Rethinking Vulnerable Populations in the United States: An ...

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Shi et al.: Rethinking Vulnerable Populations in the US

Rethinking Vulnerable Populations in the United States: An Introduction to a General Model of Vulnerability Leiyu Shi, Dr.PH, MPA, MBA , Gregory D. Stevens, PhD, MHS, Pegah Faed, MPH, Jenna Tsai, Ed.D

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he United States has experienced and, at times, promulgated a long history of inequality among its citizens. From civil rights violations and suffrage restrictions that only started to resolve in the past 60 years, to increasing income gaps between the poor and rich through the early 21st century, inequality continues to pervade many aspects of modern life including education, employment, housing and other life necessities. Most deeply affected have been groups delineated by race or ethnicity, socioeconomic status, immigration status, culture and language, and sexual orientation.1 Perhaps the most persistent manifestation of inequality has been an ongoing and, in some cases, increasing disparity in health and wellbeing across these social divisions. Today it is not considered surprising to see major health differences between whites and AfricanAmericans, the wealthy and poor, or the insured and uninsured. But perhaps it

should be more surprising, considering that most health disparities are not caused by the lack of sanitation, poor drinking water, or famine that claimed the lives of many of this nation’s underprivileged in earlier years.2 Things, in fact, have changed dramatically. The causes of health disparities are not always obvious and, as we are starting to better understand, are rooted very deeply in the social context surrounding modern life.3 The medical professions are beginning to unravel and understand the impact that personal social position and social class, racism and discrimination, social networks, and other more relational community factors have on population health. Some of this knowledge has been applied to design interventions to address health disparities, but most efforts are in their infancy.4 Theory regarding vulnerable populations has dominated the social science and public health literature, but is

Dr. Leiyu Shi is a Professor of health policy and health services research from Johns Hopkins University Bloomberg School of Public Health Department of Health Policy and Management. He is Co-Director of Johns Hopkins Primary Care Policy Center. Dr. Shi’s research focuses on primary care, health disparities, and vulnerable populations. Dr. Shi is also well known for his extensive research on the nation’s vulnerable populations, in particular community health centers that serve vulnerable populations, including their sustainability, provider recruitment and retention experiences, financial performance, experience under managed care, and quality of care. Vol. 9, No. 1, Spring 2008 43

Features needed in the medical sciences as well.5 The purpose of this commentary is to summarize existing models regarding vulnerable populations and describe a more comprehensive general model that, while previously applied to the field of public health, can be applied to the medical field to guide the collection and reporting of health data, and the design of health interventions to serve vulnerable populations. Why Should Medical Professionals Focus on Vulnerable Populations? There are several overarching reasons that health professionals should focus on reducing health disparities. First, the US was founded on the principal of equality and freedom. Personal health, however, has remained conspicuously absent from the list of advocated civil rights. If equity is indeed a guiding principle for the US., then it may be argued that disparities in health should not be allowed to persist. Second, the health of the overall US population is far behind that of many other developed countries. For example, infant mortality, a common barometer of population health, remains substantially higher in the US than in thirty other countries (e.g. a rate of 6.9 deaths per 1,000 live births vs. 2.8 deaths per 1,000 births in Sweden).6 Achieving a similar level of health in the US cannot likely be attained without attention to the most vulnerable populations. Third, the number and proportion of vulnerable individuals is increasing in the US. For example, the national poverty rate reached 12.3% in 2006 (reflecting over 36.5 million individuals). Similarly, the uninsured population, increasing steadily since 1990, 44 Harvard Health Policy Review

reached about 15.8% of the population (or 47 million people) in 2006.7 As these groups grow, they place greater demands on the publicly-funded healthcare system and require greater policy attention. Existing Models for Understanding Vulnerability Studies of vulnerable populations have used many different theories or models to examine why vulnerable groups experience poorer health. Most of these have focused on a single explanatory factor (e.g. the lack of insurance on access to care) but have begun to acknowledge the multifaceted nature of vulnerability. The models are dichotomized as those that focus on: 1) attributes of individuals as causes of poor health, and 2) broader influences of communities on health. Individual-level models suggest that vulnerability stems from lacking inherent material and social resources that are essential to well-being. Individuals who lack these resources (e.g. income, education, health insurance) have a greater risk of poor health. Individuallevel models frequently tie the absence of these personal and social resources to higher rates of risk behaviors and lower rates of health promoting behaviors.8, 9 For example, vulnerable groups may eat unhealthfully because they lack the income (i.e. material resource) or education (i.e. social resource) to obtain healthful foods.10 Community-level models focus additionally on the omission from individual-level models that material and social resources are greatly affected by personal surroundings.11 For example, families will encounter difficulty ob-

