Is Exposure to Income Inequality a Public Health Concern? Lagged Effects of Income Inequality on Individual and Population Health

Objective. To examine the health consequences of exposure to income inequality.
Data Sources. Secondary analysis employing data from several publicly available sources. Measures of individual health status and other individual characteristics are obtained from the March Current Population Survey (CPS). State-level income inequality is measured by the Gini coefficient based on family income, as reported by the U.S. Census Bureau and Al-Samarrie and Miller (1967) . State-level mortality rates are from the Vital Statistics of the United States ; other state-level characteristics are from U.S. census data as reported in the Statistical Abstract of the United States .
Study Design. We examine the effects of state-level income inequality lagged from 5 to 29 years on individual health by estimating probit models of poor/fair health status for samples of adults aged 25–74 in the 1995 through 1999 March CPS. We control for several individual characteristics, including educational attainment and household income, as well as regional fixed effects. We use multivariate regression to estimate the effects of income inequality lagged 10 and 20 years on state-level mortality rates for 1990, 1980, 1970, and 1960.
Principal Findings. Lagged income inequality is not significantly associated with individual health status after controlling for regional fixed effects. Lagged income inequality is not associated with all cause mortality, but associated with reduced mortality from cardiovascular disease and malignant neoplasms, after controlling for state fixed-effects.
Conclusions. In contrast to previous studies that fail to control for regional variations in health outcomes, we find little support for the contention that exposure to income inequality is detrimental to either individual or population health.     

Ethnic differences in cancer mortality trends in the US, 1950-1992

Objective. To describe long-term mortality trends by ethnicity, sex, and age for selected cancers and to assess the effect of age-adjustment using different standard populations on rate ratios and rate differences comparing black to white cancer mortality. Design. Mortality rates for selected cancers were obtained from published reports of the Vital Statistics of the United States (1950-1992). All ethnic- and sex-specific cancer rates were directly age-adjusted to the total 1970 US standard population and to a subset of the 1970 US standard population 40 years and older. Results. Over a 42-year period, lung cancer mortality increased in all population subgroups. Colorectal cancer mortality declined in whites, but increased in blacks. Prostate cancer mortality increased slightly in white men, but dramatically increased in black men. Breast cancer mortality stabilized in white women, but increased markedly in black women. Uterine cancer mortality declined for both ethnicities, while ovarian cancer mortality rates increased for both ethnicities. As expected, the ratios of the age-adjusted cancer mortality rates comparing blacks to whites were the same regardless of the age structure used as the standard population. In contrast, the differences in the age-adjusted rates between blacks and whites were greater when the age-truncated standard population was used. Conclusions. There are unexplained ethnic differences in the long-term mortality trends of selected cancers. Of particular concern are the increasing death rates in black individuals from colorectal, prostate, breast, and ovarian cancers. Since almost all deaths from these cancers occur in persons over 40, age-adjustment using an age-truncated standard population that includes only those age groups at risk should be considered, particularly when the question to be addressed is one dealing with the impact of a characteristic, such as ethnicity or sex, on mortality risk.     

Macro-to-Micro Links in the Relation between Income Inequality and Mortality

A growing literature points to links between income inequality and mortality. Any examination of the link should distinguish, both theoretically and empirically, between shifts in inequality that result from changes in the bottom and top of the income distribution. When state-level data from the U.S. censuses of 1980 and 1990 were used to measure differences in mortality, the results indicated that inequality measures reflecting depth of poverty show stronger correlations with mortality than do inequality measures reflecting heights of affluence. In addition, longitudinal data from the Panel Study of Income Dynamics were used to relate state-level inequality measures to individual-level data on mortality. This comparison revealed significant associations between degree of income inequality in state of residence and individual risk of death only for nonelderly individuals with middle-class incomes in 1990.     

