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SPECIAL COMMUNICATION

Socioeconomic Status in Health Research One Size Does Not Fit All

Paula A. Braveman, MD, MPH Problems with measuring socioeconomic status (SES)—frequently included Catherine Cubbin, PhD in clinical and public health studies as a control variable and less frequently Susan Egerter, PhD as the variable(s) of main interest—could affect research findings and con- Sekai Chideya, MD, MPH clusions, with implications for practice and policy. We critically examine stan- Kristen S. Marchi, MPH dard SES measurement approaches, illustrating problems with examples from Marilyn Metzler, RN new analyses and the literature. For example, marked racial/ethnic differ- Samuel Posner, PhD ences in income at a given educational level and in at a given in- HE TERMS “SOCIOECONOMIC STA- come level raise questions about the socioeconomic comparability of indi- tus,” “socioeconomic posi- viduals who are similar on or income alone. Evidence also shows tion,” and “” (col- that conclusions about nonsocioeconomic causes of racial/ethnic differ- lectively, “SES”) are widely used ences in health may depend on the measure—eg, income, wealth, educa- inT health research, reflecting wide- tion, occupation, neighborhood socioeconomic characteristics, or past so- spread albeit often implicit recognition cioeconomic experiences—used to “control for SES,” suggesting that findings of the importance of socioeconomic fac- from studies that have measured limited aspects of SES should be reas- tors for diverse health outcomes. Most health studies that consider SES treat so- sessed. We recommend an outcome- and social group–specific approach to cioeconomic characteristics as poten- SES measurement that involves (1) considering plausible explanatory path- tial confounders of relationships be- ways and mechanisms, (2) measuring as much relevant socioeconomic in- tween other variables and health. Others formation as possible, (3) specifying the particular socioeconomic factors explicitly examine relationships be- measured (rather than SES overall), and (4) systematically considering how tween SES and health, seeking to better potentially important unmeasured socioeconomic factors may affect con- understand the associations that have clusions. Better SES measures are needed in data sources, but improve- been repeatedly observed.1-22 The so- ments could be made by using existing information more thoughtfully and cial science and social lit- erature consistently treats SES as a mul- acknowledging its limitations. tidimensional construct comprising JAMA. 2005;294:2879-2888 www.jama.com diverse socioeconomic factors (typi- cally, economic resources, power, and/or complex and multifactorial, most health variables without justifying why a given prestige).6,7,23-30 Different socioeco- studies that consider SES use a single so- measure was selected over others, with- nomic factors could affect health at dif- cioeconomic variable measured at a out explaining its meaning for a given ferent times in the life course,31-33 oper- single period and level. Often, very few analysis, and without discussing how ating at different levels (eg, individual, categories are used (eg, poor/nonpoor, household, neighborhood)30,34-37 and less than high school/high school gradu- Author Affiliations: Center on Social Disparities in Health and Department of Family and Community Medicine, through different causal path- ation or more schooling), which could University of California, San Francisco (Drs Braveman, 3,6,7,9,38-45 ways (eg, by determining expo- obscure important social gradients in Cubbin, and Egerter and Ms Marchi); and Epidemic In- sures, vulnerability, or even direct physi- health that apply across the entire so- telligence Service (Dr Chideya) and National Center for 40,42,44,45 2,8,9 Chronic Disease Prevention and Health Promotion, Di- ological effects). Socioeconomic cioeconomic spectrum. Occupation visions of Adult and Community Health (Ms Metzler) factors can interact with other social is frequently used as a measure of SES and Reproductive Health (Dr Posner), Centers for Dis- 11-14,16,17,52 ease Control and Prevention, Atlanta, Ga. characteristics, such as racial/ethnic in Europe, while income or Corresponding Author: Paula A. Braveman, MD, MPH, group and sex, to produce different education is more commonly used in the Center on Social Disparities in Health, University of 9,10,15,27,46-52 California, San Francisco, 500 Parnassus Ave, MU-3E, health effects across groups. United States. Regardless of the mea- Box 0900, San Francisco, CA 94143-0900 (braveman Despite expert consensus that SES is sure(s) used, most studies include SES @fcm.ucsf.edu).

