Ethnic health disparities in arthritis and musculoskeletal diseases: Report of a scientific conference


The National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) at the National Institutes of Health (NIH) is committed to better understanding, diagnosis, treatment, and prevention of diseases of the skin, muscles, bones, and joints. Many of these diseases affect women and minority populations disproportionately, both in increased numbers of people affected as well as increased severity of disease. The NIAMS interests are focused on advancing medical research to identify and address the underlying causes of health disparities in minority populations.

In December 2000, NIAMS joined with a number of other NIH components, the Office of Research on Minority Health, Office of Research on Women's Health, Office of Disease Prevention, and the Office of Behavior and Social Sciences Research, and with the Centers for Disease Control and Prevention, the Arthritis Foundation, the American College of Rheumatology, the American Academy of Orthopaedic Surgeons, and the American Academy of Dermatology in sponsoring a scientific conference to address the many aspects of health disparities within our mission areas. The conference also served to identify scientific opportunities and knowledge gaps that need to be filled in order to eliminate these health disparities. The following article summarizes some of the conference highlights relating to arthritis and musculoskeletal diseases. Stephen I. Katz, MD, PhD Director National Institute of Arthritis and Musculoskeletal and Skin Diseases Bethesda, MD

Stephen I. Katz, MD, PhD, Director, National Institute of Arthritis and Musculoskeletal and Skin Diseases, Bethesda, MD


Arthritis and musculoskeletal conditions are among the most common health problems in the US, with 43 million adults currently affected and a projected 60 million adults to be affected by 2020 (1). Marked differences in the incidence, severity, processes of care, and outcome in a number of arthritis and musculoskeletal conditions exist among different racial or ethnic groups (2–10). The reasons for these disparities are largely unknown and span the gamut of possibilities, from genetic predisposition to environmental exposures to behavioral and social etiologies. While recognizing that the gap is multifactorial, incompletely understood, and potentially difficult to redress in its entirety, a number of public and private initiatives have been mounted to address these issues. For example, a new National Center on Minority Health and Health Disparities has been established at the National Institutes of Health (NIH). Healthy People 2010 (11), which has set the nation's health objectives for the beginning of the 21st century, has included goals to eliminate health disparities and improve the quality and years of healthy life. For the first time, arthritis and musculoskeletal conditions have been identified as distinct and important public health concerns.

This article summarizes a conference—the first of its kind—organized and hosted in December 2000 by the National Institute of Arthritis and Musculoskeletal and Skin Diseases and cosponsored by the Centers for Disease Control and Prevention, the Arthritis Foundation, the NIH Office of Research on Minority Health, the NIH Office of Research on Women's Health, the NIH Office of Disease Prevention, the NIH Office of Behavioral and Social Sciences Research, the American College of Rheumatology, the American Academy of Orthopaedic Surgeons, and the American Academy of Dermatology. The aim of the conference was to address ethnic disparities in arthritis, musculoskeletal, and skin diseases. Almost half of the diverse group of conferees were people of color. A summary of the disparities in skin diseases has been reported elsewhere (12).

The objectives of the conference were as follows: 1) to highlight current knowledge about genetic, environmental, social, and behavioral factors related to ethnic differences in prevalence of, and morbidity and disability from arthritis, musculoskeletal, and skin conditions; 2) to identify strategies to reduce disparities and barriers to dissemination of these strategies; and 3) to identify research needs and opportunities in these areas.

Measuring and interpreting observed disparities in the prevalence and severity of disease and health outcome

Before we can examine racial and ethnic disparities in arthritis and musculoskeletal conditions, we must acknowledge and attempt to address basic methodologic difficulties surrounding the measurement and interpretation of relevant variables. These variables include definitions of race and ethnicity, disease criteria, and potential confounders, such as socioeconomic status (SES).

