Commentary: Using innovative inequality measures in epidemiology

Trends in Income Inequities in Cardiovascular Health Among US Adults, 1988-2018

BACKGROUND

Mean cardiovascular health has improved over the past several decades in the United States, but it is unclear whether the benefit is shared equitably. This study examined 30-year trends in cardiovascular health using a suite of income equity metrics to provide a comprehensive picture of cardiovascular income equity.

METHODS

The study evaluated data from the 1988-2018 National Health and Nutrition Examination Survey. Survey groupings were stratified by poverty-to-income ratio (PIR) category, and the mean predicted 10-year risk of a major cardiovascular event or death based on the pooled cohort equations (PCE) was calculated (10-year PCE risk). Equity metrics including the relative and absolute concentration indices and the achievement index-metrics that assess both the prevalence and the distribution of a health measure across different socioeconomic categories-were calculated.

RESULTS

A total of 26 633 participants aged 40 to 75 years were included (mean age, 53.0-55.5 years; women, 51.9%-53.0%). From 1988-1994 to 2015-2018, the mean 10-year PCE risk improved from 7.8% to 6.4% (P<0.05). The improvement was limited to the 2 highest income categories (10-year PCE risk for PIR 5: 7.7%-5.1%, P<0.05; PIR 3-4.99: 7.6%-6.1%, P<0.05). The 10-year PCE risk for the lowest income category (PIR <1) did not significantly change (8.1%-8.7%). In 1988-1994, the 10-year PCE risk for PIR <1 was 6% higher than PIR 5; by 2015-2018, this relative inequity increased to 70% (P<0.05). When using metrics that account for all income categories, the achievement index improved (8.0%-7.1%, P<0.05); however, the achievement index was consistently higher than the mean 10-year PCE risk, indicating the poor persistently had a greater share of adverse health.

CONCLUSIONS

In this serial cross-sectional survey of US adults spanning 30 years, the population's mean 10-year PCE risk improved, but the improvement was not felt equally across the income spectrum.

On absolute socioeconomic health inequality comparisons

This paper introduces a new graphical tool: the mean deviation concentration curve. Using a unified approach, we derive the associated dominance conditions that identify robust rankings of absolute socioeconomic health inequality for all indices obeying Bleichrodt and van Doorslaer's (J Health Econ 25:945-957, 2006) principle of income-related health transfer. We also derive dominance conditions that are compatible with other transfer principles available in the literature. To make the identification of all robust orderings implementable using survey data, we discuss statistical inference for these dominance tests. To illustrate the empirical relevance of the proposed approach, we compare joint distributions of income and health-related behavior in the United States.

Socioeconomic inequalities in health care utilization in Paraguay: Description of trends from 1999 to 2018

Objective

Paraguay’s health care system is characterized by segmented provision and low public spending, with limited coverage and asymmetries in terms of access and quality of care. The present study provides national estimates of income-related inequality in health care utilization and trends in the country over the past two decades.

Methods

Using data from the Paraguayan Permanent Household Survey, we estimated socioeconomic inequality in health care use during the period 1999–2018. We used poverty-to-income ratio as the socioeconomic stratifier and defined health care use as having reported a health problem and subsequent health care use in the last 90 days before interview. Inequality was summarized by rank- and level-based versions of the Concentration Index for binary outcomes.

Results

Inequalities affecting those with lower incomes were present in all years assessed, although the magnitude of these inequalities declined over time. Inequality as expressed by the rank-based index decreased from 0.209 (95%CI 0.164; 0.253) in 1999 to 0.032 (95%CI -0.010; 0.075) in 2018. The level-based index decreased from 0.076 (95%CI -0.029; 0.182) in 1999 to 0.024 (0.002; 0.045) in 2018. Trends in both indices were generally stable from 1999 to 2009, with a noticeable decrease in 2010. The sharpest decreases relative to the 1999 baseline were observed in the period 2010–2018, reflecting changes in health care use and income distribution. Stratification by area, sex and older people suggest similar trends within subgroups.

Conclusions

Decreases in inequality coincide temporally with increments in public health expenditure, removal of user fees in public health care facilities and the expansion of conditional cash-transfer programmes. Future research should disentangle the role of each of these policies in explaining the trends described.

