Increasing Area Deprivation and Socioeconomic Inequalities in Heart Disease, Stroke, and Cardiovascular Disease Mortality Among Working Age Populations, United States, 1969-2011

Introduction

Cardiovascular diseases (CVD), including heart disease and stroke, have been the leading cause of death in the United States for the past eight decades.^[1] They currently account for almost a quarter of all deaths among working-age Americans, exceeded only by cancer.^[1-3] Declines in the prevalence of key risk factors such as smoking have led to a 70% drop in CVD mortality among those aged 25-64.^[1-3] Yet, substantial social inequalities in CVD mortality remain, with black Americans and those in lower socioeconomic groups continuing to experience higher CVD morbidity and mortality risks.^[1-3]

Monitoring health inequalities and their social determinants is an essential step toward development and implementation of public policies to meet national health goals, such as achieving health equity^[4,5] Although time trends in age, sex, and racial/ethnic disparities in health outcomes are widely analyzed, monitoring health inequalities, particularly those in mortality, by socioeconomic status (SES), is relatively uncommon in the US.^[1-3,6-8] This is primarily because the national mortality database contains limited and unreliable socioeconomic data for the decedents, which makes it difficult to compute mortality rates by socioeconomic characteristics^[2,3,7,8] However, linkages of national mortality data with census data at an area level, such as at the county level, have allowed several US studies to examine differentials in CVD mortality according to area-based socioeconomic deprivation level.^[6-10] Moreover, prospective linkages of census and current population survey records with national death records have permitted estimation of mortality differentials by individual-level SES characteristics such as education, income, and occupation.^[11-14]

Health inequalities in the working-age population are generally greater than those in the general population.^[7,8,14,15] Compared to the general population, those in the prime working ages between 25 and 64 years are much more vulnerable to adverse social conditions such as unemployment, marital disruption, lack of labor market opportunities, economic recession, inadequate housing, unfavorable work environment, lack of autonomy and control in the workplace, low job satisfaction, high job stress, and low social support.^[8,16] These adverse social conditions are associated with increased risks of adult premature mortality, particularly due to cardiovascular conditions.^[8,16] Few studies have explored temporal socioeconomic disparities in allcause and cause-specific mortality among working- age populations in the US.^[7,8] A previous analysis showed marked and increasing inequalities in CVD mortality by deprivation levels among Americans aged 25-64 between 1969 and 1998.^[8] The present study extends and updates that analysis by examining area socioeconomic disparities in CVD mortality from 1969 through 2011. Unlike the previous analysis, we also analyze temporal socioeconomic patterns in mortality from two main component causes, heart disease and stroke. Additionally, we estimate changes in individual-level socioeconomic inequalities in CVD, heart disease, and stroke mortality among working-age Americans between 1979 and 2002 using national longitudinal data. Temporal analysis allows us to track progress toward reducing health inequalities among those at higher risks of morbidity and mortality. It also provides important insights into the role of health-policy and medical interventions and behavioral risk factors such as such as smoking, obesity, physical inactivity, and unhealthy diet.^[5,7,8]

Methods

Results

Area Socioeconomic Trends in CVD, Heart Disease, and Stroke Mortality

Area socioeconomic gradients (rate ratios) in CVD, heart disease, and stroke mortality increased substantially during 1969-2011 (Figure 1). Compared to those in the most-affluent group, individuals in the most-deprived area group had, respectively 35%, 29%, and 73% higher CVD, heart disease, and stroke mortality in 1969, but 120-121% higher mortality in 2007-2011 (Figures 1 and 2). Socioeconomic gradients in mortality were steeper for women than for men; in 2007-2011, women had 2.5, 2.6, and 2.2 times higher CVD, heart disease, and stroke mortality, respectively, in the most-deprived group than in the most-affluent group. During 1969-2011, even though CVD mortality rates decreased by at least 59% for all deprivation groups, more deprived groups had higher CVD mortality than less deprived groups in each year/time-period (Figure 3). Cause- specific mortality declined at a much faster pace among individuals in the most affluent group than those in more deprived groups. During 1969-2011, CVD mortality in the five most-to-least deprived groups decreased at average annual rates of 2.25%, 2.71%, 2.79%, 3.10%, and 3.55%, respectively. The corresponding annual rates of decline in heart disease mortality among 5 deprivation groups were: 2.18%, 2.71%, 2.78%, 3.12%, and 3.61% and in stroke mortality: 2.89%, 3.02%, 3.13%, 3.22%, and 3.51%. In the past 4 decades, absolute socioeconomic disparities in CVD and heart disease mortality, as measured by rate differences between the most and least deprived quintiles, have remained stable, while those in stroke mortality have decreased.

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Figure 1.

Cardiovascular Disease (CVD) Mortality Among US Population Aged 25-64 Years by Area Socioeconomic Deprivation Index, 1969-2011

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Figure 2.

