for Black Americans carry a special burden. Moreover, societal discriminatory practices, like redlining to support residential segregation, have affected racial/ethnic minorities and are a fundamental cause that must be understood in order to reduce health disparities.
1.3.3 Health Disparities and Health Disparities Research
NIMHD defines a health disparity as a health difference, based on one or more health outcomes, that adversely affects defined disadvantaged populations. According to the legislation that created NIMHD, a health disparity population is characterized by a pattern of poorer health outcomes, indicated by the overall rate of disease incidence, prevalence, morbidity, mortality, or survival in the population as compared to the health status of the general population. NIH‐designated health disparity populations were defined in this legislation and the authority to modify these designations was given to the director of NIMHD in consultation with the director of the Agency for Healthcare Research and Quality (AHRQ). Currently designated health disparity populations include the racial/ethnic minority groups mentioned above, populations of less privileged SES or poor persons from any race/ethnic group, under‐served rural populations, and sexual and gender minorities. Health disparities research is devoted to (i) understanding determinants that cause, sustain, or mitigate health disparities; and (ii) how this knowledge is translated into interventions to reduce disparities.
NIMHD's definition of health disparities emphasizes an adverse difference in populations with a social disadvantage. From the NIMHD perspective, a defined difference in health outcomes between populations is not necessarily a disparity. We define disparity as a difference between a disadvantaged population and a more advantaged referent population or the general population.
By comparison, in Healthy People 2020, the contributions of social determinants to an individual's ability to achieve good health also include sex, age, and disability.3 Healthy People 2020 defines a health disparity as “a particular type of health difference that is closely linked with social, economic, and/or environmental disadvantage.” The NIMHD definition emphasizes the disadvantage of population groups, and thus all adverse health outcomes within the designated population groups are considered health disparities. The NIMHD definitions also emphasize the importance of the historical or current link to discrimination or exclusion in determining health and healthcare disparities. The contributions of biological mechanisms, healthcare access and quality, and interventions to ameliorate disparities also need to be considered.
1.3.4 Is It Minority Health or Health Disparities?
There is substantial overlap in minority health research and health disparities research, in particular, research that focuses on worse health outcomes among particular racial/ethnic minority groups compared to Whites or other populations (Figure 1.1). For example, the fact that African American men have a higher prevalence and mortality for lung cancer is both a minority health and health disparities issue [4]. Blacks are a disparity population, smoke at a similar or lower rate than other racial/ethnic groups, and yet experience up to 50% more lung cancer for the same cigarette smoking intensity [4].
Figure 1.1 Overlapping but distinct constructs of Minority Health and Health Disparities Research.
Another example is type 2 diabetes, which is more common and has more severe manifestations in all racial/ethnic minority groups studied in the United States compared to Whites [5]. However, within a staff model healthcare system, the rates of myocardial infarction or heart attacks in patients with diabetes were lower for all minority race/ethnic groups compared to Whites, while the rates of end‐stage renal disease were higher. Understanding the factors that lead to these substantial differences in outcomes by race/ethnicity in a well‐characterized disease such as diabetes are likely to advance knowledge about mechanisms of how the condition progresses [6].
There are conditions where some racial/ethnic minority groups may have better health outcomes than the reference population, placing the study of these conditions within the domain of minority health research. Latinos or Hispanics have the longest life expectancy by gender of any other demographic group in the United States. This longer life expectancy is a consequence of lower overall rates of cardiovascular disease, cancer, and cerebrovascular disease [7]. Suicide and opioid overdoses are other examples of conditions with lower rates for African Americans, Latinos, and Asians, but higher rates among American Indians/Alaska Natives and lower SES and rural Whites [8]. Research related to the last two populations would fall squarely into the category of health disparities research.
1.3.5 Standardized Measures of Minority Health‐ and Health Disparities‐Related Constructs
Evaluation of health disparities by SES requires a consistent and reliable approach. Household income is a powerful predictor of overall mortality in the United States, with those at the poverty level (defined as ≤ $25 000 household income per year) being three times more likely to die from any cause compared to the mortality rate among persons in a household with an income ≥ $115 000 per year (Figure 1.2) [9]. Although household income is a useful measure of SES, formal years of education may be simpler to obtain, more reliable and stable over the life course, and overall more efficient. Education may also be incorrectly reported, and years of schooling do not equate to quality of education. Thus, depending on the research question at hand, multiple indicators of SES may be the best strategy [10]. This relationship of SES measures and health outcomes is most robust for Whites and Blacks, but there is evident interaction between SES and race/ethnicity that needs to be inherent in most studies focused on minority health and health disparities.
Figure 1.2 Relative risk of all‐cause mortality by US annual household income level.
Although health disparities are usually related to SES and traditional minority race/ethnic groups, people living in rural areas are also a minority in their own way. There is increasing evidence of disparities from the leading causes of death among persons living in the most rural areas compared to those living in cities and these disparities merit increased research attention [11]. The operational definition of rurality used in data reported from the Centers for Disease Control and Prevention categorized about 18% of the US population as residing in rural counties. NIMHD endorses this definition and encourages researchers to examine the intersectionality of rural residence, less privileged SES, and race/ethnic minorities.
The addition of sexual and gender minorities (SGM) as a health disparity population is expected to lead to more innovative research to examine health determinants that contribute to disparities. SGM populations share the experience of discrimination with other disparity populations. This implies that there may be shared mechanisms of health determinants to specific conditions that can be examined. Although sexual orientation and gender identity questions are more recent additions to national surveys, it is clear that how these questions are asked significantly affects how respondents identify themselves. More research is needed to understand the best ways to assess sexual orientation and gender identity.
In comparing outcomes across populations, it is important to use standard terminology. Disease or condition rates, important aspects
