Life Expectancy

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Life Expectancy

EXPLANATIONS FOR RACIAL INEQUALITIES IN LIFE EXPECTANCY

Race is widely understood as a sociocultural phenomenon, not a biological one. This view is based on evidence that conventional racial categories fail to capture global patterns of human genetic variation. Yet severing the link between race and human biological variation may create an unintended blind spot: Race is biological in the sense that racial differences in life experiences are linked to biological outcomes, including death and disease. Historically, these health inequalities were interpreted as evidence of innate biological differences between racially defined groups. But researchers increasingly seek to understand them as the biological consequences of social inequalities among racialized groups.

Racial inequalities in health are often summarized by reference to life expectancy, a standard indicator of population health. This entry first defines life expectancy and then presents evidence for current and historical racial inequalities in life expectancy in the United States. It then reviews explanations for the persistent gap in life expectancy and identifies key needs for research to improve our understanding of racial inequalities in health.

RACIAL INEQUALITIES IN LIFE EXPECTANCY

Life expectancy is calculated on the basis of age-specific death rates for a population at a given point in time. It estimates the average number of years people who have reached a particular age would continue to live, if current death rates at each age remained constant over time. Because death rates do not remain constant, life expectancy does not measure the longevity of actual birth cohorts. Rather, it summarizes the overall mortality profile of a population at a particular point in time.

Life expectancy can be calculated for any age, but the most common summary of a population’s health status is life expectancy at birth. However, this measure is heavily influenced by rates of infant and child mortality, especially if these rates are high. When researchers wish to exclude the impact of early mortality on population health, they typically calculate life expectancy at ages five or fifteen.

Black and White Americans. In the United States, research on racial inequalities in life expectancy focuses largely on inequalities between black and white Americans.

Figure 1 shows how these inequalities persisted over the twentieth century. At the beginning of the century, the black-white gap in life expectancy at birth was 14.6 years. This gap reached a peak in 1903 (17.8 years) and declined through World War II. (It narrowed considerably but temporarily during the “colorblind” 1918 flu pandemic.) By 1955, the black-white gap in life expectancy had fallen to less than seven years.

However, during the second half of the century, racial inequalities in life expectancy scarcely changed, despite substantial gains in life expectancy for the population as a whole (Figure 1). Indeed, in 1995 the black-white gap in life expectancy was the same as it was in 1956 (6.9 years). Only in the last few years has this gap narrowed again, reaching a historic low of 5.3 years in 2003.

The apparent stability of this inequality masks the diverging fortunes of black men and women, as Figure 1 shows. From 1950 to 2003, the gap in life expectancy between black and white women fell from 9.3 to 4.4 years, such that black women’s life expectancy at birth now exceeds that of white men. During the same period, the gap between black and white men climbed to a peak of 8.5 in 1982, before falling again to 6.3 years in 2003. This gap between black and white men is still greater than it was in 1955.

The historical depth of inequalities between black and white Americans explains the usual focus on black-white comparisons of health and life expectancy. But these comparisons are limited in at least three ways. First, crude black-white comparisons neglect the diversity of health and mortality profiles within racial categories. Second, they ignore the changing racial demography of the United States in the wake of increasing immigration from Asia and Latin America since the 1960s. Third, they imply that race per se is the most important determinant of health disparities, rather than identifying the specific causal influences on racial inequalities of health.

“Eight Americas.” One group of researchers addressed these concerns by dividing the U.S. population into eight distinct groups based on race and the socioeconomic attributes of counties where people lived (Murray et al. 2006). The resulting “Eight Americas,” shown in Table 1, capture the striking range of inequalities in life expectancy in the United States.

*Table 1.*
Life Expectancy and Socioeconomic Inequalities across “Eight Americas”
America	Description	Population (millions)	Average income per capita	Percent completing high school	Male life expectancy at birth	Female life expectancy at birth
SOURCE : Reprinted from Murray et al. (2006). “Eight Americas: Investigating mortality disparities across races, counties, and race-counties in the United States.” PLoS Medicine 3: e260.
1	Asian	10.4	$21,566	80	82.8	87.7
2	Northland lowincome rural white	3.6	$17,758	83	76.2	81.8
3	Middle America	214.0	$24,640	84	75.2	80.2
4	Low-income whites in Appalachia and the Mississippi Valley	16.6	$16,390	72	71.8	77.8
5	Western Native American	1.0	$10,029	69	69.4	75.9
6	Black Middle America	23.4	$15,412	75	69.6	75.9
7	Southern lowincome rural black	5.8	$10,463	61	67.7	74.6
8	High-risk urban black	7.5	$14,800	72	66.7	74.9

Relative to global inequalities in life expectancy, racial disparities within the United States are massive. The gap between Americans with the longest and shortest life expectancies—Asian-American women and black men in high-risk urban settings—is an astonishing 21 years, more than the difference between Japan and Bangladesh, for example. Within sexes, the gap between the longest and shortest life expectancies is 13.1 years for women and 16.1 years for men. These gaps are 2.6 to 3 times greater than the inequalities between black and white women in the United States as a whole. They also rival the nearly 14-year gap in life expectancy between high-income OECD (Organisation for Economic CoOperation and Development) countries and low-income developing countries (United Nations Development Programme 2005). Indeed, the life expectancy of high-risk urban black men in the United States is more typical of life expectancy in developing countries than it is of high-income countries like the United States (Figure 2).