Shi et al.: Rethinking Vulnerable Populations in the US taining a livable wage if few stable and well-paying jobs exist in the community, fewer students will graduate from high school or attend college if there are no well-funded schools and affordable colleges nearby, and people will not be able to access medical services if few providers practice nearby and if they do not accept Medicaid or other relevant insurance products. A General Model of Vulnerability The next evolutionary step that we propose requires the explicit recognition of the convergence of these individual and community risks that lead to vulnerability. We have developed a more “general” model (see Figure 1) to highlight the contributions of and the interactions between individual and community risks.1 Risks are categorized as predisposing, enabling, and need as defined by Andersen and Aday.12

Distinctive Characteristics of the General Model The general model of vulnerability has a number of distinctive characteristics. First, it is a comprehensive model including both individual and community level risks. One’s vulnerability is determined by the interactions between individual and community, such that the determinants of vulnerability may be beyond individual control. This avoids a tendency to “blame the victim” and highlights the importance of societal intervention. Second, the model focuses on attributes of vulnerability for the total population rather than focusing on subpopulations. While it recognizes individual differences in exposure to risks for certain conditions, there are common or crosscutting traits affecting many vulnerable sub-populations. This calls for a more integrated approach to reducing disparities that targets the most common vulnerability traits in the community.

Figure 1. A General Model of Vulnerability

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Features Third, a major distinction of the model is the emphasis on convergence of risks that have additive or multiplicative impacts on health. Examining vulnerability status as a multi-dimensional construct can reveal gradient relationships between vulnerability and health outcomes, and improve our understanding of patterns of health disparities. Application of the General Model to Hypertension To describe how the general model can be applied in medicine, we begin with the well-known disparity that African American men experience a disproportionately high rate of hypertension, a key factor in cardiovascular disease. In 2003, nearly one-in-three African American adults (~32%) reported they had hypertension compared to 20% of whites, 19% of Latinos, and 16% of Asians.2 Predisposing risks include a slight genetic predisposition for hypertension among African Americans.13 Community predisposing risks include being more likely to live in inner-city areas with fewer parks and recreation areas for regular exercise, and fewer and less accessible grocery stores with greater nutritional resources.14-16 African-Americans are more likely than other groups to be employed in lower wage and bluecollar jobs that contribute to higher stress levels,17, 18 and perceive higher levels of discrimination, which is thought to be a form of chronic stress and has been associated with hypertension.19-21 Enabling risk factors for hypertension include the individual lack of income that affords individuals the ability to buy hypertension-protective goods and services such as healthy foods, 46 Harvard Health Policy Review

organized recreational activities, and leisure time away from work. Lack of health insurance limits regular access to healthcare services that may prevent or treat hypertension.22, 23 At the community level, low-income areas offer few well-paying jobs with health insurance, and medical providers are less likely to practice in these areas.24 African Americans are more likely to experience these risk factors.25 Taken together, these predisposing and enabling risk factors combine to affect the likelihood that African Americans will have hypertension (see Figure 2). According to the model, hypertension rates are higher among African Americans because 1) they have a predisposition for hypertension, 2) live where stressors are higher and opportunities for health promotion are fewer, and 3) are less likely to have access to healthcare services to prevent and treat hypertension. The general model focuses on the complement of risk factors that, together, contribute the presence of this problem. Implications for Public Health, Medicine, and Policy Understanding the contributors to health in this way suggests that singlepronged interventions will be less effective than those that target multiple risks. For public health professionals, this means designing data collection strategies to monitor these critical risk factors and implementing programs that cross sectors (e.g. health promotion that focuses on educating individuals about hypertension prevention and educating private and public sector officials about urban design in low-income communities).

Shi et al.: Rethinking Vulnerable Populations in the US

Figure 2. General Model Applied to Hypertension Rates Among AfricanAmericans For medical providers, this means understanding the context of these risk factors, and intervening where possible (e.g. extending access for vulnerable populations and efforts to reach vulnerable patients for screening and treatment). For policy-makers, this model suggests that existing categorical approaches to program funding for vulnerable populations are inefficient and uncoordinated. Instead of funding programs for separate conditions and subpopulations, it may be more efficient to fund programs that target a range of risk factors that are common across priority health disparities. In conclusion, the general model is one tool that professionals in public health, healthcare, and policy may use to better understand and resolve disparities. Because of the complexity of risk factors that contribute to poorer health of vulnerable populations, a model that is designed to focus explicit attention on the combination of key risk factors may help to unite these fields as they