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unmeasured socioeconomic differ- proaches to SES measurement indi- phone survey); (2) indicators of differ- ences might have affected findings. cates that these documents have not yet ent aspects of health (status, behaviors, This article critically examines sev- influenced most researchers’ prac- care) in (3) different life stages; and (4) eral widespread standard practices in tices. In many ways, this article paral- different commonly used and reason- SES measurement, discussing key con- lels a recent JAMA Editorial critiquing able measures of income and educa- cepts and providing examples to illus- the ways in which race/ethnicity is com- tion. Data sources, samples, and key SES trate problems with those practices. The monly measured in health research55 and health-related variables for the examples were chosen to illustrate SES and suggesting improved approaches new analyses are summarized in measurement issues, not to gain new based on more sound conceptualiza- TABLE 1.Weused5nationallyorstate- knowledge about the role of socioeco- tion. wide-representative data sources with nomic or other social factors in the se- well-documented strengths and limi- lected health indicators. Our goals were Methods tations: the multistate Behavioral Risk to increase awareness—not only among To illustrate key points, we selected ex- Factor Surveillance System (BRFSS), health researchers but also among amples from existing literature and from 200456; the National Health Interview policy makers and practitioners who new analyses of several national and Survey (NHIS) linked with the use health research findings—about in- statewide surveys, using the most re- National Death Index, 1989-1994, herent problems with standard meth- cent data available that were suitable for with mortality follow-up through ods of measuring and interpreting so- the desired analyses. The new analy- 1997 (mortality follow-up is not cur- cioeconomic characteristics in health ses were planned a priori to examine a rently available for later years of the research, as well as to encourage im- range of (1) widely used, high- NHIS)57;theThirdNationalHealthand proved approaches. While excellent cri- quality, population-based data sources Nutrition Examination Survey tiques have been available,10,25-28,53,54 the that represent a range of data collec- (NHANES III), 1988-1994 (both in- persistence of problematic ap- tion methods (eg, household vs tele- come and education were measured

Table 1. Summary of Data Sources, Samples, Measures of Socioeconomic Status (SES), and Dependent Variables Used in New Analyses of Health Surveys Dependent Variables Data Source Age Group, y Racial/Ethnic Groups Measures of SES* (Health-Related Indicators) Behavioral Risk Factor 18-74 (n = 255 896) Black (non-Hispanic) Poverty level Cigarette smoking Surveillance System, Hispanic Income (categories) 200456 White (non-Hispanic) Educational level Sedentary National Health Interview 18-64 (n = 380 552) Black (non-Hispanic) Poverty level Fair or poor health status Survey, 1989-1994 Mexican American Income (continuous) All-cause mortality (mortality follow-up White (non-Hispanic) Income/needs (continuous) Heart disease mortality through 1997)57 Income (quartiles) Homicide Income/needs (quartiles) Motor vehicle fatalities Educational level Education, y Third National Health and 1-5 (n = 5493) Black (non-Hispanic) Poverty level Elevated lead levels (ages 1-5 y) Nutrition Examination Ͻ17 (n = 12 388) Mexican American Income (continuous) Asthma (ages Ͻ17 y) Survey, 1988-199458 25-64 (n = 10 029) White (non-Hispanic) Educational level Cigarette smoking (ages 25-64 y) Obesity (ages 25-64 y) (ages 25-64 y) Diabetes (ages 25-64 y) National Longitudinal Study 11-21 (n = 14 282) Black (non-Hispanic) Poverty level Cigarette smoking of Adolescent Health, Cuban Income (continuous) Initiation of sexual intercourse 1994-199559 Mexican American Income/needs (continuous) Violent behavior Puerto Rican Income (quartiles) Binge drinking White (non-Hispanic) Income/needs (quartiles) Marijuana use Educational level California Maternal and Infant Ͼ24 (n = 13 952) Asian/Pacific Islander Poverty level Unintended pregnancy Health Assessment, (immigrant or US-born) Income (continuous) Delayed or no prenatal care 1999-200460 Black Income/needs (continuous) Low Latina (immigrant or US-born) Income (quartiles) Never breastfed White Income/needs (quartiles) Educational level Education, y *Poverty level indicates annual income estimated in categories defined by 100% increments of the federal poverty level according to family or household size (0%-100%, 101%- 200%, 201%-300%, 301%-400%, Ͼ400%, unknown). Income (categories) indicates annual income in categories corresponding to ranges in dollars; income (continuous), annual income in continuous dollars estimated as the midpoints of a given income range; income/needs (continuous), annual income in continuous dollars divided by family size; income (quartiles), annual income in continuous dollars grouped into empirical quartiles; and income/needs (quartiles), annual income in continuous dollars divided by family size, grouped into empirical quartiles. Educational level indicates completed education in levels according to earned credentials (Ͻ9 years, some high school, high school graduate/General Equivalency Diploma, some college, college graduate or more); for California Maternal and Infant Health Assessment, Ͻ9 years and some high school are combined; the National Longitudinal Study of Adolescent Health also includes a category for unknown education. Education, y indicates completed education in years.

