Introduction

Cardiometabolic disorders (CMD) that affect cardiovascular and metabolic functions are the leading cause of morbidity and mortality worldwide [1]. The range of such CMD extends from cardiovascular diseases (CVD; such as hypertension, stroke, and coronary artery disease) to diabetes mellitus (type 2 diabetes), obesity, chronic kidney disease, and non-alcoholic fatty liver disease. Notably, CMD exacerbates the mortality risk from emerging illnesses, such as COVID-19 [2]. Prevention of this set of diseases could therefore significantly lessen disease burden and mortality risk across the world. Although many biological risk factors for CMD have been identified, recent work has shown that a large proportion of such disease could be attributed to environmental factors, influenced by social networks and socioeconomic status [3]. In addition, demographic analyses of CMD prevalence show marked disparities, with significant differences in incidence and outcomes, among racial/ethnic minority groups [4,5,6,7]. For example, in the United States, African Americans are approximately twice as likely to develop CMD and die from CMD complications in comparison with Whites [8]. African Americans also are twice as likely to have hypertension [9], Type 2 Diabetes (T2D) [10], and CVD [11]. Similarly, other racial/ethnic minority groups are disproportionately affected by CMD. Higher rates of CVD and T2D have been reported in Hispanic/Latino [12] communities, and South Asian ancestry has been found to be associated with a higher risk for CVD-related mortality [13]. Given the high rates of CMD-related mortality and morbidity among racial/ethnic minorities, identifying key factors contributing to these health inequities, such as racial/ethnic discrimination, is critical for supporting, enhancing, and developing effective prevention strategies.

The multifactorial nature of CMD suggests that, in addition to weak genetic influences, an array of environmental factors, such as features of the social environment, diet, lifestyle, and socioeconomic status, may be important determinants of disease risk [14]. Although several individual risk and lifestyle factors have been identified as key drivers of CMD risk, structural and interpersonal circumstances also can influence CMD risk, and predispose racial/ethnic minority groups to adverse CMD outcomes [11, 15]. Although such psychosocial and structural health barriers may be linked to racism and racial/ethnic discrimination [5, 16], neither their contribution nor the underlying mechanisms are well understood.

Previous work has shown that racism, structural and systemic practices that assign value to people based on the color of their skin [17], and racial discrimination, unfair treatment on the basis of skin color or perceived membership in a racial group [18], are critical determinants of health outcomes [17,18,19]. Experiences with racism and racial discrimination can be stress-inducing [20], which could have negative implications for cardiometabolic health among racial/ethnic minorities [21,22,23]. Psychosocial stress due to racial discrimination has been hypothesized to contribute to disparities in CMD incidence among racial/ethnic minority groups [4, 5], and several physiological mechanisms underlying the association between racial/ethnic discrimination and CMD have been proposed. These include discrimination stress-induced activation of the autonomic nervous system triggering the release of cortisol and catecholamines, resulting in increased blood pressure and cardiovascular reactivity [24, 25]. Also, chronic stress due to discrimination can increase inflammation [26] and allostatic load, resulting in wear and tear on bodily systems increasing the risks of CMD [27]. However, the roles and contributions of these factors are not well understood, and further work is required to gauge the full impact of discrimination on physiology, hemodynamics, and metabolism.

Such assessments of risk would be greatly facilitated by the identification of specific biomarkers that would be useful not only in identifying the physiologic contribution of discrimination exposure but also for developing more targeted approaches in primary and secondary CMD prevention [28]. Elucidation of such biomarkers could also aid in the identification of high-risk individuals, accurate diagnoses and prognosis of CMD, and monitoring the burden of disease [28, 29]. Therefore, identifying CMD biomarkers sensitive to discrimination exposure has utility in increasing knowledge and in potentially improving the disproportionate burden of CMD borne by racial/ethnic minorities.

To delineate the contribution of discrimination to CMD risk and to identify informative biomarkers, it is critically important to evaluate the association between racial/ethnic discrimination and CMD. Systematic reviews of the association between perceived racial/ethnic discrimination and increased CVD risk [30] and hypertension [24, 31] have been previously conducted. However, the association of racial/ethnic discrimination with cardiovascular and metabolic disease has not been examined. Because the two diseases share common etiology (“shared soil” hypothesis), looking at them collectively is important as it may provide a more comprehensive assessment of the impact of discrimination than by examining either disease alone. Therefore, the aim of this systematic review is two-fold: 1) to examine what is known about the association between racial/ethnic discrimination and CMD among minority groups, and 2) to characterize CMD biomarkers sensitive to discrimination exposure.