Why caesarean is more unequally concentrated among better-off people in Tehran? A concentration index decomposition approach

BACKGROUND

Iran, as one of the low-income and middle-income countries, has experienced a remarkable increase in the caesarean section (CS) rate during the past three decades. Although several studies have been conducted on the prevalence and risk factors affecting CS, but few studies were done regarding socioeconomic factors influencing the CS rate. The aim of this study was to identify socioeconomic inequalities and its determinants in CS in Tehran, capital of Iran.

METHODS

A population-based cross-sectional study was conducted on 5170 pregnancies in Tehran, since 2015. Principal component analysis was applied to measure the asset-based economic status. Concentration index was used to measure socioeconomic inequality in CS and then decomposed in to its determinants.

RESULTS

The concentration index and its 95% CI for CS history was 0.102 (0.091 to 0.112). Decomposition of the concentration index showed that economic status had the largest contribution (49.2%) to socioeconomic inequality in CS. Mother's education (14.9%), father's occupation (13.3%) and father's nationality (9.7%) had the next high positive contribution to measured inequality in CS, respectively.

CONCLUSIONS

CS is mostly concentrated among women with high economic status. The identified contributing factors should be addressed to decrease the socioeconomic inequalities as possible.

Unequal distribution of health human resource in mainland China: what are the determinants from a comprehensive perspective?

Background

The inequality of health human resource is a worldwide problem, and solving it also is one of the major goals of China’s recent health system reform. Yet there is a huge disparity among cities in mainland China. The aim of this study is to analyze the distribution inequality of the health human resource in 322 prefecture-level cities of mainland China in 2014, and to reveal the facets and causes of the inequalities.

Methods

The data for this study were acquired from the provincial and municipal Health Statistics Yearbook (2014) and Statistical Yearbook (2014), the municipal National Economic Bulletin (2014), and the official websites of municipal governments, involving 322 prefecture-level cities. Meanwhile, Concentration Index was used to measure the magnitude of the unequal distribution of health human resource. A decomposition analysis was employed to quantify the contribution of each determinant to the total inequality.

Results

The overall concentration index of doctors and nurses in mainland China in 2014 was 0.1038 (95% CI = 0.0208, 0.1865) and 0.0785 (95% CI =0.0018, 0.1561). Decomposition of the concentration index revealed that economic status was the primary contributor (58.5% and 57%) to the inequality of doctors and nurses, followed by the Southwest China (19.1% and 18.6%), urbanization level (− 13.1% and − 12.8%), and revenue (8.0% and 7.8%). Party secretaries with Master degree (7.0%, 6.8%), mayors who were 60 years old or above (6.3%, 6.1%) also were proved to be a major contributor to the inequality of health human resource.

Conclusions

There was inequality of health human resource distribution which was pro-rich in mainland China in 2014. Economic status of the cities accounted for most of the existing inequality, followed by the Southwest China, urbanization level, revenue, party secretaries with Master degree, and mayors who were 60 years old or above in respective importance. Besides, the party secretaries and mayors also had certain influence on the allocation of health human resource. The tough issue of HHR inequality should be addressed by comprehensive measures from a multidisciplinary perspective.

Ability of ecological deprivation indices to measure social inequalities in a French cohort

Background

Despite the increasing interest in place effect to explain health inequalities, there is currently no consensus on which kind of area-based socioeconomic measures researchers should use to assess neighborhood socioeconomic position (SEP). The study aimed to evaluate the reliability of different area-based deprivation indices (DIs) in capturing socioeconomic residential conditions of French elderly women cohort.

Methods

We assessed area-based SEP using 3 DIs: Townsend Index, French European Deprivation Index (FEDI) and French Deprivation index (FDep), among women from E3N (Etude épidémiologique auprès des femmes de la Mutuelle Générale de l’Education Nationale). DIs were derived from the 2009 French census at IRIS level (smallest geographical units in France). Educational level was used to evaluate individual-SEP. To evaluate external validity of the 3 DIs, associations between two well-established socially patterned outcomes among French elderly women (smoking and overweight) and SEP, were compared. Odd ratios were computed with generalized estimating equations to control for clustering effects from participants within the same IRIS.