Table 1 also highlights diversity within conventional racial categories. Murray and colleagues identify three black and three white Americas. Across the white Americas, the gap in life expectancy is 4.0 years for women and 4.4 years for men. Across the black Americas, the gaps are smaller but still substantial—1.3 years for women and 2.9 years for men. These gaps cannot be attributed simply to socioeconomic inequalities. Despite low per capita income, rural whites in the northern plains and Dakotas have a significant mortality advantage over high-income whites in America. Likewise, despite greater poverty, rural black men in the South have a slight edge in longevity over black men in high-risk urban environments.

Murray and colleagues emphasize that inequalities in life expectancy across the eight Americas are not the result of differential mortality among children or the elderly. Although racial inequalities in infant mortality persist, the largest mortality differences are among young (ages 15–44) and middle-aged (ages 45–64) adults. These differences are the result primarily of noncommunicable causes such as cardiovascular disease, diabetes mellitus, cancer, and liver cirrhosis. Injuries and HIV/AIDS also contribute significantly to excessive mortality among young adults. In separate analyses, Wong and colleagues (2002) estimate that eliminating hypertension, or chronic high blood pressure, would have the largest impact on reducing racial differences in life expectancy, followed by HIV,

homicide, diabetes, colon cancer, pneumonia, and ischemic heart disease.

EXPLANATIONS FOR RACIAL INEQUALITIES IN LIFE EXPECTANCY

There remains debate about why these inequalities exist. Many critics note that the debate often ends prematurely with the assumption that race is biology and that racial differences in health are largely determined by genetic differences. However, in the last twenty years, clinicians and health researchers have become increasingly aware of the problems with race as a biological construct, and there is growing emphasis on the social and cultural factors that shape racial inequalities in health.

In a recent review, Dressler, Oths, and Gravlee (2005) identify five models for explaining racial inequalities in health:

A racial-genetic model
A socioeconomic model
A health-behavior model
A psychosocial stress model
A structural-constructivist model.

Although the review focuses largely on infant mortality and high blood pressure, the five models apply to explanations for racial health inequalities in general.

The racial-genetic model holds that racial inequalities in health are primarily genetic in origin. This view has a long history in American medicine (Krieger 1987). Indeed, many key figures in the history of scientific racism were physicians and medical scientists who asserted the natural biological inferiority of blacks as the basis of their greater susceptibility to disease and premature death. For example, during the first years of Reconstruction, as many as one-quarter to one-third of former slaves may have died in parts of the southern United States. Many white physicians interpreted this trend as evidence of African Americans” innate biological inferiority, not of fundamental social inequality.

The basic assumptions of this period remain surprisingly common today. Whereas social scientists generally take it for granted that race does not correspond to meaningful genetic differences, many physicians and biomedical researchers still assume that there are innate racial differences in the susceptibility to disease. Some prominent researchers explicitly defend race as a useful framework for identifying the genetic basis of common diseases (Risch et al. 2002). Yet there remains little reason to think that genes are to blame for racial inequalities in life expectancy (Goodman 2000).

Most research on the nongenetic basis of racial inequalities in health has focused on the role of socioeconomic status (SES), usually defined as some combination of education, occupation, and income. The rationale is that race and SES are confounded, such that controlling for differences in SES should either eliminate racial disparities in health or reveal the true causal effect of race. As a rule, accounting for SES reduces but does not eliminate racial inequalities in health. This pattern also holds for life expectancy, as the Eight Americas study suggests (Table 1).

Some researchers have interpreted the residual relationship between race and health, after controlling for SES, as support for the racial-genetic model. But this interpretation is untenable because race cannot be reduced to class; racial inequality affects health through mechanisms other than socioeconomic deprivation. Thus, controlling for SES, even when it is measured well, does not eliminate differences between racially defined groups in noneconomic factors that influence population health (Kaufman, Cooper, and McGee 1997).

The health behavior model is in part a response to the limitations of the socioeconomic model. One possible reason that SES does not account for racial inequalities in health is that it does not capture the unequal distribution of health-related behaviors across racially defined groups. The health behaviors most often discussed include dietary intake and physical activity (resulting in excessive weight and obesity), alcohol consumption, and smoking. These factors clearly impact health and longevity. However, there is little evidence that they account for the relationship between race and health (Dressler, Oths, and Gravlee 2005).