Methods

Search Strategy

A comprehensive review of online databases was conducted in January 2021 and again in February 2023. This review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [32]. First, articles were identified using Boolean searches in five databases: PubMed, Google Scholar, WorldWideScience.org, ResearchGate, and Microsoft Academic. The search terms were “discrimination OR racism OR race-related stress AND cardiometabolic disease OR cardiovascular disease OR hypertension OR diabetes OR obesity OR chronic kidney disease OR coronary artery calcification”. Additionally, manual searches of reference lists of articles identified were performed.

Eligibility Criteria

We included articles that met the following inclusion criteria: (1) participants with diagnosed or self-reported cardiometabolic diseases, (2) published in English in a peer-reviewed journal, (3) included racial/ethnic minorities, (4) examined racial/ethnic discrimination/racism, and (5) conducted in the United States. Because the experience of racial/ethnic discrimination differs across nations and cultures, we restricted inclusion to studies conducted in the U.S.

Data Extraction

The search process identified 1,773 records, and reference cross-checks produced an additional 3 records for a total of 1,776 articles. Elimination of duplicates (n = 951) and articles with titles or abstracts irrelevant to the review (i.e., title and abstract did not include reference to discrimination and CMD, n = 656) resulted in 169 articles. Of these articles, 46 were excluded after failing to meet eligibility criteria (i.e., no CMD outcome, n = 14; racial/ethnic discrimination not assessed, n = 26; conducted outside the U.S., n = 6), yielding 123 eligible studies (Fig. 1).

Fig. 1
figure 1

Flow chart of article selection process

Results

Study Characteristics

The descriptive characteristics (study design, sample size, biomarkers, discrimination measure used, and associations found) of studies included are detailed in Table 1. Data from 343,268 participants were included in the systematic review, with sample sizes ranging from 32 to 45,781 participants. Eighty-seven of the studies were cross-sectional, 25 were longitudinal, 8 were quasi-experimental, 2 were randomized controlled trials and 1 was a case–control. The most commonly used discrimination measures were the Everyday Discrimination Scale (n = 40), Experiences of Discrimination Scale (n = 22), Perceived Racism Scale (n = 10), and Perceived Ethnic Discrimination Questionnaire (n = 11) (Supplemental Table 1).

Table 1 Characteristics of studies included

Discrimination and CMD Outcomes

Across these articles, African Americans/Blacks were the most often studied racial/ethnic group (53.1%), followed by Whites (33.5%), Hispanics/Latinos (9.3%), Asians (2.9%), Other (0.98%), Native Hawaiians/Pacific Islanders (0.2%) and American Indians (0.02%). Of the studies, 81 (65.8%) examined African Americans/Blacks, 29 (23.6%) examined African Americans/Blacks and Other races/ethnicities, and 13 (10.6%) examined other races/ethnicities only. Table 2 provides an overview of the CMDs and biomarkers examined. The most frequently examined CMDs were hypertension (n = 46) and CVD (n = 40). Other CMDs examined were diabetes (n = 11), obesity (n = 12), metabolic syndrome (n = 9), and chronic kidney disease (n = 5).

Table 2 Frequency and association of cardiometabolic disease and biomarkers across studies

Of the studies, 73.2% (n = 90) found that racial/ethnic discrimination was positively associated with a significant increase in CMD risk incidence (Table 1) [33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122]. Of the 87 studies using a cross-sectional design, 70.1% (n = 61) found a significant positive association with CMD. For example, Cardarelli et al. evaluated 510 adults from the North Texas Healthy Heart Study [42]. Participants who experienced racial discrimination and passively responded to unfair treatment were 3 times more likely to have coronary artery calcification (CAC) compared to those who did not report any experiences of racial discrimination [42].