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Table 2. Mean Family Income by Educational Level and Racial/ Among Adults Aged 18-64 Years—National Health Interview Survey, 1989-1994 (n = 380 552) Mean Income (95% Confidence Interval), $ Educational Level, y Black Mexican American White Overall Ͻ9 15 503 (14 851-16 154) 19 104 (17 549-20 659) 22 707 (21 935-23 479) 20 551 (19 868-21 234) 9-11 17 743 (17 051-18 434) 22 377 (20 807-23 948) 28 573 (28 062-29 083) 25 945 (25 486-26 403) 12 25 337 (24 529-26 144) 30 945 (29 791-32 098) 37 853 (37 400-38 305) 36 022 (35 613-36 432) 13-15 33 026 (31 898-34 154) 37 642 (36 089-39 195) 43 197 (42 510-43 884) 41 857 (41 228-42 487) Ն16 46 815 (45 535-48 095) 48 055 (46 137-49 973) 55 277 (54 725-55 829) 54 606 (54 064-55 149) Overall 27 937 (27 123-28 752) 27 927 (26 498-29 356) 42 113 (41 626-42 600) 39 716 (39 274-40 159)

more adequately in NHANES III than tails about methods are included in a proxy for income (or for SES overall). in the most recent NHANES data)58;the technical appendix available from the When both education and income are National Longitudinal Study of Ado- authors on request or at http://www available, researchers may hesitate to in- lescent Health (Add Health), 1994- .ucsf.edu/csdh. clude both in analytic models because 1995 (the baseline survey, when par- Race/ethnicity, regarded as a social of concerns about colinearity. Evi- ents or guardians of the adolescents construct, was assessed in the study pri- dence from the literature and our new responded to questions on income and marily to examine whether observed as- analyses indicates, however, that while education)59;andtheMaternalandIn- sociations between racial/ethnic groups standard measures of education and in- fant Health Assessment (MIHA), 1999- and health-related indicators varied by come are correlated, these correla- 2004,60 a statewide survey of postpar- the income measures, education mea- tions are generally not strong enough tum women in California supported by sures, or both used as covariables to re- to justify using education as a proxy for the California Department of Health flect SES; we also examined how a range income (or vice versa). Earnings can Services Maternal, Child and Adoles- of socioeconomic factors varied by ra- vary at similar educational levels, par- cent Health Branch.61-64 Using SAS soft- cial/ethnic group. While racial/ethnic ticularly across different social (eg, ra- ware,65 we examined correlations groups were categorized differently de- cial/ethnic, sex, age) groups. among multiple individual- or house- pending on the data source (see Table 1 For example, TABLE 2 shows, based hold-level measures of current educa- or text below), all categories were based on NHIS data, that black and Mexican tion and income. To provide addi- on self-reported information about re- American adults at every educational tional illustrative examples, we used spondents’ primary racial/ethnic iden- level had significantly lower mean in- SUDAAN software66 and the specified tification. The MIHA included Latino/ comes compared with white adults of data sources and samples to construct Hispanic as a separate racial/ethnic similar educational attainment (eg, 33% aseriesofweightedunadjustedand category; the BRFSS, NHIS, NHANES and 18% lower for those with 12 years multivariate logistic regression mod- III, and Add Health surveys included of schooling). This difference may re- els for each of 23 health-related indi- separate questions about race and His- flect not only unequal employment op- cators (listed as dependent variables in panic ethnicity, which we used to cre- portunities and rewards but varia- Table 1, counting obesity and smok- ate mutually exclusive racial/ethnic tions in educational quality.10 While ing as separate indicators in different groups. measuring credentials is generally pre- data sources or samples). These mod- ferred to years of schooling for the pur- els examined how observed associa- Critique of SES Measurement poses of reflecting SES,27,28,68,69 neither tions—expressed as odds ratios with Approaches in Health Research captures potentially dramatic differ- 95% confidence intervals —between ra- Education and Income: Not Inter- ences across schools in prestige or re- cial/ethnic groups and the health- changeable. Socioeconomic status is of- sources, which may contribute to dif- related indicators varied by the in- ten implicitly or explicitly equated with ferences in future earnings. TABLE 3 come and/or education measures (see income, especially in the United States. displays correlations between educa- Table 1 footnotes) used as covariables Despite wide recognition of its impor- tion and income (see Table 3 foot- to reflect SES; models also included age tance for health, income information is notes) overall and within racial/ethnic and sex (or parity, in MIHA), as well considered to be sensitive and is not groups for each data source or sample. as family structure (in Add Health). Ref- measured in many studies. Informa- Consistent with other studies,25,51,70,71 erence groups were those with the high- tion about education (typically mea- income-education correlations— est income or educational attainment. sured as years completed or creden- most less than 0.50—were not strong Log likelihood ratio tests were used to tials of formal schooling) is more easily enough to justify using income and edu- assess goodness of fit.67 Further de- obtained and is frequently treated as a cation as proxies for each other.