Results

The analysis was performed among 63,888 women (aged 64, 47% ever smokers and 30% overweight). Substantial agreement was observed between the two French DIs (Kappa coefficient = 0.61) and between Townsend and FEDI (0.74) and fair agreement between Townsend and FDep (0.21). As expected among French elderly women, those with lower educational level were significantly less prone to be ever smoker (Low vs. High; OR [95% CI] = 0.43 [0.40–0.46]) and more prone to being overweight (1.89 [1.77–2.01]) than women higher educated. FDep showed expected associations at area-level for both smoking (most deprived vs. least deprived quintile; 0.77 [0.73–0.81]) and overweight (1.52 [1.44–1.62]). For FEDI opposite associations with smoking (1.13 [1.07–1.19]) and expected association with overweight (1.20 [1.13–1.28]) were observed. Townsend showed opposite associations to those expected for both smoking and overweight (1.51 [1.43–1.59]; 0.93 [0.88–0.99], respectively).

Conclusion

FDep seemed reliable to capture socioeconomic residential conditions of the E3N women, more educated in average than general French population. Results varied strongly according to the DI with unexpected results for some of them, which suggested the importance to test external validity before studying social disparities in health in specific populations.

Electronic supplementary material

The online version of this article (10.1186/s12889-017-4967-3) contains supplementary material, which is available to authorized users.

Understanding determinants of unequal distribution of stillbirth in Tehran, Iran: a concentration index decomposition approach

OBJECTIVE

The present inquiry set to determine the economic inequality in history of stillbirth and understanding determinants of unequal distribution of stillbirth in Tehran, Iran.

METHODS

A population-based cross-sectional study was conducted on 5170 pregnancies in Tehran, Iran, since 2015. Principal component analysis (PCA) was applied to measure the asset-based economic status. Concentration index was used to measure socioeconomic inequality in stillbirth and then decomposed into its determinants.

RESULTS

The concentration index and its 95% CI for stillbirth was -0.121 (-0.235 to -0.002). Decomposition of the concentration index showed that mother's education (50%), mother's occupation (30%), economic status (26%) and father's age (12%) had the highest positive contributions to measured inequality in stillbirth history in Tehran. Mother's age (17%) had the highest negative contribution to inequality.

CONCLUSIONS

Stillbirth is unequally distributed among Iranian women and is mostly concentrated among low economic status people. Mother-related factors had the highest positive and negative contributions to inequality, highlighting specific interventions for mothers to redress inequality.

Changes in Socio-Economic Inequality in Neonatal Mortality in Iran Between 1995-2000 and 2005-2010: An Oaxaca Decomposition Analysis

BACKGROUND

Exploring changes in health inequality and its determinants over time is of policy interest. Accordingly, this study aimed to decompose inequality in neonatal mortality into its contributing factors and then explore changes from 1995-2000 to 2005-2010 in Iran.

METHODS

Required data were drawn from two Iran's demographic and health survey (DHS) conducted in 2000 and 2010. Normalized concentration index (CI) was used to measure the magnitude of inequality in neonatal mortality. The contribution of various determinants to inequality was estimated by decomposing concentration indices in 1995-2000 and 2005-2010. Finally, changes in inequality were investigated using Oaxaca-type decomposition technique.

RESULTS

Pro-rich inequality in neonatal mortality was declined by 16%, ie, the normalized CI dropped from -0.1490 in 1995-2000 to -0.1254 in 2005-2010. The largest contribution to inequality was attributable to mother's education (32%) and household's economic status (49%) in 1995-2000 and 2005-2010, respectively. Changes in mother's educational level (121%), use of skilled birth attendants (79%), mother's age at the delivery time (25-34 years old) (54%) and using modern contraceptive (29%) were mainly accountable for the decrease in inequality in neonatal mortality.

CONCLUSION

Policy actions on improving households' economic status and maternal education, especially in rural areas, may have led to the reduction in neonatal mortality inequality in Iran.