The incomplete success of socioeconomic and health-behavior models has stimulated research on the contribution of psychosocial stress to racial inequalities in health. Research in this tradition begins from the premise that institutional and interpersonal racism create stressful life circumstances that adversely impact the health of racially oppressed people. The literature in this area is enormous and growing. Dressler and colleagues (2005) distinguish three streams of research on psychosocial stress, including (1) studies that measure general markers of stress exposure such as depression and anxiety, (2) studies that assess the perceived experience of discrimination, and (3) studies that adapt general models of the stress process to the unique stressors and coping resources in African-American communities.

Each approach has produced novel insights, confirming the importance of psychosocial stress in the origin of racial inequalities in health. Yet much research in this tradition remains vulnerable to the limitations of stress research in general. First, many stressors, including exposure to racism, are difficult to measure apart from individuals” efforts to cope with those stressors. Second, research on psychosocial stress traditionally focuses on individual experience, with too little consideration of how stressors and coping resources are socially distributed and culturally constructed.

The structural-constructivist model addresses these limitations. This approach seeks to explain racial inequalities in health at the intersection of social structure and cultural meaning. For example, Dressler (2005) shows that racial inequalities in mental and physical health are associated with one’s ability to obtain culturally valued resources, which is partly constrained by structural inequalities. Gravlee, Dressler, and Bernard (2005) show that the association between skin color and blood pressure in Puerto Rico is shaped both by the meaning people attribute to skin color and by access to socioeconomic resources. These examples illustrate the promise of research that examines how social structural forces condition exposure to culturally defined stressors and coping resources.

RESEARCH NEEDS

Racial inequalities in life expectancy pose three critical challenges for the social and biomedical sciences. First, given the persistence of racial-genetic determinism, it remains necessary to clarify the fallacy of race as a framework for understanding human biodiversity. Second, there is a need for research on how hidden assumptions about race shape biomedical research and clinical practice and how clinical practice and biomedical research, in turn, perpetuate prior beliefs about race. Third, researchers need to integrate multiple levels of analysis—sociocultural, environmental, behavioral, physiological, molecular—to understand how the sociocultural phenomena of race and racism become embodied in biological outcomes over the life course.

BIBLIOGRAPHY

Arias, Elizabeth. 2006. United States Life Tables, 2003. National Vital Statistics Reports Vol. 54, No. 14. Available from http://0-www.cdc.gov.mill1.sjlibrary.org/nchs/data/statab/lewk3_2003.pdf.

Dressler, William W. 2005. “What’s Cultural about Biocultural Research?” Ethos 33 (1): 20–45.

———, Kathryn S. Oths, and Clarence C. Gravlee. 2005. “Race and Ethnicity in Public Health Research: Models to Explain Health Disparities.” Annual Review of Anthropology 34 (1): 231–252.

Goodman, Alan H. 2000. “Why Genes Don’t Count (for Racial Differences in Health).” American Journal of Public Health 90 (11): 1699–1702.

Gravlee, Clarence C., William W. Dressler, and H. Russell Bernard. 2005. “Skin Color, Social Classification, and Blood Pressure in Southeastern Puerto Rico.” American Journal of Public Health 95 (12): 2191–2197.

Kaufman, Jay S., Richard S. Cooper, and Daniel L. McGee. 1997. “Socioeconomic Status and Health in Blacks and Whites: The Problem of Residual Confounding and the Resiliency of Race.” Epidemiology 8 (6): 621–628.

Krieger, Nancy. 1987. “Shades of Difference: Theoretical Underpinnings of the Medical Controversy on Black/White Differences in the United States, 1830–1870.” International Journal of Health Services 17 (2): 259–278.

Murray, Christopher J. L., C. Sandeep, Catherine Michaud Kulkarni, et al. 2006. “Eight Americas: Investigating Mortality Disparities Across Races, Counties, and Race-Counties in the United States.” PLoS Medicine 3 (9): e260.

National Center for Health Statistics. 2005. Health, United States, 2005. Hyattsville, MD: National Center for Health Statistics. Available from http://www.cdc.gov/nchs/hus.htm.

Risch, Neil, Esteban Burchard, Elad Ziv, and Hua Tang. 2002. “Categorization of Humans in Biomedical Research: Genes, Race and Disease.” Genome Biology 3: comment2007. 1–comment2007.12.

United Nations Development Programme. 2005. Human Development Report 2005. New York: United Nations Development Programme.

Wong, M. D., M. F. Shapiro, W. J. Boscardin, and S. L. Ettner. 2002. “Contribution of Major Diseases to Disparities in Mortality.” New England Journal of Medicine 347 (20): 1585-1592.

Clarence C. Gravlee

Encyclopedia of Race and Racism