Race and health profiles in the United States: an examination of the social gradient through the 2009 CHIS adult survey

Abstract

Objective

To examine the role of the social gradient on multiple health outcomes and behaviors. It was predicted that higher levels of SES, measured by educational attainment and family income, would be associated with positive health behaviors (i.e., smoking, drinking, physical activity, and diet) and health status (i.e., limited physical activity due to chronic condition, blood pressure, obesity, diabetes, BMI, and perceived health condition). The study also examined the differential effects of the social gradient in health among different racial/ethnic groups (i.e., non-Hispanic Whites, Blacks, Asian, Hispanics, and American Indians).

Study design

Cross-sectional study.

Methods

The data were from the adult 2009 California Health Interview Survey (CHIS). Weighted multivariable linear and logistic regression models were conducted to examine trends found between SES and health conditions and health behaviors. Polynomial trends were examined for all linear and logistic models to test for the possible effects (linear, quadratic, and cubic) of the social gradient on health behaviors and outcomes stratified by race/ethnicity.

Results

Findings indicated that, in general, Whites had more favorable health profiles in comparison to other racial/ethnic groups with the exception of Asians who were likely to be as healthy as or healthier than Whites. Predicted marginals indicated that Asians in the upper two strata of social class display the healthiest outcomes of health status among all other racial/ethnic groups. Also, the social gradient was differentially associated with health outcomes across race/ethnicity groups. While the social gradient was most consistently observed for Whites, education did not have the same protective effect on health among Blacks and American Indians. Also, compared to other minority groups, Hispanics and Asians were more likely to display curvilinear trends of the social gradient: an initial increase from low SES to mid-level SES was associated with worse health outcomes and behaviors; however, continued increase from mid-SES to high SES saw returns to healthy outcomes and behaviors.

Conclusion

The study contributes to the literature by illustrating unique patterns and trends of the social gradient across various racial/ethnic populations in a nationally representative sample. Future studies should further explore temporal trends to track the impact of the social gradient for different racial and ethnic populations in tandem with indices of national income inequalities.

Introduction

More than half a century ago, the Whitehall Study uncovered the relationship between social class and death from coronary heart disease among British civil servants.¹ Since the landmark study, the literature has continued to provide strong evidence for the phenomenon referred to as the social gradient in explaining incremental disparities in health status and conditions.2, 3, 4 The social gradient impacts health whereby members from the lowest levels of social class experience the worst health outcomes and members from the highest levels experience the best outcomes. Middle class members also experience poorer health status in comparison to those from the upper class. The social gradient effect has been demonstrated with various health conditions such as high blood pressure,⁵ obesity/body weight,6, 7 Type 2 diabetes,⁸ and general health and well-being.⁹ The social gradient has also been linked to a variety of health behaviors, including tobacco use,10, 11 alcohol and substance use,¹² physical activity,¹³ and dietary behaviors.7, 14

The term socioeconomic status (SES) is often used to capture social class and refers to social and economic factors that influence an individual's positions in society.15, 16 Group members with lower SES experience poor health outcomes due to a number of possible mechanisms. One pathway from SES to health is through differential exposure to environmental hazards.17, 18 Another proposed pathway highlights differential access,19, 20, 21 as health care access and other enabling factors (e.g., possession of health insurance and a regular provider) are associated with higher utilization of preventive and curative health services.22, 23, 24, 25, 26, 27, 28, 29 However, access to care does not entirely account for health inequality, demonstrated by existing disparities in health systems that utilize universal national insurance plans.28, 29 Disparate health outcomes are likely to arise from societal inequalities as well, underscored by a third pathway, which proposes that members from positions of lower SES endure a lifetime of exposure to institutionalized discrimination, prejudice in the medical system, and chronic stressors, resulting in maladaptive coping responses such as alcohol and substance abuse.30, 31

The structural organization of power and privilege is a driver for health inequities. In addition to the social gradient, health disparities research in the U.S. often examines health as experienced by various racial/ethnic groups with race serving as a proxy for social class.32, 33 Though race/ethnicity and social class are highly interrelated, the distribution of power and privilege operates independently and in concert with race/ethnicity to impact health.34, 35 Relying on the social gradient as the theoretical framework for the present paper, it has been believed that there are two important themes to consider. First, race/ethnicity is sometimes used to reflect social class when it is more accurately a proxy of social class in the U.S. due to confounding variables associated with racial/ethnic membership. Second, that while the social gradient operates across all racial/ethnic groups, it may manifest differently across subgroups. This is likely due to the intersection of race and social class, lending to sometimes synergistic effects on health outcomes. Both themes are discussed below.