Twenty-five studies employed a longitudinal design, with 76% finding a positive association. For example, Forde et al. conducted a longitudinal cohort study of 1,845 African American adults participating in the Jackson Heart Study [56] and found that lifetime experience with discrimination was associated with a higher incidence of hypertension [56]. Also, 7 of 8 (87.5%) quasi-experimental studies found a positive association between experiences of racial/ethnic discrimination and CMD. In addition, Tull et al. employed a case control design [99] and Merritt et al. and Arriola et al. utilized a randomized controlled trial [80, 110], with all finding a significant positive association between racial/ethnic discrimination and CMD. However, 33 (26.8%) articles found no significant association between experiences of racial/ethnic discrimination and CMD [123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155]. Hypertension (n = 16) was the most frequent CMD found to have no significant association with racial/ethnic discrimination, while CVD (n = 34) was the most frequent outcome positively associated with racial/ethnic discrimination. In the 33 articles that found no significant association between experiences of racial/ethnic discrimination and CMD [123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155], the total population (N = 60,422) was comprised of 49.5% African Americans, 33.3% Whites, and 17.2% Other races/ethnicities. The total population included adults aged 18–95 with a sample size range of 62–10,973 participants. SBP and DBP (n = 16) were the most frequent biomarkers examined, and the Everyday Discrimination Scale (n = 13) was the most frequently used discrimination measurement tool. In comparison, the 90 articles in which a significant association was found included a total population of 282,846 partipants, with sample size ranges of 32–45,781 participants. Most participants in these studies were African American adults, particularly African American women (56.4%), aged 18–95 [33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122].

Racial/Ethnic Discrimination and Biomarkers of CMD

Across the studies, a variety of CMD biomarkers were examined. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were the most frequently used (n = 52) biomarkers reported in cross sectional (n = 40), longitudinal (n = 7), quasi-experimental (n = 4), and randomized controlled trial (n = 1) studies (Table 2). C-reactive protein (CRP), a marker of inflammation, was one of the most frequently analyzed biomarkers (n = 12) in cross sectional (n = 5), longitudinal (n = 4), and quasi-experimental (n = 3) studies. Other biomarkers examined were body mass index (BMI, n = 17), heart rate (HR/HR variability, n = 13), fasting blood glucose (FBG, n = 9), hemoglobin A1c (HbA1c, a blood sugar marker, n = 6), coronary artery calcification (CAC, n = 3), leukocyte telomere length (nucleoproteins that cap chromosomes, n = 3), glomerular filtration rate (GFR, assesses kidney function, n = 3), plasma endothelin 1 (a vasoconstrictor peptide, n = 2), and Solute Carrier Family 4 Member 5 (SLC4A5 gene, associated with cardiometabolic phenotypes, n = 1).

Across several studies, a significant positive association between racial/ethnic discrimination and biomarkers of CMD was observed, with SBP and DBP (n = 38) found to be the most frequently associated with experiences of racial/ethnic discrimination, followed by BMI (n = 13), HR/HR variability (n = 10) and CRP (n = 9). Table 2 details the frequency and associations of CMD biomarkers and their distribution across study designs.

Discussion

This review provides an overview of the relationship between racial/ethnic discrimination and CMD among racial/ethnic minority groups in the United States. To the best of our knowledge, this review is the first to assess association between CMD and CMD biomarkers and to relate them to measures of discrimination. Overall, the evidence reviewed here suggests that there is a significant positive association between experiences of racial/ethnic discrimination and CMD, with 73.2% of studies finding significant links. Previous systematic reviews also suggest that there is a significant relationship between racial discrimination and cardiovascular health [24, 30]. One of the previous reviews identified 15 eligible articles (sample size range = 69–4,694 participants) exploring the association between racial discrimination and hypertension among African Americans, with 60% of the studies finding a positive association. Similarly, the other identified 84 articles (sample size range = 27–26,992 participants) examining the links between stigma/discrimination and CVD risk factors, with 86% of the studies finding a significant association among socially stigmatized/discriminated groups. The current findings corroborate and extend previous work reporting a strong positive association between discrimination and CVD risk [24, 30, 31]. The current review also examined CMD, expanding the focus to include metabolic dysfunctions, such as diabetes, obesity, chronic kidney disease, and metabolic syndrome. In addition, this review explored CMD biomarkers sensitive to discrimination as well as reviewed substantially more articles, increasing the overall population sample size, and additional measures of discrimination, with the majority of studies finding a positive association. Such results suggest that the processes that contribute to CMD are highly sensitive to significant stress and burden from experiences of racial/ethnic discrimination. Many of the studies included in this review were completed in the last decade, underscoring that racial/ethnic discrimination and CMDs remain pressing public health problems that need to be addressed.

