial contributions to the revisionist movement included the development of the chronic care model (CCM) in the 1990s, followed by growing interest and support of additional investigators and orgnizations [38][39][40][41]. The model envisioned uniting a systematic evidencedbased practice and guidelines for patient-centered chronic care to improve efficiency, outcomes, and cost between informed and motivated patients interacting with proactive, trained practice teams [37,38].
Focusing upon 6 interrelated components: Self-management support, delivery system redesign, clinical information systems, decision support, health care organization, and community resources, the model maintained that their improvement goals could be produced through system reform [37]. The literature reveals that successes were established using the CCM in some outcomes related to diabetes, hypertension, congestive heart failure, and asthma [38,39].
The WHO published its Innovative Care for Chronic Conditions to extend the CCM to NCDs [40]. The writers recognized a different type of care system was required, and addressed 8 essential elements for action in managing chronic care: Support a paradigm shift, manage the political environment, build integrated health care, align sectorial policies for health, use health care personnel more effectively, keep patient-centered care all-inclusive, involve the community, and assign prevention a high priority [40].
A final topic which has been the subject of much recent investigation, but yet remains in its infancy, is the extensive nature of how SDH and all lifestyle events influence health through epigenetic mechanisms. An understanding of epigenetic reprogramming may explain trends in cardio metabolic disease, but currently the extent and details are largely unknown. As big data analysis furthers precision medicine, perhaps the intersection of these domains will grow and offer useful therapeutic targets through which patient care may be improved.

Conclusion
The chronic care model is best suited for the management of the prevalent and costly diseases of civilization most nations face. The need for acute care will always persist, and hence the two approaches are not mutually exclusive. However, in order to improve control of cardiovascular risk, interventions with an exclusively clinical and individual scope are insufficient [7,26,34].
Continuing to conceptualize these choices as dichotomous may imperil an important opportunity which should not be overlooked. The corollary, CVR management should always take into account the balance between the clinical and public health approaches, was evident in the forging of the first International Consensus on mild hypertension with low to moderate CVR [2].
Achieving equity between and within countries to allow sufficient access to proven, basic therapies is an essential prerequisite for success in achieving international health goals. The great challenge of prioritizing and implementing cardiovascular preventive strategies will always is the optimal integration of all strengths and preventive opportunities available in society. Since risk factors now include SDH, it is even more apparent all options have not been employed, leaving immense potential unfulfilled. Motivation, collaboration, resolve, and persistence by all stakeholders are essential [41]. These assets transcend the boundaries of the health sector, and require the conscious and unconditional support of all facilities, particularly governmental agencies and non-governmental organizations [2,3,7,8,22,26,24,31,34,37].