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Table 3. Spearman Correlation Coefficients Between Poverty Level and Educational Level Overall and by Racial/Ethnic Group, by Data Source and Age Group* Data Source/Age Group

BRFSS, NHIS, NHANES III, 1988-1994 Add Health, MIHA, 2004, 1989-1994, 1994-1995, 1999-2004, Race/Ethnicity 18-74 y 18-64 y† 1-5 y Ͻ17 y 25-64 y 11-21 y Ͼ24y Black 0.45 0.42 0.44 0.42 0.42 0.45 0.59 Hispanic 0.50 Mexican American 0.44 0.46 0.52 0.50 0.40 Cuban 0.42 Puerto Rican 0.37 Asian/Pacific Islander Immigrant 0.48 US-born 0.47 Latina Immigrant 0.35 US-born 0.56 White 0.41 0.37 0.54 0.50 0.40 0.44 0.49 Overall 0.48 0.41 0.58 0.55 0.44 0.48 0.67 Abbreviations: Add Health, National Longitudinal Study of Adolescent Health; BRFSS, Behavioral Risk Factor Surveillance System; MIHA, California Maternal and Infant Health Assessment; NHANES III, Third National Health and Nutrition Examination Survey; NHIS, National Health Interview Survey. *Poverty level indicates annual income estimated in categories defined by 100% increments of the federal poverty level according to family or household size (0%-100%, 101%- 200%, 201%-300%, 301%-400%, Ͼ400%, unknown); educational level indicates completed education in levels according to earned credentials (Ͻ9 years, some high school, high school graduate/General Equivalency Diploma, some college, college graduate or more); for MIHA Ͻ9 years and some high school are combined; Add Health also includes a category for unknown education. †With mortality follow-up through 1997.

cluded. Comparing blacks and whites, Table 4. Odds Ratios for Racial/Ethnic Disparities in Fair or Poor Health Among Adults Aged 18-64 Years—National Health Interview Survey, 1989-1994 (n = 380 552) higher risks were seen for blacks re- OR (95% CI)† gardless of the income or education measure used; however, the relevant SES Measure in Model* Black Non-Hispanic Mexican American odds ratios were significantly smaller None (baseline) 2.47 (2.30-2.64) 2.16 (2.01-2.32) after adjustment for income or pov- Poverty level‡ 1.65 (1.56-1.76) 1.30 (1.22-1.39) erty level. Similarly, TABLE 5 reveals dis- Income, per $1000§ 1.67 (1.57-1.78) 1.44 (1.32-1.56) parities in receipt of delayed (after the Educational level ࿣ 1.96 (1.85-2.08) 1.06 (0.99-1.14) first trimester) or no prenatal care Education, per 1 y 2.02 (1.91-2.14) 0.89 (0.82-0.97) among women who gave birth in Cali- Poverty level and educational level 1.53 (1.45-1.61) 0.86 (0.81-0.93) fornia during 1999-2004; all models Abbreviations: CI, confidence interval; OR, odds ratio; SES, socioeconomic status. *All models included race/ethnicity, age, and sex. used MIHA data and included race/ †White non-Hispanic is the reference group. ‡Annual income estimated in categories defined by 100% increments of the federal poverty level according to family or ethnicity, age, and parity. In separate household size (0%-100%, 101%-200%, 201%-300%, 301%-400%, Ͼ400%, unknown). comparisons of black and immigrant §Annual income in continuous dollars estimated as the midpoints of a given income range. ࿣Completed education in levels according to earned credentials (Ͻ9 years, some high school, high school graduate/ Latina women with white women, sig- General Equivalency Diploma, some college, college graduate or more). nificant disparities in delayed or no pre- natal care were seen when adjusting for To further illustrate practical impli- covariables (see Table 4 footnotes); all either education measure alone but not cations of treating education as an in- models included race/ethnicity, age, and when adjusting for either income mea- come proxy, we examined how con- sex. When income (measured continu- sure alone or together with education. clusions regarding racial/ethnic ously or grouped by poverty level) was Although differences often were not sta- disparities in health might vary depend- used to “adjust for SES,” Mexican tistically significant, one would have ing on whether income or education Americans appeared to be at signifi- reached different conclusions about the was used to measure SES. TABLE 4 dis- cantly increased risk of fair or poor significance, magnitude, or direction of plays results on racial/ethnic differ- health compared with non-Hispanic racial/ethnic disparities in 10 of the 23 ences in self-rated health among adults whites; however, risks appeared simi- health indicators we examined, depend- aged 18 to 64 years from 6 multivari- lar when educational level alone was in- ing on whether (or less frequently, how) ate models using NHIS data. The mod- cluded and significantly lower when income and education were mea- els differed by whether and how in- either years of education or both pov- sured. For 20 of the 23 health indica- come and education were included as erty and educational levels were in- tors, model fit was significantly better