Erratum to: Racial Segregation,Income Inequality,and Mortality in US Metropolitan Areas

Evidence of the association between income inequality and mortality has been mixed. Studies indicate that growing income inequalities reflect inequalities between, rather than within, racial groups. Racial segregation may play a role. We examine the role of racial segregation on the relationship between income inequality and mortality in a cross-section of US metropolitan areas. Metropolitan areas were included if they had a population of at least 100,000 and were at least 10% black (N = 107). Deaths for the time period 1991–1999 were used to calculate age-adjusted all-cause mortality rates for each metropolitan statistical area (MSA) using direct age-adjustment techniques. Multivariate least squares regression was used to examine associations for the total sample and for blacks and whites separately. Income inequality was associated with lower mortality rates among whites and higher mortality rates among blacks. There was a significant interaction between income inequality and racial segregation. A significant graded inverse income inequality/mortality association was found for MSAs with higher versus lower levels of black–white racial segregation. Effects were stronger among whites than among blacks. A positive income inequality/mortality association was found in MSAs with higher versus lower levels of Hispanic–white segregation. Uncertainty regarding the income inequality/mortality association found in previous studies may be related to the omission of important variables such as racial segregation that modify associations differently between groups. Research is needed to further elucidate the risk and protective effects of racial segregation across groups.     

Racial Segregation,Income Inequality,and Mortality in US Metropolitan Areas

Evidence of the association between income inequality and mortality has been mixed. Studies indicate that growing income inequalities reflect inequalities between, rather than within, racial groups. Racial segregation may play a role. We examine the role of racial segregation on the relationship between income inequality and mortality in a cross-section of US metropolitan areas. Metropolitan areas were included if they had a population of at least 100,000 and were at least 10% black (N = 107). Deaths for the time period 1991–1999 were used to calculate age-adjusted all-cause mortality rates for each metropolitan statistical area (MSA) using direct age-adjustment techniques. Multivariate least squares regression was used to examine associations for the total sample and for blacks and whites separately. Income inequality was associated with lower mortality rates among whites and higher mortality rates among blacks. There was a significant interaction between income inequality and racial segregation. A significant graded inverse income inequality/mortality association was found for MSAs with higher versus lower levels of black–white racial segregation. Effects were stronger among whites than among blacks. A positive income inequality/mortality association was found in MSAs with higher versus lower levels of Hispanic–white segregation. Uncertainty regarding the income inequality/mortality association found in previous studies may be related to the omission of important variables such as racial segregation that modify associations differently between groups. Research is needed to further elucidate the risk and protective effects of racial segregation across groups.     

Wide range of socioeconomic factors associated with mortality among cities in Japan

The aim of this study was to identify socioeconomic factors associated with mortality among cities in Japan. Sex-specific and age-adjusted mortality rates for 1990 and 1995 were calculated by 779 local administrative units across the nation. One hundred indicators related to socioeconomic factors were compiled and divided into eight categories: economy, education, living conditions, vegetation and open space, transport, preventive activities, medical care and demography. Composite socioeconomic indices were formulated using factor analysis of the socioeconomic indicators by category, and the association between the indices and mortality rates was examined by correlation analysis and multiple regression analysis. Nineteen composite socioeconomic indices were obtained from factor analysis, and all indices except educational expenditure-related index were significantly correlated with mortality rates. Unemployment, old housing, primary health resources and density were independently positively associated, and higher education, public library activity, health check-up participation and population growth were independently negatively associated with both 1990 and 1995 male mortality rates. For female mortality, higher income, unemployment, spacious dwelling, old housing, less vegetation, road facility, numbers of cars per population, primary health resources and density were independently positively associated, and higher education, public library activity and health check-up participation were independently negatively associated. The relationship between mortality and socioeconomic conditions was stronger in males than in females, and higher income and less vegetation were associated with higher mortality only for females. The present study demonstrated a close link between mortality and a wide range of socioeconomic conditions by using a number of indicators compiled from various data sources. The results promote a deeper understanding of socioeconomic health determinants and development of multi-sectoral health policy to improve population health.     

