We compared all-cause mortality rates stratified by individual-level education and by census tract area–based socioeconomic measures for Massachusetts (1999–2001). Among persons aged 25 and older, the age-adjusted relative index of inequality was slightly higher for the census tract than for the individual education measures (1.5 vs 1.2, respectively). Only the census tract socioeconomic measures could provide a relative index of inequality (2–3) for deaths before age 25 or detect expected socioeconomic disparities for deaths among persons 65 and older (relative index of inequality= approximately 1.2 vs 0.8 for census tract measures and individual education, respectively).

Population health data stratified by socioeconomic position are critical for monitoring and analyzing health disparities. When individual-level socioeconomic measures are not available, as is often the case with health surveillance data,14 an alternative approach is to use census tract area–based socioeconomic measures to characterize rates in relation to the socioeconomic position of the immediate areas in which people reside.1,36 Moreover, even when individual-level education data are available (e.g., for death certificates), the public-release census summary files before the 2000 US census did not provide data on educational level cross-tabulated by age, needed for denominators. In this study, we used the newly available 2000 census population counts for education level cross-tabulated by age to report and compare, for the first time, the socioeconomic inequalities in mortality detected with individual-level education data and census tract area–based socioeconomic measures.

We obtained mortality data, including years of individual education,7 from the state of Massachusetts for the years 1999 to 2001 (N = 165 217) and geocoded all deceased persons according to the address on the death certificate. We employed a commercial geocoding firm with known high accuracy8; thus, we were able to geocode 97% of the records with certainty to the census tract level. A priori determined categories for individual-level education and the 3 census tract area–based socioeconomic measures (percentage of persons below poverty, percentage of adults aged 25 and older with less than a high-school education, and percentage of adults aged 25 and older with a 4-year college education) are shown in Tables 1 and 2.3,4

To calculate age-standardized rates for the population aged 25 and older (Table 1), we used the US year 2000 standard million for ages 25 and older.9 We used the least deprived group as the comparison group to calculate incidence rate ratios for individual-level education and census tract area–based socioeconomic measures. We could not compute mortality rates by individual-level education for individuals younger than 25 because persons in this age group may not have completed their education, and the requisite person-year data for denominators were not available for persons younger than 18.10 On the basis of age-standardized rates, we calculated the relative index of inequality, which is a coefficient of linear slope that takes into account the effect estimate of each socioeconomic category weighted by the number of individuals in that category.1113 This measure permits meaningful comparison of health inequalities across diverse socioeconomic measures, even if their proportionate allocation of persons across socioeconomic strata differs.

Table 1 presents data on deaths, person-years, and age-standardized mortality rates for the population aged 25 and older, by individual-level education and by census tract area–based socioeconomic measure. Table 2 presents the same data for 4 age strata (0–24, 25–44, 45–64, ≥ 65). The individual-level education and census tract area–based socioeconomic measures had a similar low proportion of missing data (typically less than 3%).

For the population aged 25 and older (Table 1), the degree of socioeconomic inequality in mortality detected with the census tract area–based socioeconomic measures was slightly greater than that detected by the individual-level education measure (relative index of inequality of approximately 1.5 vs 1.2). Additionally, as shown in Table 2, only the census tract area–based socioeconomic measures yielded estimates of socioeconomic inequality for persons younger than 25 (relative index of inequality between 2.3 and 3.0). For persons aged 25 to 44, the magnitude of the relative index of inequality was greater for the individual-level education measure (6.8) compared with the census tract area–based socioeconomic measures (range = 3.3–3.7) but was similar for persons aged 45 to 64 (range = 2.7–2.9). For persons aged 65 and older, the relative index of inequality was significantly below 1 for individual-level education (0.8) but ranged between 1.2 and 1.3 for the 3 census tract area–based socioeconomic measures.