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when both income and education were home7,29,46,80 or car46,84 ownership or a been observed in the British civil ser- included, indicating that both factors single question on “liquid assets,”83 even vice hierarchy, with individuals in each should be considered (data available after controlling for income, another so- occupational grade experiencing worse from authors on request or at cioeconomic measure, or both.7,29,46,83,84 outcomes than those in the grade im- http://www.ucsf.edu/csdh). In summary, there are strong concep- mediately above,52 even after adjust- Both income and education can in- tual and empirical grounds for measur- ing for health-related behaviors2,17; no fluence the etiology of many health out- ing wealth in health studies and for con- group was poor, and financial access to comes, in part through pathways in- cluding that income is not an adequate medical care was unlikely to account volving material resources. Education measure of wealth. for the differences. One explanation is also can reflect a range of noneco- Inadequacy of Standard US Occu- variation in the psychosocial charac- nomic social characteristics (eg, gen- pational Categories. Occupational cat- teristics of one’s occupation,17 includ- eral and health-related knowledge, lit- egories based on prestige, skills, social ing control over one’s work.17,91-93 eracy, and problem-solving skills; influence, and/or power have been the Health studies in the United States prestige; influence over others and one’s primary basis for socioeconomic clas- rarely measure occupation, however. own life)68,72-76 with important health sification in western European coun- Occupational information is included in effects; thus, for many health out- tries. Studies have repeatedly found vital statistics and some national health comes, education should be consid- strong relationships between occupa- surveys, but these data were not in- ered in addition to—not instead of— tional status using such classifications tended—and do not appear to be mean- income, accumulated wealth, and other (eg, manual vs nonmanual labor, or ingful—as SES measures, because the more directly economic factors. graded hierarchies according to pres- categories include workers with di- Income: Not a Proxy for Wealth. Im- tige or skills) and diverse health indi- verse prestige, skills, power, and/or earn- portant links between economic re- cators,2,8,12,15-17,46,84-90 even after control- ings. For example, the 2000 Standard sources and health, operating through ling for car ownership84 or income and Occupational Classification System94 diverse causal pathways, are widely rec- education.48 Stepwise gradients in mor- classifies chief executive officers, town ognized. While income is the most com- tality and cardiovascular outcomes have clerks, and tenant farmers under “Man- monly used measure of economic re- sources in affluent countries, total accumulated economic resources or Table 5. Odds Ratios for Racial/Ethnic Disparities in Delayed or No Prenatal Care Among Childbearing Women Aged 25 Years and Older—California Maternal and Infant Health “wealth” could be at least as impor- Assessment, 1999-2004 (n = 13 952) tant for health; for example, wealth can OR (95% CI)† buffer the effects of temporarily low in- come due to or illness SES Measure in Model* Black Latina Immigrant and can reflect power or influence over None (baseline) 1.86 (1.53-2.26) 2.21 (1.90-2.57) others.77 Furthermore, wealth can vary Poverty level‡ 1.16 (0.95-1.43) 1.08 (0.91-1.28) dramatically across different social Income, per $1000‡ 1.12 (0.91-1.40) 1.05 (0.88-1.26) groups with similar incomes. For ex- Educational level§ 1.57 (1.29-1.92) 1.47 (1.22-1.76) Education, per 1 y 1.72 (1.41-2.10) 1.37 (1.12-1.67) ample, TABLE 6,basedon2000data from the Census Bureau, shows that, in Poverty level and educational level 1.13 (0.91-1.39) 0.98 (0.82-1.18) Abbreviations: CI, confidence interval; OR, odds ratio; SES, socioeconomic status. the lowest income quintile, house- *All models included race/ethnicity, age, and parity. †White is the reference group. holds headed by whites had on aver- ‡See Table 4 footnotes for definition. age more than 400 times as much §Completed education in levels according to earned credentials (Ͻ9 years/some high school, high school graduate/ wealth as those headed by blacks, and General Equivalency Diploma, some college, college graduate or more). that, in higher income quintiles, whites had approximately 3 to 9 times the Table 6. Median Net Worth in Dollars (Excluding Home Equity) by Quintile of Monthly wealth of blacks; these differences were Household Income and Householder’s Racial/Ethnic Group, 2000* statistically significant (see Table 6 Quintile Black† Hispanic‡ White Non-Hispanic 78 footnotes). Lowest 57 500 24 000 7,18,25,29,46,79-84 With notable exceptions, Second 5275 5670 48 500 few health studies in affluent coun- Third 11 500 11 200 59 500 tries have measured wealth. Like in- Fourth 32 600 36 225 92 842 come, wealth can be a sensitive topic, Highest 65 141 73 032 208 023 and standard methods of calculating net *From US Census Bureau Survey of Income and Program Participation.78 Standard errors are not reported by the source; however, both the comparisons of blacks with whites and of Hispanics with whites are stated to be significantly dif- worth can be laborious. Some studies ferent. have observed wealth effects on health †Report does not indicate whether blacks are Non-Hispanic. ‡Persons of Hispanic origin may be of any race. using simpler measures such as