Although studies with different racial/ethnic groups have been reported, African Americans were the most frequently studied group. Given that African Americans are the largest U.S. racial minority group [156], the frequency of CMD in African Americans, as well as the extent of racial discrimination and health inequities, this focus is important. However, important gaps in the literature remain. For example, there was limited evaluation of subgroup differences by race and ancestry, and there were few studies that examined in depth the impact of racial discrimination in many other racial/ethnic minorities, such as Hispanics/Latinos, Asians, Native Hawaiians, American Indians, and persons with multiple races. Additional work in these areas is urgently required.

Racism is embedded within structures and systems that support or facilitate experiences with discrimination. Dismantling such systems and structures is necessary to reduce exposure to discrimination, and thus aid in reducing CMD disparities borne by racial/ethnic minorities. Certainly, efforts to dismantle systemic racism should prioritize policy changes, ranging from creating new equitable policies to enforcing existing antidiscrimination laws [157]. Limited research has been conducted on the association of structural racism and/or systemic racial/ethnic discrimination and CMD, with the majority of studies in this review examining perceived experiences of discrimination. It is essential for future research to examine this association to improve understanding and inform policies that can eliminate systemic/structural barriers to optimum cardiometabolic health, as systemic and structural racism has been linked to adverse health outcomes [23].

Most studies were observational (Table 1); thus, causal effects cannot be determined. However, nineteen longitudinal studies [34, 36,37,38,39,40,41, 48,49,50, 52, 55, 56, 90, 100, 104, 108, 112, 115], seven quasi-experimental studies [60, 64, 70, 75, 77, 111, 118], and two randomized controlled trials [80, 110] provide supporting evidence for temporality and causation. Results of these studies were consistent with the cross-sectional findings; however, some observational studies found positive associations for African American women but not men [85] and an increase in diastolic but not systolic blood pressure [61, 72]. Also, many studies that did not find a significant association between racial/ethnic discrimination and CMD utilized small sample sizes, thus the potential for underpowered studies may explain these differences. This systematic review highlights the need for more longitudinal, prospective cohort, and randomized controlled trial studies to comprehensively measure experiences of racial/ethnic discrimination and establish links to CMDs over time. Specifically, studies that consistently employ large sample sizes and the same standardized measures and/or markers of racial/ethnic discrimination and CMD will be important going forward.

Our review of CMD biomarkers sensitive to racial/ethnic discrimination exposure can contribute to improving detection and understanding of the pathogenesis of CMD among racial/ethnic minorities. Consequently, such understanding may aid in the prevention of CMD and complications among racial/ethnic populations exposed to discrimination. Blood pressure and inflammatory biomarkers were most frequently associated with CMD related to experiences of racial/ethnic discrimination, supporting previous findings that chronic stress from racial/ethnic discrimination increases inflammation and results in wear and tear of bodily systems [26, 27]. Also, genetic and novel biomarkers, such as SLC4A5 gene [95], plasma endothelin 1 gene [59], leukocyte telomere length [74] and RBC heme degradation [94], were demonstrated to be potential predictors of CMD risks among racial/ethnic minorities who reported experiences of racial/ethnic discrimination. The objectivity and reliability of biomarkers support their increased use as risk assessment tools for predicting CMD due to experiences of racial/ethnic discrimination.

Limitations

Some limitations of the review warrant consideration. First, we only included studies published in English. Second, we employed specific search terms, used particular databases, and set a defined timeframe. Thus, expanding the search terms or including publications in other languages, from other databases, or after our timeline might yield additional articles not included in this review. Despite these limitations, the review employed over 100 peer reviewed publications to contextualize understanding of racial/ethnic discrimination-related CMD risk, with a focus on cardiometabolic biomarkers.

Conclusions

In summary, the existing literature suggests that experiences of racial/ethnic discrimination are associated with increased risk of CMD, with findings relatively consistent across varying study designs, samples, and measures. This result indicates that a culturally-sensitive approach to CMD prevention and one informed by the many ways racial/ethnic minorities experience discrimination is necessary. The inclusion of experiences with racial/ethnic discrimination in clinical assessment may be critical in detecting CMD early and in prevention or improved prognosis for racial/ethnic minorities.