Our findings suggest that census tract area–based socioeconomic measures such as “percentage of persons below poverty” and individual-level education detect a similar magnitude of socioeconomic inequality for all-cause mortality in the state of Massachusetts for individuals between ages 45 and 64. Census tract area–based socioeconomic measures also uniquely provide evidence of socioeconomic inequality for (1) persons younger than 25 years, for whom education may not yet be completed; and (2) persons aged 65 and older, for whom individual-level education analyses indicated that mortality rates were higher among persons with 12 to 15 years of education than among those with both less than 12 and 16 or more years. However, for persons aged 25 to 44, the magnitude of the relative index of inequality for the census tract area–based socioeconomic measures, although still large (approximately 3.5), was less than that yielded by the individual-level education (6.8).

Consistent with our results, previous empirical research has reported selective misclassification in education level on death certificates, chiefly because of individuals who did not graduate from high school being reported as having obtained a high-school diploma, especially among persons aged 65 and older.15,16 The net effect is to deflate the mortality rate among persons with fewer than 12 years of education and inflate it among persons with 12 to 15 years of education.15 For this reason, the National Center for Health Statistics report Socioeconomic Status and Health provided mortality rates by individual education only for individuals between ages 25 and 64.16 Importantly, studies with self-reported individual-level educational data document socioeconomic inequality in all-cause mortality analogous to that detected with this study’s census tract area–based socioeconomic measures.17

Census tract area–based socioeconomic measures thus offer 2 advantages over individual-level education data for monitoring socioeconomic inequality in mortality. First, they provide an estimate of effect with decreased misclassification bias for persons aged 65 and older. Second, they can be used validly for persons younger than 25.

Of note, our use of census tract area–based socioeconomic measures is unlikely to be substantially affected by ecological bias, given the similar direction of estimates for the individual and area-based socioeconomic measures and results that are of a comparable magnitude (except for older ages, for which individual data are likely misclassified). From an etiological standpoint, multilevel analyses assessing the relative contribution of individual- and area-level socioeconomic characteristics to social inequities in mortality would be useful.1821 Future research also should evaluate whether our findings vary by type of mortality,22 race/ethnicity, and gender.

Table
TABLE 1— Age-Standardized All-Cause Mortality Rates, by Individual-Level Education and Census Tract Area–Based Socioeconomic Measures: Adults Aged 25 and Older, Massachusetts, 1999–2001
TABLE 1— Age-Standardized All-Cause Mortality Rates, by Individual-Level Education and Census Tract Area–Based Socioeconomic Measures: Adults Aged 25 and Older, Massachusetts, 1999–2001
 DeathsPerson-YearsaAge-Standardized Mortality Rates,b per 100 000Incident Rate Ratio (95% CI)Relative Index of Inequality(95% CI)
Individual level: education, y    1.23 (1.21, 1.26)
    ≥1622 89742558701.00 
    12–15103 182661215071.73 (1.71, 1.76) 
    < 1233 340195410161.17 (1.15, 1.19) 
Census tract level
Percentage below poverty    1.46 (1.44, 1.49)
    0.0–4.960 356541610961.00 
    5.0–9.948 999386611851.08 (1.06, 1.10) 
    10.0–19.930 098214013901.27 (1.25, 1.29) 
    20.0–10018 175137914531.33 (1.29, 1.37) 
Percentage adults 25 and older with less than a high-school education    1.53 (1.51, 1.57)
    0.0–14.988 589785711071.00 
    15.0–24.938 415284413011.18 (1.16, 1.21) 
    25.0–39.921 683150214511.31 (1.29, 1.34) 
    40.0–100894160614721.33 (1.31, 1.35) 
Percentage adults 25 and older with a bachelor’s degree    1.45 (1.43, 1.48)
    40.0–10041 315390810611.00 
    25.0–39.944 963374411721.10 (1.08, 1.13) 
    15.0–24.940 619304012761.20 (1.18, 1.22) 
    0.0–14.930 731211714351.35 (1.33, 1.37) 