First, race and ethnicity are inherently difficult concepts. Definitions of racial and ethnic groups may vary by context, with different meanings ascribed according to distinct purposes of clinical practice, medical research, social science research, and even national surveillance of vital and health statistics. Definitions of race and ethnic groups have also varied from census to census and from study to study. While race and ethnicity are terms that are frequently used interchangeably, they represent related but distinct constructs. The view of race as a biologic concept is grounded on largely discredited notions of phenotypic, genetic, and biologic characteristics that were believed to sort humans into genetically and biologically homogeneous groups. Instead, race has often been used as a social construct, which has varied over time and according to the context in which it was used. In contrast, ethnicity is an accepted social construct that defines groups according to common language, national origin, customs, and culture, and it is rarely fully characterized in medical and epidemiologic research (13).

Race and ethnicity are obviously intertwined and may be measured by different methods. For most research purposes, race and ethnicity are now thought to be best measured by self-identification. The discourse surrounding the recent changes in the federal guidelines for the census concerning self-identified data about race and ethnicity, which now allow citizens to identify themselves as being of multiple races, highlights the continuing challenges of measuring these concepts. As the US population becomes increasingly diverse, the concepts of race and ethnicity will undoubtedly change further, perhaps rendering current definitions less meaningful.

Second, for much of the work on disparities, standardized case definitions for disease and/or outcomes may not exist or are not uniformly applied, making comparisons between subjects and across studies perilous. For instance, cases identified from population-based sources and administrative databases may not utilize disease classification criteria; however, these sources of data are frequently the only feasible, affordable ones of sufficient size on which to base inferences.

Given these realities, one must first be reassured that alleged ethnic disparities in disease or health outcome are not the result of bias, confounding, or chance. For example, in the US, African American ethnicity is associated overall with indicators of lower SES, which is itself a risk factor for poor health outcome. Teasing out the effects of SES from genetic and environmental factors when explaining increased morbidity and mortality observed in African Americans can be difficult. SES has been variously defined by years of education, income, employment status, occupational prestige, health insurance source, postal code, or a combination of these factors. Some of these are more likely the result of the disease or condition in question than risk factors for disparities that precede the onset of disease. In addition, while SES may confound a potentially true relationship between ethnicity and disease, associations between ethnicity and disease or outcome can also vary by SES. That is, an association between ethnicity and disease may only be evident in certain SES groups, as is seen with radiographic hip osteoarthritis (OA) in the Johnston County Osteoarthritis Project discussed below.

Thus, SES should be evaluated as not only an independent risk factor and potential confounder in studies of ethnicity, disease, and outcome, but also a potential interacting variable or effect modifier. Even so, exposing SES as the factor responsible for a given ethnic association with disease or outcome does little to identify actionable interventions, since SES may itself be a proxy for environmental exposures or lifestyle factors that may influence disease or outcome.

Genetic, environmental, social, and behavioral factors in ethnic disparities in the prevalence and severity of disease

In rheumatology, ethnic differences in disease susceptibility and outcome have been extensively studied in systemic lupus erythematosus (SLE) (2, 3, 14–18). African Americans have a higher prevalence of SLE, more severe disease, and a worse outcome compared with Caucasians (2, 16, 17). Hispanics may also be at increased risk of poor outcome from SLE (3, 16, 17). Genetic factors have long been considered major determinants of disease in SLE, and variations in such factors may explain some of the differences in lupus manifestations and outcome among ethnic groups (16, 17). Similarly, genetic differences have also been advanced as a potential explanation of ethnic differences in the manifestations of systemic sclerosis in Choctaw Indians compared with other ethnic groups (4). Recognition of the relative importance of inherited factors, including HLA and receptors for immunoglobulins, among various ethnic groups may provide insights into the clinical differences noted in ethnic groups and may enhance our understanding of the mechanism of disease.