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lege-graduate women had been raised Figure 1. Percentage of College-Graduate Childbearing Women Aged 25 Years and Older With Ն1 College-Graduate Parent—California Maternal and Infant Health Assessment, by a college-graduate parent. Lack of 2003-2004 (n=1702) correspondence between educational attainment of women and their par- 70 ents was seen for women at all educa- 60 tional levels (data available on request 50 or at http://www.ucsf.edu/csdh). Given 1 Parent ≥ 40 the potentially important role that past socioeconomic experiences may play in 30 health outcomes, practical measures of 20 socioeconomic experiences earlier in

Percentage WithPercentage 10 life—eg, the highest educational attain-

Who Had Graduated From College Who Had Graduated From 0 ment of either parent/guardian when an Asian/Pacific Black Latina White All adult respondent was a child79,108— Islander (n = 151) (n = 226) (n = 939) (n = 1702) (n = 386) should be developed and tested in di- verse populations. Women’s Racial/Ethnic Group Importance of Neighborhood So- Error bars indicate 95% confidence intervals. cioeconomic Conditions. Accumulat- ing evidence suggests that an individu- agement” and head chefs, waitresses, and act independently or modify the ef- al’s health can be influenced by the dishwashers under “Food Preparation fects of current factors on health.13,39,100 socioeconomic characteristics of the and Serving Related.” Several au- Changes in SES over time, including neighborhood in which she or he lives, thors25-28,53 have provided detailed cri- dramatic loss of income, can affect later above and beyond her or his own indi- tiques of occupational classifications. health,90,101,102 and poverty can have cu- vidual-level SES.34-37 Socioeconomic char- Some researchers have grouped the stan- mulative health effects.99,103,104 Differ- acteristics of neighborhoods could affect dard occupational classifications into ent socioeconomic factors could be health through features of the physical manual and nonmanual work catego- more or less important at different (“built”), social, or service environ- ries and found strong associations with stages of life.83 ments109-113 via multiple pathways.114 health outcomes.48 While this may be Standard practice for measuring SES People with similar individual- or house- worthwhile when better alternatives are in most health studies, however, is to hold-level socioeconomic characteris- unavailable, more meaningful occupa- include only measures of current or re- tics can live in very different local envi- tional classifications (eg, such as ques- cent socioeconomic characteristics; ronments. For example, as seen in tions from Karasek92,93 measuring con- apart from some occupational health FIGURE 2, Add Health data show that trol and demands at work) are needed studies, socioeconomic experiences poor black and Puerto Rican adoles- to capture information about impor- during earlier life stages are rarely mea- cents (in families with incomes at or be- tant differences in occupation-related sured. Socioeconomic status in child- low the poverty line) lived in neigh- prestige or power that could affect hood generally is related to SES in adult- borhoods with higher poverty health. Occupational measures, how- hood,105-107 but important SES concentrations than their poor white ever, present challenges for classifying characteristics earlier in life (eg, par- counterparts; mean differences were persons outside the paid labor force ents’ educational attainment) may not statistically significant and similar pat- (thus disproportionately affecting wom- be reflected in measures of current SES, terns of racial/ethnic differences in en) or the chronically unemployed. particularly for some population neighborhood conditions were appar- Importance of Past Socioeconomic groups. For example, when their own ent among higher-income adolescents Experiences. Childhood SES may in- parents’ education was examined (data available on request or at http: fluence adult health independently of among women older than 24 years who //www.ucsf.edu/csdh) and among na- adult SES.6,13,31-33,79,95-99 Acknowledg- gave birth in California during 2003- tionally representative samples of ing that the relative importance of SES 2004, only 50% of college-graduate adults115 and women of reproductive early in life varies with health out- women overall had been raised by a col- age.116 comes, Smith and Ben-Shlomo13 con- lege-graduate parent. In addition, this Despite increasing recognition that cluded that “studies with data on so- percentage varied significantly across both individual- and neighborhood- cioeconomic circumstances at only one racial/ethnic groups (for all compari- level SES can influence health, few stage of life are inadequate for fully elu- sons except between blacks and Lati- health studies measure neighborhood cidating the contribution of socioeco- nas); as shown in FIGURE 1,50%of features along with—rather than as nomic factors to health and mortality Asian/Pacific Islander, 34% of black, proxies for—individual-level SES mea- risk.” Past socioeconomic factors could 20% of Latina, and 58% of white col- sures. In practice, however, many re-

