The review, led by Marilyn Tseng of California Polytechnic State University together with Ashley Watt, Anna Ostrander, and Carolyn Fang of Fox Chase Cancer Center, synthesized 45 articles representing 34 unique studies examining what researchers call co-ethnic exposure, meaning residential exposure to others who share one’s racial or ethnic identity. The team searched PubMed and Web of Science for studies published through October 2023 that examined ethnic density or residential segregation in relation to three major cardiometabolic conditions: adiposity, cardiovascular disease, and diabetes. Study quality was assessed using the U.S. National Institutes of Health’s Quality Assessment Tool for Observational Cohort and Cross-sectional Studies.

The technical scope of the review was considerable. Of 1,813 articles initially identified, 1,080 remained after removing duplicates, and after rigorous screening by at least two reviewers per record, 45 articles representing 34 unique studies were included. Nine studies were longitudinal, following participants over time, while the majority were cross-sectional. Over half of the studies relied on self-reported outcomes rather than objectively measured ones. The most common exposure measure was the percentage of census tract residents sharing the participant’s racial or ethnic classification, though the review also captured segregation measures such as isolation and dissimilarity indexes, and local indicators of spatial association including the Getis-Ord statistic.

The headline finding is stark. Over 40 percent of studies including Black and Hispanic/Latine populations reported an association of greater co-ethnic exposure with poorer cardiometabolic outcomes, compared with only 7 percent of studies including Asian populations. Yet across all three groups, between 25 and 40 percent of studies reported inverse associations, meaning that higher co-ethnic exposure was linked to better health. This heterogeneity, the authors argue, reflects interactions among structural disadvantage, community stressors, and neighborhood resources rather than any inherent property of ethnic concentration itself.

Among Black populations specifically, twelve of 24 studies found a positive association between co-ethnic exposure and poorer cardiometabolic health, six found an inverse association, and five found no association. Longitudinal evidence from major U.S. cohorts proved particularly compelling. In the Multi-Ethnic Study of Atherosclerosis, segregation measured using the Getis-Ord local statistic was associated with a higher hazard of cardiovascular disease among Black participants, with a hazard ratio of 1.12 per standard deviation increase. In the Coronary Artery Risk Development in Young Adults study, a one-standard-deviation increase in segregation score was associated with a mean systolic blood pressure increase of 0.16 millimeters of mercury, and Black adults who moved from high to low segregation neighborhoods experienced reductions in systolic blood pressure of 1.48 millimeters of mercury compared with those who remained in high segregation areas.

Hispanic/Latine populations showed similarly mixed results. Eight of 19 studies reported a positive association, five an inverse association, and three no association, with three studies producing mixed findings that depended on nativity, neighborhood poverty, or the level of exposure. In one particularly striking example from the National Health Interview Survey, metropolitan-level segregation was protective for Hispanic immigrants in low-poverty neighborhoods but increased obesity risk for U.S.-born Hispanics in high-poverty neighborhoods. In the Hispanic Community Health Study/Study of Latinos, the isolation index was associated with higher odds of metabolic syndrome, with an odds ratio of 2.29 comparing the fifth to the first quintile, though the Gini coefficient showed no association.

Asian populations presented a distinctly different picture. Eight of 14 studies showed no association between co-ethnic exposure and cardiometabolic outcomes, five found an inverse association, and only one showed a positive association. All three longitudinal studies in this group showed no association. The single positive finding emerged for gestational diabetes among South Central Asian immigrant women in New York City, while the same study found no association for Chinese immigrant women. The authors note that studies in Asian populations remain critically scarce despite Asians comprising roughly 30 percent of immigrants to the United States, and that only one study included Pacific Island participants and one included American Indian or Alaska Native participants.

To interpret these heterogeneous findings, the review draws on the stress-exposure-disease model proposed by Gee and Payne-Sturges. In this framework, health outcomes in segregated environments result from the balance between community stressors and neighborhood resources, both shaped by historically based structural factors. Poorer cardiometabolic health may result when community stressors arising from concentrated disadvantage and resource deprivation outweigh neighborhood resources, whether through behavioral coping strategies such as smoking or poor diet, or more directly through stress-related mechanisms in which glucocorticoids affect the regulation and functioning of multiple physiologic systems. Conversely, protective associations may emerge if sharing an ethnic background with one’s neighbors contributes to feelings of connection and belonging, facilitates social support networks, improves access to culturally sensitive health services, and fosters collective efficacy.

The review also uncovered a notable pattern across measurement approaches. Among Black and Hispanic/Latine populations, studies using segregation-based measures more frequently reported adverse cardiometabolic associations than studies relying on measures of ethnic density, which more often yielded null findings. This suggests that different measures of co-ethnic exposure capture different dimensions of neighborhood context. The authors caution that investigators’ selection of a particular measure may itself be influenced by their understanding of the processes that led to co-ethnic exposure, resulting in more frequent selection of segregation measures in studies including Black populations. They also flag residual confounding from other aspects of neighborhood deprivation, over-adjustment if co-ethnic exposure affects health behaviors included as covariates, and the challenge of residential self-selection as key methodological concerns.

Looking forward, the authors call for more studies among Asian, Pacific Island, and Indigenous populations, objective rather than self-reported outcome measures such as wearable devices capturing heart rate and glucose levels, longitudinal designs with repeated exposure assessment, and explicit theoretical frameworks specifying mediating pathways. They argue that future research should disentangle ethnic density from immigrant concentration, examine how heterogeneity within groups such as immigration generation may modify effects, and consider the sociohistorical context that produced a given population’s residential patterns. On the policy side, the review suggests protecting community social structures through support for community-based organizations and cultural centers, preventing displacement through affordable housing policies, and building community control through participatory planning processes. The primary implication, the authors conclude, is to support conditions in which co-ethnic communities can collectively participate in decisions that generate health-promoting resources while reducing the structural disadvantages that undermine those resources.

Subject of Research: Public Health

Article Title: A systematic review of co-ethnic exposure and cardiometabolic outcomes in racial and ethnic minoritized populations

Article References: Tseng, M., Watt, A. S., Ostrander, A. K., & Fang, C. Y. (2026). A systematic review of co-ethnic exposure and cardiometabolic outcomes in racial and ethnic minoritized populations. Public Health Reviews, 47, Article 1609690. https://doi.org/10.3389/phrs.2026.1609690

Image Credits: AI Generated

DOI: 10.3389/phrs.2026.1609690

Keywords: cardiometabolic health, ethnic density, residential segregation, neighborhood effects, health disparities, systematic review, public health, minoritized populations, systematic, review, co-ethnic, exposure