Comparing inequalities in oral and general health: findings of the Canadian Health Measures Survey

OBJECTIVE

The aim of this study was to measure and compare the magnitude of income-related inequalities for oral and general health outcomes in Canada.

METHODS

Data for this study were from the 2007/09 Canadian Health Measures Survey (CHMS). The sample size consisted of 3,413 Canadians aged 18-79 (1,601 men and 1,812 women). Oral health indicators were the total number of decayed and missing teeth. General health was measured as obesity and high blood pressure. Socio-economic status was measured as equivalized household income. We used the concentration index (CI) to quantify income-related inequalities in these outcomes. Values for the concentration index range from -1 to +1 with negative (or positive) concentration indices showing that the outcome is more concentrated among the less well off (or among the better off). All statistical analyses were weight-adjusted for the complex survey design and standardized for age.

RESULTS

The concentration indices for oral health outcomes (decayed teeth = -0.25, missing teeth = -0.15) were greater than for general health outcomes (obesity = -0.05, high blood pressure = -0.04). The concentration indices for oral health outcomes, in contrast to general health outcomes, were statistically significant.

CONCLUSION

There were income-related inequalities for oral health outcomes with the disease concentrated more among the poor. Inequalities in oral health were greater than inequalities in general health. The variation in the funding of oral health care and general health care is likely to explain the differences in the magnitude of income-related inequalities for oral and general health.

Equity in the distribution of CT and MRI in China: a panel analysis

INTRODUCTION

China is facing a daunting challenge to health equity in the context of rapid economic development. This study adds to the literature by examining equity in the distribution of high-technology medical equipment, such as CT and MRI, in China.

METHODS

A panel analysis was conducted with information about four study sites in 2006 and 2009. The four provincial-level study sites included Shanghai, Zhejiang, Shaanxi, and Hunan, representing different geographical, economic, and medical technology levels in China. A random sample of 71 hospitals was selected from the four sites. Data were collected through questionnaire surveys. Equity status was assessed in terms of CT and MRI numbers, characteristics of machine, and financing sources. The assessment was conducted at multiple levels, including international, provincial, city, and hospital level. In addition to comparison among the study sites, the sample was compared with OECD countries in CT and MRI distributions.

RESULTS

China had lower numbers of CTs and MRIs per million population in 2009 than most of the selected OECD countries while the increases in its CT and MRI numbers from 2006 to 2009 were higher than most of the OECD countries. The equity status of CT distribution remained at low inequality level in both 2006 and 2009 while the equity status of MRI distribution improved from high inequality in 2006 to moderate inequality in 2009. Despite the equity improvement, the distributions of CTs and MRIs were significantly positively correlated with economic development level across all cities in the four study sites in either 2006 or 2009. Our analysis also revealed that Shanghai, the study site with the highest level of economic development, had more advanced CT and MRI machine, more imported CTs and MRIs, and higher government subsidies on these two types of equipment.

CONCLUSIONS

The number of CTs and MRIs increased considerably in China from 2006 to 2009. The equity status of CTs was better than that of MRIs although the equity status in MRI distribution got improved from 2006 to 2009. Still considerable inequality exists in terms of characteristics and financing of CTs and MRIs.

A dual Atkinson measure of socioeconomic inequality of health

The Atkinson index of income inequality is based on a comparison of the average income with the equivalent income, where the equivalent income is defined as the level of income that, if given to everyone, would generate the same social welfare as the existing distribution of income. This paper explores the possibility of extending this approach to the measurement of socioeconomic inequality of health. It assumes a social evaluation function that depends upon two variables: socioeconomic status as well as health status. With a general form of this function, an Atkinson measure is derived, which gives exactly the same result when applied to the socioeconomic variable and when applied to the health variable. The paper examines the properties of the index and suggests various extensions.

Understanding determinants of socioeconomic inequality in mental health in Iran's capital, Tehran: a concentration index decomposition approach

BACKGROUND

Mental health is of special importance regarding socioeconomic inequalities in health. On the one hand, mental health status mediates the relationship between economic inequality and health; on the other hand, mental health as an "end state" is affected by social factors and socioeconomic inequality. In spite of this, in examining socioeconomic inequalities in health, mental health has attracted less attention than physical health. As a first attempt in Iran, the objectives of this paper were to measure socioeconomic inequality in mental health, and then to untangle and quantify the contributions of potential determinants of mental health to the measured socioeconomic inequality.