Heart Disease and Stroke Mortality Among US Population Aged 25-64 Years by Area Socioeconomic Deprivation Index, 1969-2011

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Figure 3.

Cardiovascular Disease (CVD), Heart Disease, and Stroke Mortality by Race/Ethnicity and Socioeconomic Deprivation Level, United States, 2007-2011

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CVD, heart disease, and stroke mortality rates decreased with decreasing levels of deprivation for both white and black populations aged 25-64, with socioeconomic gradients in CVD and heart disease mortality increasing consistently during 1969-2011 for both racial groups (data not shown for brevity). Ratio of CVD mortality between the most and least deprived quintiles increased from 1.20 in 1969 to 2.07 in 2007-2011 for whites and from 1.31 to 1.77 for blacks during 1969-2011. Similarly, the inequality ratio for stroke mortality during 1969-2011 increased from 1.26 to 2.05 for whites and from 1.55 to 1.82 for blacks. Absolute socioeconomic inequalities in CVD and heart disease mortality also widened over time for whites, but not for blacks.

Marked socioeconomic gradients in mortality existed not only for white and black Americans but also for the other major racial/ethnic groups: American Indians/Alaska Natives (AIANs), Asians/ Pacific Islanders (APIs), and Hispanics (Figure 3). During 2007-2011, heart disease mortality rates varied from a low of 18.58 deaths per 100,000 population for APIs in the least-deprived group to a high of 131.74 for blacks in the most-deprived group. Stroke mortality rates ranged from 4.71 for the most-affluent AIANs to 27.47 for the most-deprived blacks. Whites, blacks, AIANs, APIs, and Hispanics had, respectively, 2.09, 1.75, 2.60, 1.70, and 1.82 times higher heart disease mortality in the most deprived group than in the least-deprived group. Ethnic- specific deprivation gradients were similar in stroke mortality (Figure 3).

Discussion

Cardiovascular disease, heart disease, and stroke mortality rates have decreased substantially for all socioeconomic groups in the US. Against this backdrop of impressive declines in overall mortality rates, our study shows substantial and increasing socioeconomic disparities in CVD, heart disease, and stroke mortality over time, as relative inequalities in mortality among those aged 25-64 widened consistently between 1969 and 2011. Between 1969 and 2011, those in more affluent groups experienced faster declines in mortality than those in more deprived groups, which contributed to the widening socioeconomic gap in CVD, heart disease, and stroke mortality. Absolute inequalities in CVD and heart disease mortality, however, remained stable in the past 4 decades.

Socioeconomic inequalities in CVD, heart disease, and stroke mortality among the working-age population shown here are substantially greater than those for the overall US population as reported in the companion paper.²³ Such age-related patterns in socioeconomic inequalities in health and mortality have also been noted for other industrialized countries.^[7,8,24] Several hypotheses have been proposed for these patterns. First, disparities in social conditions such as education, income, wealth, unemployment, and housing and in risk factors such as smoking, physical inactivity, obesity, unhealthy diet, alcohol consumption, and hypertension tend to be more pronounced among those aged 25-64 than in the general population or among the elderly.^[3,8,24] Secondly, according to the differential selection hypothesis, individuals from the most deprived groups who survive into older ages (i.e., beyond age 65) represent an elite group who tend be healthier than their disadvantaged counterparts who perish earlier in life.^[24] As a consequence, this tends to have a narrowing effect on social inequalities in mortality at older ages, all else being equal. The third hypothesis is that, the existence of social insurance programs in the industrialized world such as Medicare and Social Security programs for elderly and retired individuals reduces social inequalities in living conditions, material wealth, and access to high-quality medical care, leading to narrower health inequalities in older ages.^[24] Whether a similar social patterning in cardiovascular-disease mortality among working- age adults and elderly exists in developing countries needs to be investigated. Individuals, especially those of retirement ages, in most low- and middle-income countries do not have access to universal health insurance or social security programs, but they might enjoy greater levels of social support and integration (a major positive determinant of health) than their counterparts in the industrialized world.

Increasing socioeconomic disparities in CVD mortality shown here are consistent with those observed previously for the United States and Europe.^[8,11,25,29] In Britain, the gap in coronary heart disease mortality among those under age 65 between the most and least deprived deciles widened between 1981 and 1995.^[27] Another study showed increasing social class inequalities in CVD mortality among men aged 15-64 in England and Wales and in Scotland during 1951 -1981 .^[28] A recent UK government study showed a widening of the social-class gradient in stroke mortality among English men aged 35-64, with the ratio between the lowest and highest social classes increasing from 1.34 in 1986-1992 to 2.67 in 1997-1999 to 2.90 in 2001-2003.^[29] Similarly, the relative inequality in ischemic heart disease mortality between the lowest and highest social classes for English men in working ages increased from 1.69 in 1986-1992 to 2.90 in 2001-2003.^[29] Like the United States, the relative gap in heart disease and stroke mortality in England widened as mortality rates fell more rapidly in higher social classes.[29] However, for Canada, although mortality rates were higher in poorer neighborhoods, both absolute and relative socioeconomic inequalities in ischemic heart disease mortality diminished between 1971 and 1996, particularly among males.^[30]