Race/ethnicity is highly associated with SES in the U.S., and it is difficult to disentangle the effects of one from the other29, 30, 36 as racial/ethnic minorities are disproportionately represented in lower levels of SES. Research on racial inequities in the U.S. repeatedly demonstrates that Blacks and American Indians experience the worst health profiles while Whites, in general, experience the best health profiles.31, 37 These patterns also exist in global trends in which infectious and chronic diseases disproportionately burden racial minority members who endure the highest levels of discrimination, oppression, and marginalization.30, 38, 39, 40 These racial/ethnic differences most likely do not reflect genetic or inherent traits that lead to poor outcomes. Rather, for racial/ethnic minority members, poverty interacts with racial segregation, leading to negative downstream consequences from poorer education, decreased employment opportunity, poorer built environments, less access to quality food markets, decreased social networks, and increased neighborhood violence.41, 42, 43, 44 Race and ethnicity are often used as proxies for social class in the epidemiological literature,32, 33 illustrating how economic, social, and political power can be distributed among different dimensions.³⁵

While the social gradient phenomenon operates across race and ethnicity, its effects, directionality, and linear trends are not uniform. The social gradient may operate more strongly for some racial/ethnic groups as demonstrated by a study by Krieger and colleagues³⁵ that examined the role of the social gradient among different racial/ethnic groups across five major cancer sites: breast, cervix, colon, lung, and prostate. Findings demonstrated differential impact of the social gradient (in both magnitude and direction) among racial/ethnic groups and across cancer sites. Compared to all other racial/ethnic groups, the social gradient was strongest for White women with regard to cervical cancer incidence. With regard to colon and lung cancer, poorer Black and White respondents had higher incidence rates while higher incidence was found among the affluent Hispanics, demonstrating that reverse effects of social class can be found across race/ethnicity. The social gradient may also manifest in linear and non-linear patterns. Braveman and colleagues⁴⁵ examined socioeconomic disparities across multiple health indicators in the U.S., detailing the social gradient in health among White, Black, and Hispanic groups. While the study indicated linear trends of the social gradient for Whites and Blacks, the trend was less consistent for Hispanics. It is likely that the social gradient may not act in a linear fashion for some racial/ethnic minority groups due to the coinciding effects of acculturation.

The social gradient may act in curvilinear fashion for some racial/ethnic groups such as Hispanics and Asians as it relates to acculturative processes that occur within immigrant populations. Research shows that first generation immigrants display better health status than second generation immigrants; a phenomenon referred to as the immigration or acculturation paradox.46, 47

As these racial/ethnic immigrant groups make gains in social class, they likely have increased exposure to the dominant culture and adopt associated attitudes and behaviors. This initial integration of mainstream values and behaviors through acculturation is associated with increased risky behaviors, including smoking, alcohol use, sedentary lifestyles, and poorer diet.48, 49, 50, 51 It has been hypothesized that beyond a certain point, further gains in social class may afford these racial/ethnic immigrant groups protective effects associated with higher SES such as decreased demarginalization, and as a result, lead to a return to healthier profiles. In order to ascertain the role of acculturation and elucidate the effects of race/ethnicity and the social gradient on health, the present study will analyze factors contributing to health behaviors and outcomes while controlling for acculturation.

The present study offers new and significant contributions to the literature by examining how the social gradient phenomenon may manifest differently across different racial/ethnic groups. This study relies on data from the California Health Interview Survey (CHIS), a large cohort, state-representative sample with significant proportion of respondents from diverse racial/ethnic groups, particularly Asians and American Indians, groups that have been under examined in social gradient literature to date.35, 45 The study has three main objectives:

• To examine the health profiles among the different racial/ethnic groups. Univariate analyses will demonstrate that Whites have the most favorable health profiles in comparison to all other racial groups (when not controlling for effects of the social gradient).

• To assess the role of the social gradient on health outcomes and behaviors. It has been predicted that increasing levels of education and family income will be associated with positive health behaviors (i.e., smoking, drinking, physical activity, and diet) and health status (i.e., with limited activity due to chronic condition, blood pressure, obesity, diabetes, BMI, and perceived health condition).

• To examine differential effects of the social gradient in health among different racial/ethnic groups. More linear gradient effects have been predicted among Whites and Blacks but more non-linear gradient effects among Hispanics and Asians while controlling for important covariates including acculturation.