Measurement issues in health disparities research

Health Services Research, Oct, 2005 by Mildred Ramirez, Marvella E. Ford, Anita L. Stewart, Jeanne A. Teresi

The proportion of both minority and older adults in the United States is growing; as a result, the older population is becoming more racially and ethnically diverse (Ford and Hatchett 2001; Sinclair et al. 2002; Federal Interagency Forum on Aging-Related Statistics 2004). Members of minority groups have higher rates of morbidity and mortality than do their counterparts in the general population for almost all categories of disease (Sinclair et al. 2002; Federal Interagency Forum on Aging-Related Statistics 2004; Frist 2005). Racial and ethnic disparities in health and health care have been well documented, and the elimination of such disparities is currently a part of a national agenda (Fiscella et al. 2000; Ashton et al. 2003). It is, therefore, not surprising that such racial and ethnic disparities in health are also reflected within the U.S. veteran population (Young, Maynard, and Boyko 2003; Zingmond et al. 2003), a focus of this special issue. Thus, addressing measurement issues in the assessment of the health status of diverse populations of older adults is of critical importance. Measurement accuracy (or inaccuracy) can affect study results producing, for example, biased estimates of symptoms and disorder, and the generation of misleading conclusions. This article provides a brief overview of the issues regarding measurement in diverse populations.

The physical health challenges facing older racial and ethnic minority group members are numerous. Data show, for instance, that older African Americans, compared with older whites, have a higher incidence of hypertension, heart disease, stroke, and end-stage renal disease (Kotchen et al. 1998; Sinclair et al. 2002). In fact, the prevalence of hypertension is 50 percent higher in African American than in white adults (Kotchen et al. 1998). Additionally, African American men have both the highest incidence of and associated mortality from prostate cancer than any other racial or ethnic group, and this disparity continues to increase (Guo et al. 2000; Powell et al. 2000). Older Latinos, like older African-American adults, appear to have worse physical health than do older white adults (Villa and Aranda 2000; American Heart Association National Center 2005; National Institute of Diabetes and Digestive and Kidney Diseases 2005). Latinos are 1.9 times more likely to have diabetes than are whites of similar age; 25-30 percent of Latinos age 50 years or older have either diagnosed or undiagnosed diabetes (National Institute of Diabetes and Digestive and Kidney Diseases 2005). Additionally, Latinos, like African Americans, appear to be at particular risk for cardiovascular disease and stroke, which account for 31 percent of all Latino deaths annually (American Heart Association National Center 2005). Asian American women, in particular, appear to be at greater risk for breast cancer than are other women; breast cancer is the most common cause of cancer incidence and mortality among members of this group (Kagawa-Singer and Pourat 2000; Tanjasiri and Sablan-Santos 2001).

Some studies have shown that health-related disparities among racial and ethnic groups disappear or are attenuated once confounding demographic variables such as income and education have been controlled (de Rekeneire et al. 2003; Bromberger et al. 2004). However, a greater number of studies demonstrate that racial and ethnic disparities remain even when such adjustments have been implemented (see Mayberry, Mili, and Ofili 2000; Kressin and Petersen 2001). Racial and ethnic disparities continue to be observed in epidemiological research, as reflected in different levels of risk factors, dissimilar rates of disease, differing responses to treatment, and unequal quality and access to care (Schneider, Zaslavsky, and Epstein 2002; Smedly, Stith, and Nelson 2002).

Racial and ethnic disparities in mortality rates may be because of comorbidity, access to health services, knowledge, attitudes and beliefs about disease, and/or disease biology (Ford and Hatchett 2001; Kaplan and Bennett 2003; Sankar et al. 2004). Longitudinal studies identifying other factors associated with disparities are needed because causal relationships involving health disparities and demographic factors cannot be determined from cross-sectional analyses, such as those presented in many of the studies cited above. However, a prerequisite to the alleviation of health disparities among racially diverse populations is addressing possible measurement bias in the assessment of self-reported health status. That is, in order for cross-cultural research to be conducted in a meaningful manner, it is important to determine first whether measures developed among nonminority populations perform in the same way when applied to minority populations.

Each racial and ethnic group has unique cultural characteristics including values, norms, and attitudes (Mutran, Reed, and Sudha 2001; Napoles-Springer and Stewart 2001; Shire 2002; Cabassa 2003). Hence, it is imperative to consider, for each of these groups, whether existing measures are relevant, appropriate, reliable, and valid. Although the importance of the cultural validity of questionnaire items has been recognized by many researchers (Angel and Frisco 2001; Mui, Burnette, and Chen 2001; Napoles-Springer and Stewart 2001), the practice of applying standard measures to groups of racial and ethnic minorities (Robin et al. 2003; Stanley and Chang 2003), and to groups with lower socioeconomic status without investigation of the psychometric properties for these populations remains common.