While the importance of genetics in ethnic differences in SLE and other systemic autoimmune diseases cannot be denied, these factors do not explain all of the ethnic disparities observed in these diseases, nor are they modifiable at the present time. Attention is also being increasingly focused on the identification of potentially modifiable environmental and social/behavioral factors underlying ethnic disparities in disease manifestations and outcome. Further, the interaction of genetic factors with environmental and social/behavioral factors is also receiving recognition as an important avenue for research. For example, SLE has been associated with exposure to multiple drugs (19), the outbreak of eosinophilia–myalgia syndrome was caused by the ingestion of contaminated L-tryptophan (20, 21), and a disease resembling systemic sclerosis was induced by the ingestion of contaminated rapeseed oil (21). Similarly, animal models of lupus have also shown the influence of environmental factors, such as pristane, in modifying the disease in genetically susceptible mice (22).

Given the complex relationships among these factors, studies of disparities must deal with a broad and comprehensive spectrum of data, including genetics, SES, environmental exposures, and social and behavioral factors. The first such study to do this in SLE focused on modifiable nutritional, behavioral, and psychosocial factors in a 5-center study of Caucasians and African Americans balanced for SES and race (18, 23). Other examples include the LUMINA (lupus in minority populations, nature versus nurture) study, which examined genetic, environmental, and social/behavioral factors in SLE in Caucasians, African Americans, and Hispanics in the southeastern US (16, 17), and the Carolina Lupus Study, which focused on environmental, reproductive, and genetic factors in SLE in African American and Caucasian women in North Carolina and South Carolina. The Carolina Lupus Study found similar risk factors for disease in both ethnic groups and a possibly protective effect of breastfeeding as a potentially modifiable risk factor that could explain some ethnic differences in SLE (24). Importantly, these studies have demonstrated the significance of examining ethnic differences in disease manifestations and outcome utilizing uniform selection criteria and methodologies across ethnic groups within the same study.

Ethnic disparities also exist in the prevalence and severity of other non-autoimmune musculoskeletal conditions, such as OA. African American women may be 2–3 times as likely as Caucasian women to have radiographic OA of the knee, and it has recently been shown that African American women also have a higher prevalence of radiographic knee OA than do Mexican American women (5, 6, 25, 26). In the Johnston County Osteoarthritis Project, a population-based study of OA in a rural North Carolina county, more severe and bilateral radiographic knee OA was documented both in African American women and in African American men, as compared with Caucasians (27, 28). In addition, African American men were more likely than Caucasian men to have both radiographic hip OA and bilateral hip OA, a result found only in those in the lower SES group. African American men who had fewer than 12 years of formal education were ∼65% more likely to have radiographic hip OA and twice as likely to have bilateral radiographic hip OA compared with Caucasian men who had similar educational attainment. This emphasizes the importance not only of controlling for SES, but also of examining the interaction between ethnic group and SES in outcomes.

The Johnston County Osteoarthritis Project has also shown possible ethnic differences in factors associated with serum biomarkers of OA (29, 30). Comparable, comprehensive, population-based data on OA in other ethnic groups in the US are generally lacking, although data on radiographic knee OA in older Mexican American participants of the Third National Health and Nutrition Examination Survey have recently been released (26). As in studies of systemic autoimmune diseases, these studies in OA demonstrate the importance of assessing genetic, environmental, and social/behavioral data and their interactions.

Ethnic differences in access to care, care-seeking, and utilization of care

The study of ethnic differences in access to, utilization of, and quality of health care sources for arthritis and musculoskeletal conditions is in its infancy, but to judge from findings in other diseases, it would be a fertile area for future work. The few studies done in this area have analyzed data from national Medicare and medical expenditure data sets, with the difficulties inherent in secondary data analysis regarding validation of diagnoses, missing data, and definitions of relevant variables. African Americans, Hispanics, and Asians appear to be 3–25 times less likely than Caucasians to undergo total joint replacement for OA of the hip and are also less likely to have primary OA as the reason for the hip replacement (9, 31, 32). Further studies of possible reasons behind such disparities, such as ethnic differences in the prevalence of disease, access to care, insurance coverage, care preferences, and quality of care received, are needed.