continue to document and resolve disparities. References 1. Shi L, Stevens GD. Vulnerable Populations in the United States. San Francisco, CA: Jossey-Bass; 2005. 2. National Center for Health Statistics. Health, United States 2005. Hyattsville, Maryland: Centers for Disease Control; 2006. 3. Banks J, Marmot M, Oldfield Z, Smith JP. Disease and disadvantage in the United States and in England. Jama. May 3 2006;295(17):2037-2045. 4. Cooper L, Hill M, Powe N. Designing and evaluating interventions to eliminate racial and ethnic disparities in health care. J Gen Intern Med. 2002;17:477-486. 5. Mechanic D, Tanner J. Vulnerable people, groups, and populations: societal view. Health Aff (Millwood). Sep-Oct 2007;26(5):1220-1230. 6. National Center for Health Statistics. Health, United States 2006. Hyattsville, Maryland: Centers for Disease Control;

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Features 2007. 7. DeNavas-Walt C, Proctor B, Smith J. Income, Poverty, and Health Insurance in the United States: 2006. Washington, DC: U.S. Census Bureau; August 2007. P60-233. 8. Power C, Matthews S. Origins of health inequalities in a national population sample. Lancet. Nov 29 1997;350(9091):1584-1589. 9. Lantz PM, House JS, Lepkowski JM, Williams DR, Mero RP, Chen J. Socioeconomic factors, health behaviors, and mortality: results from a nationally representative prospective study of US adults. Jama. Jun 3 1998;279(21):1703-1708. 10. Aday LA. Health status of vulnerable populations. Annu Rev Public Health. 1994;15:487-509. 11. Flaskerud JH, Winslow BJ. Conceptualizing vulnerable populations healthrelated research. Nurs Res. Mar-Apr 1998;47(2):69-78. 12. Andersen RM. Revisiting the behavioral model and access to medical care: does it matter? J Health Soc Behav. Mar 1995;36(1):1-10. 13. Brandon DT, Whitfield KE, Sollers JJ, 3rd, et al. Genetic and environmental influences on blood pressure and pulse pressure among adult African Americans. Ethn Dis. Spring 2003;13(2):193-199. 14. Schulz AJ, Williams DR, Israel BA, Lempert LB. Racial and spatial relations as fundamental determinants of health in Detroit. Milbank Q. 2002;80(4):677-707, iv. 15. Schulz A, Northridge ME. Social determinants of health: implications for environmental health promotion. Health Educ Behav. Aug 2004;31(4):455-471. 16. Diez Roux AV, Merkin SS, Arnett D, et al. Neighborhood of residence and incidence of coronary heart disease. N Engl J Med. Jul 12 2001;345(2):99-106. 17. Marmot MG, Bosma H, Hemingway H, Brunner E, Stansfeld S. Contribution of job control and other risk factors to social variations in coronary heart disease incidence. Lancet. Jul 26 1997;350(9073):235-239.

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18. Bosma H, Marmot MG, Hemingway H, Nicholson AC, Brunner E, Stansfeld SA. Low job control and risk of coronary heart disease in Whitehall II (prospective cohort) study. Bmj. Feb 22 1997;314(7080):558-565. 19. Din-Dzietham R, Nembhard WN, Collins R, Davis SK. Perceived stress following race-based discrimination at work is associated with hypertension in AfricanAmericans. The metro Atlanta heart disease study, 1999-2001. Soc Sci Med. Feb 2004;58(3):449-461. 20. Davis SK, Liu Y, Quarells RC, DinDzietharn R. Stress-related racial discrimination and hypertension likelihood in a population-based sample of African Americans: the Metro Atlanta Heart Disease Study. Ethn Dis. Autumn 2005;15(4):585-593. 21. Cozier Y, Palmer JR, Horton NJ, Fredman L, Wise LA, Rosenberg L. Racial discrimination and the incidence of hypertension in US black women. Ann Epidemiol. Sep 2006;16(9):681-687. 22. Lurie N, Ward NB, Shapiro MF, Brook RH. Termination from Medi-Cal--does it affect health? N Engl J Med. Aug 16 1984;311(7):480-484. 23. Lurie N, Ward NB, Shapiro MF, Gallego C, Vaghaiwalla R, Brook RH. Termination of Medi-Cal benefits. A follow-up study one year later. N Engl J Med. May 8 1986;314(19):1266-1268. 24. Smedley B, Stith A, Nelson A, eds. Unequal Treatment: Confronting Racial and Ethnic Disparities in Health Care. Washington, DC: National Academy Press; 2002. 25. DeNavas-Walt C, Proctor B, Lee C. Income, Poverty, and Health Insurance in the United States: 2005. Washington, DC: U.S. Census Bureau; August 2006. P60-231.