Not just smoking and high-tech medicine: socioeconomic inequities in U.S. mortality rates, overall and by race/ethnicity, 1960-2006

Recent research on the post-1980 widening of U.S. socioeconomic inequalities in mortality has emphasized the contribution of smoking and high-tech medicine, with some studies treating the growing inequalities as effectively inevitable. No studies, however, have analyzed long-term trends in U.S. mortality rates and inequities unrelated to smoking or due to lack of basic medical care, even as a handful have shown that U.S. socioeconomic inequalities in overall mortality shrank between the mid-1960s and 1980. The authors accordingly analyzed U.S. mortality data for 1960-2006, stratified by county income quintile and race/ethnicity, for mortality unrelated to smoking and preventable by 1960s' standards of medical care. Key findings are that relative and absolute socioeconomic inequalities in U.S. mortality unrelated to smoking and preventable by 1960s' medical care standards shrank between the 1960s and 1980 and then increased and stagnated, with absolute rates on a par with several leading causes of death, and with the burden greatest for U.S. populations of color. None of these findings can be attributed to trends in smoking-related deaths and access to high-tech medicine, and they also demonstrate that socioeconomic inequities in mortality can shrink and need not inevitably rise.     

The role of socioeconomic indicators on non-alcohol and alcohol-associated suicide mortality among women in Finland. A register-based follow-up study of 12 million person-years

This study was to analyse the effects and interrelationships of three socioeconomic indicators – education, occupation-based social class and income – on non-alcohol and alcohol-associated suicide mortality among women in Finland. The register data used comprised the 1990 census records linked to the death register for the years 1991–2001 for women who were 25–64 years old in 1990. Adjusted relative mortality rates and the relative index of inequality (RII) were estimated using Poisson regression. The study population experienced 1926 suicides, of which 563 (29%) had alcohol intoxication as a contributory cause. The age-adjusted effects of education on non-alcohol associated suicide were modest, while social class and income related inversely and strongly. The effect of social class was partly mediated by income, and social class explained income differences to some extent. The associations between these socioeconomic indicators and alcohol-associated suicide were stronger, and following adjustment for each other large effects were left for education, social class and income. Further adjustment for living arrangements had little effect on socioeconomic differences in both types of suicide, but practically all of the effects of income and some of education and social class were mediated by employment status. In conclusion, current material factors are hardly the main underlying drivers of socioeconomic differences in suicide among Finnish women. Low social class proved to be an important determinant of suicide risk, but the strong independent effect of education on alcohol-associated suicide indicates that the roots of these differences are probably established in early adulthood when educational qualifications are obtained and health-behavioural patterns set.     

Occupational hierarchy, economic sector, and mortality from cardiovascular disease among men and women. Findings from the National Longitudinal Mortality Study

PURPOSE: Although socioeconomic position has been identified as a determinant of cardiovascular disease among employed men and women in the U.S., the role of economic sector in shaping this relationship has yet to be examined. We sought to estimate the combined effects of economic sector-one of the three major sectors of the economy: finance, government and production-and socioeconomic position on cardiovascular mortality among employed men and women. METHODS: Approximately 375,000 men and women 25 years of age or more were identified from selected Current Population Surveys between 1979 and 1985. These persons were followed for cardiovascular mortality through use of the National Death Index for the years 1979 through 1989. RESULTS: In men, the lowest cardiovascular mortality was found for professionals in the finance sector (76/100,000 person/years). The highest cardiovascular mortality was found among male non-professional workers in the production sector (192/100,000 person years). A different pattern was observed among women. Professional women in the finance sector had the highest rates of cardiovascular mortality (133/100,000 person years). For both men and women, the professional/non-professional gap in cardiovascular mortality was lower in the government sector than in the production and finance sectors. These associations were strong even after adjustment for age, race and income. CONCLUSIONS: Characteristics of government, finance and production work differentially influence the risk of cardiovascular disease mortality. Men, women, professionals and non-professionals experience this risk differently.     