Again, studies attempting to sort out the relative importance of each of these issues must include comprehensive assessment of SES, medical insurance status, availability of and access to care, and other psychosocial factors likely to be associated with outcomes. One study of total joint replacement for knee or hip OA in African American and Caucasian male veterans (with presumed equality of at least some factors related to health care quality and access) found significant ethnic differences in their awareness and understanding of total joint replacement, as well as in their perceptions of the risks and benefits thereof (10). Another study of low back pain in African Americans and Caucasians (33) found ethnic differences in care-seeking, with African Americans being less likely to seek medical care but more likely to receive a less intensive diagnostic evaluation and therapeutic course.

Differences in the use of self-care, alternative and complementary care, and traditional medical care for arthritis and musculoskeletal conditions have also been observed (7, 34, 35). African Americans and Hispanics are more likely to use prayer, herbs, ointments, and rubs and less likely to use traditional medical care for arthritis symptoms than are Caucasians (7, 34, 35). Studies examining knowledge, beliefs, and psychological factors as explanations for differences in self-care, care-seeking, and receipt of care in different populations are needed (35, 36).

Attention has also recently focused on characteristics of the health care provider and the doctor–patient interaction to learn more about ethnic differences in the care that is recommended and delivered for certain conditions (37). Some of these studies may require the use of qualitative methods in their attempt to unveil the reasons behind the observed disparities.

Strategies for eliminating disparities and barriers to the dissemination of such strategies

The elimination of ethnic disparities in outcomes will undoubtedly require a multipronged approach aimed at the root cause or causes. Attention to factors that are operative across a variety of conditions will have the largest impact on the health of the population and the broadest support for social initiatives. Remediation of some of the factors potentially related to ethnic disparities in outcome, such as limited access to quality care, medications, and surgery, will undoubtedly require interventions at the societal and political levels. Several other potentially important basic factors may be amenable to investigation and/or intervention at the individual level. These include self-efficacy, literacy, and racial stereotyping.

Self-efficacy is the psychological trait whereby individuals have (or develop) competence in their ability to monitor and manage their condition (38). Increasing self-efficacy improves health outcomes across a host of conditions (39, 40). The Arthritis Self-Help Program is an intervention that empowers patients, improves their self-efficacy, improves health across a number of rheumatic conditions and numerous ethnic groups, and is cost-effective (39–41). Despite this, the program is used by only a small proportion of the people with arthritis and musculoskeletal conditions who could potentially benefit (42). Identification of human, social, and practical barriers to the dissemination of this and other known and effective programs will be critical to helping to redress disparities. Research needs to be directed toward discovering other “basic mechanisms” and evaluating efficacious strategies for modifying these factors.

The conference showcased examples of successful programs targeted at ethnic populations with arthritis and musculoskeletal disorders in New York, Detroit, and Los Angeles. Speakers reported the common challenges of erratic funding, which is frequently insufficient, lack of appropriate ethnic leadership and health professionals, and provision of health care to populations weakened by social deprivation, lack of supports, and racial stereotyping. Despite this, these programs prevailed. Some of the features that were identified as being invaluable to the programs included the following: 1) respectful, meaningful, and culturally sensitive interactions based on a community model; 2) multiple partnerships involving community institutions (e.g., African American churches), academia, state public health departments, etc.; and 3) dedicated leaders.

Another issue identified as being important, underrecognized, and understudied in redressing disparities was literacy. Functional literacy—not simply the ability to read—is impaired sufficiently to affect everyday life in 47–51% of Americans; it is associated with inferior health outcomes and increased health care costs and is amenable to clinical and public health strategies (43). There is only one NIH-funded study of functional literacy in arthritis and musculoskeletal conditions.

Finally, the potential role of racial bias, which is neither defined nor addressed in classic epidemiology, in health disparities led to an emotional discussion. The conferees disagreed about the importance of racial bias in explaining health disparities and impeding the dissemination of strategies to eliminate them. However, racial/ethnic stereotyping, regardless of whether it is negative or positive, was acknowledged as being ever-present, both in dominant and in nondominant ethnic groups.