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searchers could consider characteris- an even greater extent than simpler mea- Figure 2. Distribution of Neighborhood tics of both individuals and their sures, may not apply over time and across Poverty Among Poor Adolescents by neighborhoods, despite theoretical and populations.26,28 Furthermore, such com- Racial/Ethnic Group—National Longitudinal methodological challenges.117-119 By posite measures, while potentially use- Study of Adolescent Health, 1994-1995 linking residential addresses with cen- ful for classification in some studies, do –1 SD +1 SD sus geographic codes such as census not permit study of how particular SES From Mean Median From Mean tracts, census variables (eg, percent- factors influence health. Health research- ages of poor households or of unem- ers should justify the particular socio- ployed adults) can be used to describe economic measures they have studied, Racial/Ethnic Group neighborhoods; similarly, geographic avoiding claims to have measured SES Black coordinates (longitude/latitude) can be overall. Cuban linked with various data sources to de- Standard measures may not reflect im- Mexican American scribe physical environments in ways portant and relevant aspects of SES. Even Puerto Rican White that are relevant for health research. studies that include multiple standard 0 10 20 30 40 SES measures cannot examine all poten- Neighborhood Poverty, % Conclusions and tially important socioeconomic influ- Recommendations ences on health. Years of schooling re- Neighborhood poverty defined as percentage of fami- lies in the census tract who had 1989 income that was Based on the empirical evidence from ceived or earned credentials may not below the federal poverty level; poor adolescents de- new analyses and from the literature, capture significant differences in educa- fined as those aged 11-21 years and living in families with 1994 income that was at or below the federal we have reached 5 general conclu- tional quality that may also be relevant. poverty level. sions, with corresponding recommen- Conventional US occupational group- dations for improving the measure- ings were not designed and are unlikely ment and interpretation of SES in health to adequately measure job-related socio- serve racial/ethnic disparities in health studies. economic characteristics that may affect outcomes should explicitly acknowl- Different socioeconomic measures health. Subjective SES120 and experi- edge the plausible role of unmeasured 121 aspects of SES and other potentially rel- cannot be assumed to be interchange- ences of economic hardship could 55 able. The generally modest correla- plausibly influence health through psy- evant explanations, including insti- tions between income and education chophysiological pathways discussed ear- tutional or personal experiences of dis- indicate that measures of these 2 socio- lier but are not explicitly reflected in stan- crimination. We believe that economic factors are not interchange- dard SES measures. Rather than claiming conclusions from prior research about able; this is further supported by the to have “controlled for SES,” research- the nature of racial/ethnic (and other examples showing that associations ers should acknowledge the potentially social) differences in health should be between racial/ethnic groups and health relevant aspects of SES that could not be thoughtfully reassessed in light of find- indicators can depend on which socio- measured and explicitly consider the im- ings and recommendations in this ar- * economic measures are used as covari- plications of unmeasured socioeco- ticle as well as prior literature. ables. Evidence of racial/ethnic differ- nomic influences when interpreting find- A given SES measure may have dif- ences in income at a given level of ings.70 ferent meanings in different social education, in wealth at a given level of Racial/ethnic differences are likely to groups. Although our examples fo- income, in past SES at a given level of reflect unmeasured socioeconomic dif- cused on racial/ethnic differences, simi- current SES, and in neighborhood SES ferences. The concerns expressed above lar issues may apply to other social at a given level of individual SES also sup- underscore the fact that—without mea- groups categorized, for example, by age,83 sex,50,52,127 or urban/rural loca- ports the noninterchangeability of these suring all relevant SES dimensions, life 128 variables across diverse populations. stages, and aggregation levels (eg, in- tion. Whenever possible, research- Multiple socioeconomic measures often dividual, household, neighborhood, ers should examine how findings us- can be included simultaneously in mul- city)—an observed racial/ethnic dis- ing a given SES measure vary across tivariable models without colinearity parity in health cannot be considered social groups. problems20-22,61-64,70,71;stratifiedanaly- “independent of SES.”122 However, ra- Measures of SES should be selected ses also should be considered. Compos- cial/ethnic differences also cannot be as- and interpreted thoughtfully in the con- ite SES measures, or “indices,” also have sumed to be reducible to socioeco- text of plausible explanatory path- been used to reflect multiple socioeco- nomic issues; for example, systematic ways through which socioeconomic fac- nomic factors. However, few of the indi- socioeconomic differences between ra- tors may influence health. Researchers vidual- or household-level (distin- cial/ethnic groups can reflect racial dis- should select socioeconomic factors sys- guished from community-level) indices crimination at the institutional/ tematically, considering whether eco-