Rising U.S. income inequality,gender and individual self-rated health, 1972–2004

The effect of income inequality on health has been a contested topic among social scientists. Most previous research is based on cross-sectional comparisons rather than temporal comparisons. Using data from the General Social Survey and the U.S. Census Bureau, this study examines how rising income inequality affects individual self-rated health in the U.S. from 1972 to 2004. Data are analyzed using hierarchical generalized linear models. The findings suggest a significant association between income inequality and individual self-rated health. The dramatic increase in income inequality from 1972 to 2004 increases the odds of worse self-rated health by 9.4 percent. These findings hold for three measures of income inequality: the Gini coefficient, the Atkinson Index, and the Theil entropy index. Results also suggest that overall income inequality and gender-specific income inequality harm men's, but not women's, self-rated health. These findings also hold for the three measures of income inequality. These findings suggest that inattention to gender composition may explain apparent discrepancies across previous studies.     

Alaska native mortality, 1979-1998

OBJECTIVES: This study compares mortality patterns for the Alaska Native population and the U.S. white population for 1989-1998 and examines trends for the 20-year period 1979-1998. METHODS: The authors used death certificate data and Indian Health Service population estimates to calculate mortality rates for the Alaska Native population, age-adjusted to the U.S. 1940 standard million. Data on population and mortality for U.S. whites, aggregated by 10-year age groups and by gender, were obtained from the National Center for Health Statistics, and U.S. white mortality rates were age-adjusted to the U.S. 1940 standard million. RESULTS: Overall, 1989-1998 Alaska Native mortality rates were 60% higher than those for the U.S. white population for the same period. There were significant disparities for eight of 10 leading causes of death, particularly unintentional injury, suicide, and homicide/legal intervention. Although declines in injury rates can be documented for the period 1979-1998, large disparities still exist. Alaska Native death rates for cancer, cerebrovascular disease, chronic obstructive pulmonary disease, and diabetes increased from 1979 to 1998. Given decreases in some cause-specific mortality rates in the U.S. white population, increased rates among Alaska Natives have resulted in new disparities. CONCLUSIONS: These data indicate that improvements in injury mortality rates are offset by marked increases in chronic disease deaths.     

Macro-level gender equality and alcohol consumption: a multi-level analysis across U.S. States

Higher levels of women's alcohol consumption have long been attributed to increases in gender equality. However, only limited research examines the relationship between gender equality and alcohol consumption. This study examined associations between five measures of state-level gender equality and five alcohol consumption measures in the United States. Survey data regarding men's and women's alcohol consumption from the 2005 Behavioral Risk Factor Surveillance System were linked to state-level indicators of gender equality. Gender equality indicators included state-level women's socioeconomic status, gender equality in socioeconomic status, reproductive rights, policies relating to violence against women, and women's political participation. Alcohol consumption measures included past 30-day drinker status, drinking frequency, binge drinking, volume, and risky drinking. Other than drinker status, consumption is measured for drinkers only. Multi-level linear and logistic regression models adjusted for individual demographics as well as state-level income inequality, median income, and % Evangelical Protestant/Mormon. All gender equality indicators were positively associated with both women's and men's drinker status in models adjusting only for individual-level covariates; associations were not significant in models adjusting for other state-level characteristics. All other associations between gender equality and alcohol consumption were either negative or non-significant for both women and men in models adjusting for other state-level factors. Findings do not support the hypothesis that higher levels of gender equality are associated with higher levels of alcohol consumption by women or by men. In fact, most significant findings suggest that higher levels of equality are associated with less alcohol consumption overall.     

Workplace conditions, socioeconomic status, and the risk of mortality and acute myocardial infarction: the Kuopio Ischemic Heart Disease Risk Factor Study.

OBJECTIVES: This study investigated whether the association between workplace conditions and the risk of all-cause and cardiovascular mortality and acute myocardial infarction differed by socioeconomic status. METHODS: Prospective data were used to examine these associations in 2297 Finnish men, with adjustment for prevalent diseases and biological, behavioral, and psychosocial covariates, and stratified by employment status and workplace social support. RESULTS: Elevated age-adjusted relative hazards for all-cause mortality were found for men who reported high demands, low resources, and low income; high demands, high resources, and low income; and low demands, high resources, and low income. Similar patterns were found for cardiovascular mortality. In contrast, elevated age-adjusted relative hazards for acute myocardial infarction were observed only in men who reported high demands, low resources, and low income. These results did not differ by level of workplace social support or employment status. CONCLUSIONS: The negative effects of workplace conditions on mortality and of myocardial infarction risk depended on income level and were largely mediated by known risk factors.     

