The Interplay of Socioeconomic Status and Risk for Heart Disease

Written by: Robert Philibert MD PhD
 
Socioeconomic status (SES) is a complex construct that combines variables such as education, income and occupation into a single variable.  Although researchers can parcel SES into dozens of distinct levels, for most purposes, SES can be conceptualized as being high, medium or low.  In the United States,  individuals typically with high SES are often physicians, lawyers or business leaders, while those with low SES are frequently unemployed or students.

Over the past decade, the public has become increasingly aware that the risk for disease is associated with SES status.  Historically, this has always been the case.  The Antonine and Cyprian plagues that ravaged ancient Rome were particularly devastating among the poor who lived in tightly clustered dwellings near the city center while sparing the elite that lived in the luxurious villas in the surrounding countryside.1 These plagues, which were promulgated by crowding and poor sanitation led to the development of the first sewage systems in the World. However, less appreciated is the role that poor diet and other SES related factors played in increasing the vulnerability of the poor to these infectious diseases.

Leaping forward 2000 years, we find ourselves embroiled in yet another global pandemic.  Like the prior plagues, the COVID19 pandemic is particularly deadly to those with low SES.  But even prior to the current onslaught, researchers have been documenting the relationship of SES to the rate of cardiovascular disease (CVD) in the United States. For example, a recently published study by Zhang and colleagues examined the relationship of SES to CVD disease burden and mortality in large research populations from the US (n=44,462)  and Great Britain (399,537).2  They found that in both the United States and Britain, those of low SES were twice as likely to die of CVD than those of high SES.  Sadly, these findings are not particularly surprising with these and similar prior findings 3 have caused universal concern in leaders of every strata of American society and for calls for actions to eliminate these health disparities.  The real question is “how?”

In order to understand how to address these disparities, it is first necessary to understand the etiology of heart disease.  Heart disease and CVD, in general, result from the interplay of genetic and environmental factors-in other words, based on their individual genetic profile, each of us are vulnerable to some environmental risk factors, but not others.  Thanks to the advances funded in large part by the National Institutes of Health, scientists have defined much of the genetic variation that underlies risk for CVD.  But according to a recent large scale genotyping study that included data from 300,000 subjects, only 16% of all risk for CVD results from heritable factors.4 Instead, the vast majority of vulnerability to illness results directly from the environment and its interplay with genetic factors.  In the study by Zhang and associates, they found unhealthy lifestyles mediated a small proportion of the differential vulnerability.  Instead, they suggested other factors such as access to healthcare may be to blame and noted strong interactions between lifestyle factors and SES with mortality.  In layman’s terms, better access to preventive care, both medical and non-medical, and education on how to practice healthy lifestyles, could have a big impact.

How do we attain and maintain healthy lifestyles? The American Heart Association lists the following lifestyle factors as risks for heart disease.

  • Smoking
  • Sedentary Lifestyle
  • High stress
  • Poor diet

They also recommend that Americans avoid Heart Disease by:

  • Exercising moderately at least 2 to 3 hours each week.
  • Eating healthy foods.
  • Not smoking and avoiding second-hand smoke and other pollutants.
  • Engaging in regular health care screenings.

 
However, a brief perusal of these recommendations will reveal that the ability to comply with these recommendations is tied to SES.  For example, for middle aged adults with families, the ability to exercise is associated with both access to gym/recreation facilities and access to child care.  One cannot go to the gym and leave a small child unmonitored. Similarly, obtaining a healthy diet can be expensive.  A single trip to the grocery store to purchase a week’s supply of the green leafy vegetables fresh fruit and lean meat products favored by dieticians for a family of four can easily exceed $300. 6 Availability of tobacco products is the single largest predictor of smoking status.  Yet, stores selling tobacco are located near low SES and African American neighborhoods. 7 As a result, poor children are more likely grow up exposed to cigarettes while rich children do not.  Finally, despite the progress of the past decade, many Americans lack the health insurance that would cover even the most basic routine screenings for heart disease.  As a result of each of these and other risk factors being associated with SES, SES itself is tied to risk for CHD.  What is more, because being ill is expensive for a family, having CHD in a parent is a risk for low SES in their offspring.  As a result, factors that ultimately are environmental can appear to be transmitted in family.

What can we do about these disparities?  The answer is actually quite a bit and we all can potentially gain by these efforts.

  • Be an advocate for access to recreation in your community-and your neighbors as well.  Sponsor a bike trail. Insist that new housing developments include parks and recreation facilities.
  • Healthy diets start early.  Encourage healthy diets and nutritional education in the young hearts and minds in our schools.
  • Incentivize smoking cessation and remove easy access to cigarettes in grocery stores and convenience stores.
  • Exercise routinely-and take a friend when you do!  It can decrease stress and strengthen friendships.
  • Advocate for others. A just mind sleeps well.

 
Finally, in noting the Antonine plagues, the Roman Emperor Marcus Aurelius lamented that that even the Antonine plague itself was less deadly than the “falsehood, evil behavior and lack of true understanding” around him.8 When he died, his last words were reported “weep not for me, think rather of the pestilence and the deaths of so many others”.  Two millennia later, as we struggle to emerge from our pandemic, may we grasp the torch of reform of  our common condition to provide equitable care for all and remember that while we complete our life journeys know that on this Earth  “ God’s work must truly be our own”. 9
 
References:

  1. Stange, N. Politics of Plague: Ancient Epidemics and Their Impact on Society. (2021).
  2. Zhang, Y.-B., et al. Associations of healthy lifestyle and socioeconomic status with mortality and incident cardiovascular disease: two prospective cohort studies. BMJ 373, n604 (2021).
  3. Simons, R.L., et al. Economic hardship and biological weathering: The epigenetics of aging in a U.S. sample of black women. Social Science & Medicine 150, 192-200 (2016).
  4. Hou, K., et al. Accurate estimation of SNP-heritability from biobank-scale data irrespective of genetic architecture. Nature genetics , 1 (2019).
  5. Association, A.H. Steps to improve heart health during the pandemic.  (2020).
  6. Hellmich, N. Cost of feeding a family of four: $146 to $289 a week. in USA Today(Maribel Perez Wadsworth  on behalf of Gannett, New York, 2013).
  7. Lee, J.G.L., et al.Inequalities in tobacco outlet density by race, ethnicity and socioeconomic status, 2012, USA: results from the ASPiRE Study. Journal of Epidemiology and Community Health 71 , 487-492 (2017).
  8. Aurelius, M. Meditations IX.2.  (Penguin, New York, 1981).
  9. Kennedy, J.F. Inaugural Address: January 20, 1961. J. Pub. L. 12, 235 (1963).
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