Note. CI = confidence interval. Percentages missing socioeconomic data for age categories < 25, 25–44, 45–64, ≥ 65, and ≥ 25 were 100, 1.9, 1.8, 1.9, and 3.4 (for individual education); 2.6, 3.1, 3.0, 3.0, and 3.0 (for census tract poverty, census tract less than high-school education, and census tract college graduate). Person-years for individual-level education were calculated from US 2000 census summary file (SF) 3 (Table PCT025). Person-years for area-based socioeconomic measures were calculated from US 2000 census SF1 (Table P012). Area-based socioeconomic measures were calculated from US 2000 census SF3 (Table P087, % poverty; and Table P037, % with less than high-school education and % with bachelor’s degree).

aPerson-years are in thousands.

bRate is age-standardized according to the US Year 2000 standard population categories consistent with age strata of education level reported in the US 2000 census (with age categories 25–44, 45–64, and ≥ 65).

Table
TABLE 2— Age-Stratified All-Cause Mortality Rates, by Individual-Level Education and Census Tract Area–Based Socioeconomic Measures: Massachusetts, 1999–2001
TABLE 2— Age-Stratified All-Cause Mortality Rates, by Individual-Level Education and Census Tract Area–Based Socioeconomic Measures: Massachusetts, 1999–2001
 DeathsPerson-YearsaAge-Stratified Mortality Rates, per 100 000Incident Rate Ratio (95% CI)Relative Index of Inequality (95% CI)
Ages 0–24 y
Individual-level education, y    . . .
    ≥16. . .. . .. . .. . . 
    12–15. . .. . .. . .. . . 
    < 12. . .. . .. . .. . . 
Census tract–level percentage below poverty    2.33 (2.03, 2.67)
    0.0–4.98002490321.00 
    5.0–9.97291636451.38 (1.25, 1.53) 
    10.0–19.95441080501.57 (1.41, 1.75) 
    20.0–1006151032601.86 (1.67, 2.06) 
Census tract–level percentage of adults 25 and older with less than a high-school education    2.93 (2.55, 3.38)
    0.0–14.912013614331.00 
    15.0–24.96391131491.46 (1.33, 1.61) 
    25.0–39.9561894631.89 (1.71, 2.09) 
    40.0–100287418692.06 (1.81, 2.35) 
Census tract–level percentage of adults 25 and older with a bachelor’s degree    3.03 (2.64, 3.48)
    40.0–1004961852271.00 
    25.0–39.96621656401.46 (1.33, 1.61) 
    15.0–24.97161440501.89 (1.71, 2.09) 
    0.0–14.98141290632.06 (1.81, 2.35) 
Ages 25–44 y
Individual-level education, y    6.75 (6.12, 7.45)
    ≥1610612321461.00 
    12–15472330661543.37 (3.15, 3.60) 
    < 1210746031783.90 (3.58, 4.24) 
Census tract–level percentage below poverty    3.34 (3.06, 3.65)
    0.0–4.918552364781.00 
    5.0–9.9187517791051.34 (1.26, 1.43) 
    10.0–19.9155910731451.85 (1.73, 1.98) 
    20.0–10014827481982.52 (2.36, 2.70) 
Census tract–level percentage of adults 25 and older with less than a high-school education    3.72 (3.41, 4.07)
    0.0–14.929693545841.00 
    15.0–24.9173813631271.52 (1.44, 1.62) 
    25.0–39.913697531812.17 (2.04, 2.32) 
    40.0–1006953092252.69 (2.48, 2.92) 
Census tract–level percentage of adults 25 and older with a bachelor’s degree    3.63 (3.32, 3.96)
    40.0–10012311794691.00 
    25.0–39.9173517211011.52 (1.44, 1.62) 
    15.0–24.9183514081302.17 (2.04, 2.32) 
    0.0–14.9197010471882.69 (2.48, 2.92) 
Ages 45–64 y
Individual-level education, y    2.79 (2.65, 2.94)
    ≥16435614782951.00 
    12–1514 50821896622.25 (2.17, 2.33) 
    < 1233165865661.92 (1.84, 2.01) 
Census tract–level percentage below poverty    2.81 (2.67, 2.94)
0.0–4.9772219803901.00 
    5.0–9.9646112595131.31 (1.27, 1.36) 
    10.0–19.943006326801.74 (1.68, 1.81) 
    20.0–10034413858942.29 (2.20, 2.38) 
Census tract–level percentage of adults 25 and older with less than a high-school education    2.91 (2.77, 3.06)
    0.0–14.911 35427454131.00 
    15.0–24.954978896191.50 (1.45, 1.54) 
    25.0–39.935044517761.88 (1.81, 1.95) 
    40.0–10015691749002.18 (2.06, 2.29) 
Census tract–level percentage of adults 25 and older with a bachelor’s degree    2.68 (2.55, 2.81)
    40.0–100489913543611.00 
    25.0–39.9607812674801.50 (1.45, 1.54) 
    15.0–24.958209985831.88 (1.81, 1.95) 
    0.0–14.951276408012.18 (2.06, 2.29) 
  Ages65 y   
Individual-level education, y    0.80 (0.78, 0.81)
    ≥1617 48045738291.00 
    12–1583 951135761851.62 (1.59, 1.64) 
    < 1228 95076537840.99 (0.97, 1.01) 
Census tract–level percentage below poverty    1.23 (1.21, 1.26)
    0.0–4.950 779107247361.00 
    5.0–9.940 66382849111.04 (1.02, 1.05) 
    10.0–19.924 23943555721.18 (1.16, 1.20) 
    20.0–10013 25224653871.14 (1.12, 1.16) 
Census tract–level percentage of adults 25 and older with less than a high-school education    1.29 (1.27, 1.32)
    0.0–14.974 266156747401.00 
    15.0–24.931 18059252681.11 (1.10, 1.13) 
    25.0–39.916 81029856321.19 (1.17, 1.21) 
    40.0–100667712354181.14 (1.11, 1.17) 
Census tract–level percentage of adults 25 and older with a bachelor’s degree    1.24 (1.22, 1.27)
    40.0–10035 18576046301.00 
    25.0–39.937 15075649141.11 (1.10, 1.13) 
    15.0–24.932 96463451951.19 (1.17, 1.21) 
    0.0–14.923 63443054921.14 (1.11, 1.17) 