Path analysis of socioeconomic correlates of county infant mortality rates.

Relationships between selected socioeconomic characteristics of counties and infant mortality rates are examined. There are two research objectives: to determine the extent to which low family income, low education, sound housing, and the percentage of blacks "directly" and "jointly" relate to neonatal and postneonatal mortality rates; and to determine the degree to which a zero-order correlation between a given socioeconomic measure and general infant mortality is transmitted by neonatal and postneonatal mortality rates, respectively. Data corresponding to 2237 counties in the United States are analyzed by path analysis. Results show that the percentage of blacks and low education are two variables which have appreciable direct effects on both components of infant mortality. These two factors are also responsible in large measure for gross associations between low family income, sound housing, and rates of infant loss. On the basis of this study it is estimated that approximately two-thirds of the zero-order correlation between a given county measure of socioeconomic status and infant mortality occurs through the postneonatal component. Implications of these findings are discussed.     

The recent decline in mortality of the extreme aged: an analysis of statistical data.

Official U.S. statistics reveal a 26 per cent decline in the mortality rate for the extreme aged population (persons 85 years and over) between 1966 and 1977. This reduction was greater than that exhibited by other adult age groups and substantially larger than earlier declines for the extreme aged. This study examines the possible effect of statistical artifacts, such as errors in population estimation, on the changed mortality trend. Data from the Social Security files on Medicare enrollment are utilized to test the accuracy of population estimates for the extreme aged. Mortality rates are decomposed by selected cause of death, sex, and race to determine the influence of demographic, social, and health factors on the shift in the pattern. The results of the analysis indicate that substantial real reduction in mortality has occurred among the elderly population. Reductions among females continue to exceed those among males, but less markedly than in the past. Rates for nonwhites are subject to particularly large margins of error due to incorrect population estimates. A sharp downturn in the age-adjusted rates for the cardiovascular diseases, which are more common among the aged, appears to account for the relatively greater reduction in mortality in this age group.     

Hot spots in mortality from drug poisoning in the United States, 2007–2009

Over the past several years, the death rate associated with drug poisoning has increased by over 300% in the U.S. Drug poisoning mortality varies widely by state, but geographic variation at the substate level has largely not been explored. National mortality data (2007–2009) and small area estimation methods were used to predict age-adjusted death rates due to drug poisoning at the county level, which were then mapped in order to explore: whether drug poisoning mortality clusters by county, and where hot and cold spots occur (i.e., groups of counties that evidence extremely high or low age-adjusted death rates due to drug poisoning). Results highlight several regions of the U.S. where the burden of drug poisoning mortality is especially high. Findings may help inform efforts to address the growing problem of drug poisoning mortality by indicating where the epidemic is concentrated geographically.     

Projection of incidence rates to a larger population using ecologic variables

There is wide acceptance of direct standardization of vital rates to adjust for differing age distributions according to the representation within age categories of some referent population. One can use a similar process to standardize, and subsequently project vital rates with respect to continuous, or ratio scale ecologic variables. We obtained from the National Cancer Institute's Surveillance, Epidemiology and End Results (SEER) programme, a 10 per cent subset of the total U.S. population, country-level breast cancer incidence during 1987-1989 for white women aged 50 and over. We applied regression coefficients that relate ecologic factors to SEER incidence to the full national complement of county-level information to produce an age and ecologic factor adjusted rate that may be more representative of the U.S. than the simple age-adjusted SEER incidence. We conducted a validation study using breast cancer mortality data available for the entire U.S. and which supports the appropriateness of this method for projecting rates.     

The widening gap in death rates among income groups in the United States from 1967 to 1986.