Socioeconomic disparities in CVD mortality may reflect differences in smoking prevalence, unhealthy diet, obesity, physical inactivity, and healthcare factors.^[3,7-10,31] Higher smoking rates are more prevalent among US men and women in lower socioeconomic groups and in more deprived areas.^[3,7,8,32] Smoking rates have fallen more rapidly for those in higher socioeconomic groups in the US, which largely explains temporal socioeconomic trends in CVD mortality rates. [3,8] Obesity prevalence is higher in lower socioeconomic groups, and social-class gradients in US obesity rates have persisted for the past 4 decades.^[3,33] Higher consumption of lower-quality diets and energy-dense foods and lower intakes of fruits and vegetables have been reported among lower socioeconomic groups in the US.^[3,33] Socioeconomic differences in these dietary factors have persisted or narrowed over time.^[3,33]

Marked socioeconomic disparities in CVD mortality reported here are consistent with those reported in prevalence of heart disease, stroke, and hypertension in the US.^[3,32] In 2012, those with less than a high school education had 88%, 150%, and 47% higher risk of coronary heart disease, stroke, and hypertension respectively than those with a college degree.^[32] Similarly, substantially higher prevalence of heart disease, stroke, and hypertension is reported among unemployed and low-income Americans.^[32]

Conclusions and Global Health Implications

With social inequalities and prevalence of smoking, obesity, physical inactivity, and westernization of diet on the rise, most segments of the working-age population in low- and middle-income countries will likely experience increased cardiovascular-disease burden in terms of higher morbidity and mortality rates. ^[31,34] Cardiovascular disease is the leading cause of death not only in the industrialized world, but also in low- and middle-income countries.^[31,35,36] Over 14 million premature deaths from CVD and other non-communicable diseases (NCDs) such as cancer and diabetes occur globally between the ages of 30 and 70, of which 85% are in developing countries.^[37] Most of these deaths are preventable through policy measures that are aimed at reducing behavioral risk factors such as smoking, physical inactivity, unhealthy diet, and heavy drinking that account for about 80% of cardiovascular diseases globally.^[31]

Cardiovascular disease is projected to be an even bigger health concern in the developing world.^[35] Cardiovascular-disease burden varies greatly across the world regions, with the largest number of deaths occurring in India and China, which together account for >30% of all CVD deaths in the world. The following countries have the highest disease burden (in terms of number of heart disease deaths): US and Germany among high-income countries; China and Indonesia in the East Asia and Pacific region; Russia and Ukraine in Europe and Central Asia; Brazil and Mexico in Latin America and the Caribbean; India and Pakistan in South Asia; and Nigeria and Ethiopia in Sub-Saharan Africa.^[36] Economic and workforce implications of rising CVD morbidity and mortality risks in developing countries are profound. Many of the CVD deaths among people in low- and middle- income countries occur at younger ages, often in their most productive years in the labor force; the macro-economic effect of NCDs including CVD is a reduction of 6.8% in these countries' GDPs. ^[31] Additionally, because of macro-societal forces, such as globalization and urbanization, people in developing countries are increasingly being exposed to such CVD risk factors as smoking, drinking, physical inactivity, and unhealthy diet. At the same time, they do not have similar access to public health education and prevention programs and access to primary care as their counterparts in the industrialized world.^[31] In the absence of universal healthcare coverage, poorer people with CVDs in developing countries are disproportionately burdened with high out-of-pocket expenditure, which contributes to even greater economic hardship among them.^[31]

In conclusion, we must state that much progress has been made to reduce CVD, heart disease, and stroke mortality among all socioeconomic groups in the US workforce. However, the growing socioeconomic disparities in CVD, heart disease, and stroke mortality must be seen as a major public health concern; these disparities in mortality may partly indicate that the benefits of CVD prevention and control have not reached all groups equally.^[8,31] Heart disease and stroke continue to disproportionately affect those who are unemployed and socioeconomically disadvantaged in the US workforce. The underlying social determinants of these health inequalities must be addressed.^[8,16,29,31] Tackling poverty, improving education, employment and labor market opportunities, reducing smoking prevalence and harmful use of alcohol, promoting and increasing opportunities for physical activity and access to a healthy diet, and improving access to and use of health services among those in lower socioeconomic groups and in poorer communities can reduce the risk of cardiovascular disease.^[8,29,31] Social policies with greater welfare support, better work environment, and social protection for the disadvantaged can also help reduce behavioral and psychosocial risks, leading to reduced social inequalities in CVD mortality among working-age Americans.^[8,16,29,31]