METHODS

In a cross-sectional observational study, mental health data were taken from an Urban Health Equity Assessment and Response Tool (Urban HEART) survey, conducted on 22 300 Tehran households in 2007 and covering people aged 15 and above. Principal component analysis was used to measure the economic status of households. As a measure of socioeconomic inequality, a concentration index of mental health was applied and decomposed into its determinants.

RESULTS

The overall concentration index of mental health in Tehran was -0.0673 (95% CI = -0.070 - -0.057). Decomposition of the concentration index revealed that economic status made the largest contribution (44.7%) to socioeconomic inequality in mental health. Educational status (13.4%), age group (13.1%), district of residence (12.5%) and employment status (6.5%) also proved further important contributors to the inequality.

CONCLUSIONS

Socioeconomic inequalities exist in mental health status in Iran's capital, Tehran. Since the root of this avoidable inequality is in sectors outside the health system, a holistic mental health policy approach which includes social and economic determinants should be adopted to redress the inequitable distribution of mental health.

Measuring socioeconomic inequality in health, health care and health financing by means of rank-dependent indices: a recipe for good practice

The tools to be used and other choices to be made when measuring socioeconomic inequalities with rank-dependent inequality indices have recently been debated in this journal. This paper adds to this debate by stressing the importance of the measurement scale, by providing formal proofs of several issues in the debate, and by lifting the curtain on the confusing debate between adherents of absolute versus relative health differences. We end this paper with a 'matrix' that provides guidelines on the usefulness of several rank-dependent inequality indices under varying circumstances.

The role of adolescent behaviors in the female-male disparity in obesity incidence in US black and white young adults

In the United States, black women are at much greater risk for obesity than black men. We explored whether adolescent behaviors (family dinners, hours of television, playing sports with mother, playing sports with father, bouts of physical activity) were associated with gender disparity in 6-year obesity incidence in young adulthood. We used data from the nationally representative National Longitudinal Study of Adolescent Health to examine adolescent behaviors in nonimmigrant black (n = 1,503) and white (n = 4,452) youths in 1994-95 (aged 11-19 years) and 1995-96 (aged 12-20). We assessed gender disparity in obesity incidence (female incidence minus male incidence) during young adulthood (2001-02; aged 18-26). Standardized gender disparities were calculated using race- and gender-stratified, covariate-adjusted logistic regression models in which males and females were set to the same distributions of adolescent behaviors. In adolescence, black females reported less leisure-time physical activity and lower likelihood of playing sports with either parent compared with black males. Setting adolescent behaviors equal for black males and females did not reduce the estimated gender disparity in obesity incidence (nonstandardized: 9.8 percentage points (95% confidence interval (CI): 4.5, 15.1); fully standardized: 10.2 percentage points (5.2, 15.2)). There was little gender disparity in whites before or after adjustments. To our knowledge, this is the first study to examine to what extent behavioral differences during adolescence might account for gender disparity in obesity incidence in black young adults. Male-female differences in these adolescent behaviors did not appear to underlie the gender gap in young adult obesity.

Income-related health inequalities in Canada and the United States: a decomposition analysis

OBJECTIVES

We examined income-related inequalities in self-reported health in the United States and Canada and the extent to which they are associated with individual-level risk factors and health care system characteristics.

METHODS

We estimated income inequalities with concentration indexes and curves derived from comparable survey data from the 2002 to 2003 Joint Canada-US Survey of Health. Inequalities were then decomposed by regression and decomposition analysis to distinguish the contributions of various factors.

RESULTS

The distribution of income accounted for close to half of income-related health inequalities in both the United States and Canada. Health care system factors (e.g., unmet needs and health insurance status) and risk factors (e.g., physical inactivity and obesity) contributed more to income-related health inequalities in the United States than to those in Canada.

CONCLUSIONS

Individual-level health risk factors and health care system characteristics have similar associations with health status in both countries, but they both are far more prevalent and much more concentrated among lower-income groups in the United States than in Canada.