Death rates in the United States have fallen since the 1960s, but improvements have not been shared equally by all groups. This study investigates the change in inequality in mortality by income level from 1967 to 1986. Comparable death rates are constructed for 1967 and 1986 using National Mortality Followback Surveys as numerators and National Health Interview Surveys as denominators. Direct age-adjusted death rates are calculated for income levels for the U.S. noninstitutionalized civilian population 35 to 64 years old. A summary measure of inequality in mortality adjusts for differences in the size and definition of income groups in the two years. In both 1967 and 1986, mortality decreased with each rise in income level. Measured in relative terms, this inverse relationship was greater in 1986 then in 1967 for men and women, blacks and whites. Between 1967 and 1986, death rates for those with maximal income declined between two and three times more rapidly than did rates for the middle and low income groups. The greatest increase in relative inequality was seen among white males.     

Socioeconomic inequality and its association with mortality indicators in the departments of Colombia in 2000]

OBJECTIVES: To study the inequalities in various mortality indicators for the departments of Colombia with respect to national figures, and to identify associations between the departmental mortality indicators and departmental socioeconomic indicators. METHODS: To determine mortality rates and the Gini coefficient for mortality for the departments, data from the death registry were adjusted by the estimated registry coverage for each of the departments. Five socioeconomic indicators were selected: Gini coefficient for income distribution, Human Development Index, per capita gross domestic product, per capita social investment (in health care, etc.), and percentage of the population with health care services from the country's social security system. The differences among the departments were then studied and compared to the national averages. The Spearman's rank correlation coefficient was calculated to find associations between the mortality indicators and each of the five socioeconomic indicators. RESULTS: For Colombia overall, death registry coverage was estimated at 76%, with Chocó department having the lowest coverage (35%), and Caldas department the highest (88%). The associations between the Gini coefficient for mortality and four of the socioeconomic indicators studied were significant. The national mortality rate was significantly associated with one socioeconomic indicator. Death caused by diabetes mellitus was associated with all the socioeconomic indicators; death caused by undernutrition or by diarrhea, with four socioeconomic indicators; and death from traffic accidents, with two socioeconomic indicators. Homicide was not associated with any of the socioeconomic indicators studied. CONCLUSIONS: Adjusting the death registry data produced mortality indicators that were more valid for drawing associations with socioeconomic indicators. The Gini coefficient of mortality, mortality from undernutrition, and mortality from diarrheal diseases were more suitable indicators for evaluating the inequalities among the departments because of their higher levels of association with the socioeconomic indicators. Regarding diabetes-related mortality, the associations with all the socioeconomic indicators could be due to systematic errors that lesser-developed departments made when the cause of death was being assigned. A department is a large unit for analysis, which can make it difficult to identify associations between socioeconomic indicators and deaths due to homicide or traffic accidents.     

Prostate cancer incidence and mortality rates and trends in the United States and Canada

OBJECTIVE: The purpose of this study was to compare prostate cancer incidence and mortality trends between the United States and Canada over a period of approximately 30 years. METHODS: Prostate cancer incident cases were chosen from the National Cancer Institute's Surveillance Epidemiology and End Results (SEER) Program to estimate rates for the United States white males and from the Canadian Cancer Registry for Canadian men. National vital statistics data were used for prostate cancer mortality rates for both countries, and age-adjusted and age-specific incidence and mortality rates were calculated. Joinpoint analysis was used to identify significant changes in trends over time. RESULTS: Canada and the U.S. experienced 3.0% and 2.5% growth in age-adjusted incidence from 1969-90 and 1973-85, respectively. U.S. rates accelerated in the mid- to late 1980s. Similar patterns occurred in Canada with a one-year lag. Annual age-adjusted mortality rates in Canada were increasing 1.4% per year from 1977-93 then fell 2.7% per year from 1993-99. In the U.S., annual age-adjusted mortality rates for white males increased 0.7% from 1969-1987 and 3.0% from 1987-91, then decreased 1.2% and 4.5% during the 1991-94 and 1994-99 periods, respectively. CONCLUSIONS: Recent incidence patterns observed between the U.S. and Canada suggest a strong relationship to prostate-specific antigen (PSA) test use. Clinical trials are required to determine any effects of PSA test use on prostate cancer and overall mortality.