Note. CI = confidence interval. Person-years for individual-level education are calculated from US 2000 census summary file (SF) 3 (Table PCT025). Person-years for area-based socioeconomic measures are calculated from US 2000 census SF1 (Table P012). Area-based socioeconomic measures are calculated from US 2000 census SF3 (Table P087, % poverty; and Table P037, % with less than high-school education and % with bachelor’s degree).

aPerson-years are in thousands.

This work was funded by the National Institutes of Health (grant 1 R01 HD3685-01) via the National Institute of Child Health and Human Development and the Office of Behavioral and Social Science Research (Principal Investigator, Nancy Krieger). S. V. Subramanian is supported by the National Institutes of Health Career Development Award (1 K25 HL081275 )

We thank Bruce Cohen (Division of Research and Epidemiology, Massachusetts Department of Public Health) for facilitating the conduct of this study with data from the Massachusetts Health Department and for providing helpful comments. We also thank Malena Orejuela Hood (Division of Research and Epidemiology, Massachusetts Department of Public Health) and Charlene Zion (Registry of Vital Records and Statistics, Massachusetts Department of Public Health) for assistance with data handling and preparation.

Human Participant Protection Use of the data in this study was approved by all relevant institutional review boards and human subjects committees at the Harvard School of Public Health and the Massachusetts Department of Public Health.

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David H. Rehkopf, ScD, Lorna T. Haughton, PhD, Jarvis T. Chen, ScD, Pamela D. Waterman, MPH, S.V. Subramanian, PhD, and Nancy Krieger, PhDThe authors are with the Department of Society, Human Development and Health, Harvard School of Public Health, Boston, Mass. “Monitoring Socioeconomic Disparities in Death: Comparing Individual-Level Education and Area-Based Socioeconomic Measures”, American Journal of Public Health 96, no. 12 (December 1, 2006): pp. 2135-2138.

https://doi.org/10.2105/AJPH.2005.075408

PMID: 16809582