have been validated. Most involve mul- structural level, personal experience, or *References 10, 27, 54, 55, 70, 114, 122, 123, 125, tiple questionable assumptions and, to both.10,54,123,124 Researchers who ob- 126.

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nomic resources, education, occupa- ethnic group,55 calls for a careful reas- sity of California, San Francisco, which supported her as a Kellogg Health Disparities Scholar. tion, socioeconomic factors earlier in sessment of conclusions about the etio- Role of the Sponsors: None of the funding sources life, and neighborhood socioeco- logic basis of racial/ethnic differences for this study had any role in the design or conduct of the study; the collection, management, analysis, or in- nomic conditions at any life stage could in health based on studies with lim- terpretation of the data; or the preparation of the plausibly be relevant to the particular ited socioeconomic information. manuscript. Anonymous reviewers at the Centers for health outcome and population of in- These findings highlight the chal- Disease Control and Prevention reviewed and ap- proved the technical quality of the manuscript. The terest. They should assess the feasibil- lenges in capturing the multidimen- role of the California Department of Health Services ity of adequately measuring each po- sional nature of SES and the limita- in the collection of the data from the MIHA is noted above. tentially relevant factor using available tions of standard measures. Should we Acknowledgment: We acknowledge MCAH research- data; when a relevant factor cannot be despair of measuring SES adequately? ers Shabbir Ahmad, DVM, MPH, Eugene Takahashi, PhD, and Moreen Libet, PhD, for their contributions measured, the implications of its ex- We think not. Better measures are to the design and conduct of MIHA. We thank Nicole clusion should be considered thought- needed, along with work to develop and Wojtal and Pinal Shah, Department of Family and Com- munity Medicine, University of California, San Fran- fully and acknowledged. If a theoreti- validate measures and measurement ap- cisco (UCSF), for their assistance with research and pre- cally plausible argument or evidence proaches that are as comparable across paring the manuscript, and Roberto Vargas, MD, MPH, from previous studies indicates that a studies and populations as possible. Department of Medicine, University of California, Los Angeles, Craig Pollack, MD, Department of Medi- particular socioeconomic factor is un- However, health research could be im- cine, UCSF, and Thomas Bodenheimer, MD, Depart- likely to be relevant for the given out- proved significantly with a more con- ment of Family and Community Medicine, UCSF, for come or population of interest, it may ceptually and empirically sound ap- helpful comments on drafts. not be necessary to include that fac- proach to measurement of SES. Building tor. 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