Research agenda for the study and elimination of ethnic disparities

Having recognized multiple knowledge gaps concerning the presence and causes of disparities and the means of eliminating them, the conference participants then identified the research opportunities. A research agenda was proposed and discussed according to the above outline regarding measurement issues, the influence of social, genetic, behavioral, and environmental issues in disparities, and strategies for eliminating disparities and barriers to the dissemination of such strategies.

Documentation of disparities and identification of etiologies for disparities.

For some conditions or ethnic groups, such as SLE in African Americans compared with that in Caucasians, disparities in the incidence and outcome are well established, while in other conditions or in other ethnic groups, basic epidemiologic or clinical data either have not been collected or have not been analyzed, and it is therefore not yet possible to establish whether disparities exist. For situations in which data on disparities are available, future research should go beyond describing the disparities to identifying the explanations for the disparities and to designing and evaluating interventions that would address potentially modifiable factors in order to eliminate those disparities.

For situations in which data about disparities are limited or nonexistent, such as OA in Hispanics, Asians, or Native Americans, more basic epidemiologic investigation is needed. Existing data sets, albeit with limitations, in which these groups have been sampled could be examined as a starting point. Further in-depth study into the etiology and explanations for disparities would almost certainly require the accumulation of more comprehensive data on cultural, environmental, social/behavioral, and genetic factors and the interaction of these factors with each other. Studies of migrants could illuminate potential interactions between genetics and environment. Further, it must be recognized that subgroups with different national origins, geographic locations in the US, degrees of acculturation, languages, and cultures may not be comparable with respect to some outcomes.

The mechanisms of genetic, environmental, social, and behavioral factors in disparities.

Research into the basic biology of genetic, environmental, social, and behavioral factors and their interactions related to particular conditions and outcomes is a major priority. This will, by necessity, involve multiple scientific disciplines, such as genetics, toxicology, immunology, epidemiology, and behavioral science, and should be both exploratory and hypothesis-driven in order to identify novel environmental exposures and to understand their interactions with the host and the basic mechanisms by which they perturb the immune and/or neuroendocrine systems. Genetic factors could be important in disease susceptibility, severity of illness, disease subsets, metabolism of and response to pharmaceutical or biologic agents, and/or psychobehavioral characteristics that affect treatment.

Confounding and effect modification by SES need to be addressed in the analysis and interpretation of any study of disparities. Potential explanations for disparities should not stop at SES, however, but should attempt to understand the factors related to SES at both the individual and the societal level that can be amenable to intervention.

Disparities in the evaluation and treatment of arthritis and musculoskeletal conditions.

Research into the factors responsible for ethnic differences in processes of care, such as the evaluation of arthritis and musculoskeletal conditions, the use of self-care, complementary and alternative care, and formal medical care, the patterns of care, and access to and use of therapies such as joint replacement, should examine individual and societal factors, including characteristics of the health care providers and the medical care delivery system, and their potential interactions with the individual. Identification of potentially modifiable factors associated with disparities should be emphasized. Approaches to redressing the responsible factors that can be generalized across conditions and/or across ethnic groups are most likely to have a public health impact and should receive special emphasis. Cultural barriers, patient preferences, and resources for implementing public health recommendations need to be identified. Finally, factors limiting full implementation of known and effective interventions should be identified, and strategies to overcome them should be tested.


Disparities in the incidence and outcome of some arthritis and musculoskeletal conditions have been noted in some ethnic groups, but it is not known whether the factors that are responsible for these disparities are broadly relevant across a spectrum of conditions or are unique to particular conditions. Future research needs to move beyond description and attempt to understand the mechanisms for the disparities, be they genetic, environmental, cultural, behavioral, societal, or a combination of factors. Interventions need to be tested for their efficacy, effectiveness, and cost-effectiveness in eliminating the gap. The challenge to move research and practice forward in the next decade is daunting, and the stakes are high. The recognition that a problem exists and the multiple research initiatives that have been launched give cause for optimism.