ArticlesIncome inequality, the psychosocial environment, and health: comparisons of wealthy nations
Introduction
There has been great interest in understanding links between income inequality and health.1, 2, 3, 4 Some studies have examined income inequality in relation to between-country health differences,5, 6 while others have analysed associations of income inequality and health within countries.7, 8 Two distinct questions have been raised. First, for a given average income, is the extent of inequality in the distribution of income associated with differences in average population health between countries or between regions (eg, states) within a country? As an extension of this question, it has been proposed that the quality of the psychosocial environment—characterised by such things as social capital and sense of control over life—is the main explanatory mechanism for such associations.1, 6, 9 Although there is evidence at the individual level that psychosocial factors, like distrust,10 control,11 and the quality of interpersonal relationships12 affect health, little is known about whether population level analogues of these psychosocial factors explain health differences between countries. Such psychosocial indicators have been shown as unimportant in understanding between country differences in self-rated health.13 The second question is that if an association does exist between income inequality and health at the population level, to what extent is that association the mathematical result of the underlying association between income and health at an individual level.14, 15 Several within USA studies have investigated aspects of this.15, 16 The present analyses investigate the first question.
The theory that income inequality, and its potential effect on aspects of the psychosocial environment, can account for international health differences has become influential for interpreting health inequalities and in a number of countries has been embraced in policy documents focused on strategies to improve population health.3 Interest in the health effects of unequal income distribution was generated by the observation that income inequality was strongly associated with life expectancy among nine Organisation for Economic Cooperation and Development (OECD) nations.5 These data from the late 1970s and early 1980s showed that more economically unequal countries like the USA and UK had lower life expectancy than more egalitarian Nordic countries. After publication of this provocative idea, concerns were raised about accuracy of the income data, and contrary findings were published.17, 18, 19, 20, 21 Despite the fact that these studies produced inconsistent findings, the theory that income inequality and its psychosocial effects are critical determinants of population health continues to be generally accepted and widely promoted.22, 23, 24
Important questions remain about the underlying empirical evidence to support claims that countries with more income inequality and poorer psychosocial environment have worse population health. Previous research has been based on small numbers of countries and limited health indicators, such as life expectancy—a synthetic, overall measure of population health which can mask differences in the age and cause of death structure between countries. Across Europe, between country differences in the cause of death structure have been shown to be important in interpreting differences in the extent of within country health inequalities.25
We aimed to assess associations between income inequality and low birthweight, life expectancy, self-rated health, and age-specific and cause-specific mortality among countries providing data in wave III of the Luxembourg Income Study (LIS). The LIS is widely regarded as the premier study of income distribution in the world.26 We have also examined how aspects of the psychosocial environment such as distrust, belonging to organisations, volunteering (all proposed as measures of social capital,27 and perceived control over one's life circumstances were associated with between-country variations in health. We have also included data on belonging to trade unions and the proportion of women elected to national government, as indicators of class relations within the labour market and broader sociopolitical participation of women.28
Section snippets
Country selection
Wave III (1989–92) of the LIS provides the most recent, complete income inequality data available and includes 23 countries—Taiwan, Czech republic, Hungary, Israel, Poland, Russia, Slovak republic, Australia, Belgium, Canada, Denmark, Finland, France, Germany, Italy, Luxembourg, Netherlands, Norway, Spain, Sweden, Switzerland, UK, and USA. Taiwan was excluded because health data were not available. We first examined income inequality and life expectancy among the remaining 22 countries.
Results
We first examined data on income inequality and life expectancy for 22 countries in the wave III LIS database, As we have argued elsewhere, when data points are few, the selection of countries can be crucial to interpretation of results.34 Thus, we have presented data from all available countries in figure 1, which shows that income inequality was strongly and negatively associated with life expectancy (p=0·0001). However, this association was largely induced by the data point for Russia, where
Discussion
There are inherent limitations in interpreting associations based on sixteen, or fewer observations. To illustrate this point, in figure 2A we have selected the nine countries that were used in the 19925 study which reported a correlation of r=0·86 between more equal income distribution and life expectancy from data for the late 1970s and early 1980s. When we used these same nine countries but analysed data for 1989–92, higher income inequality was associated with lower life expectancy, albeit
References (37)
- et al.
Contribution of job control and other risk factors to social variations in coronary heart disease incidence
Lancet
(1997) - et al.
Income inequality and population health
Soc Sci Med
(1998) Improvement of social environment to improve health
Lancer
(1998)Unhealthy societies: the afflictions of inequality
(1996)Income inequality and mortality: why are they related? Income inequality goes hand in hand with underinvestment in human resources
BMJ
(1996)- et al.
Income inequality and mortality: importance to health of individual income, psychosocial environment, or material conditions
BMJ
(2000) - et al.
Income inequality and health: what does the literature tell us?
Anmt Rev Public Health
(2000) Income distribution and life expectancy
BMJ
(1992)- et al.
International comparators and poverty and health in Europe
BMJ
(2000) - et al.
Inequality in income and mortality in the United States: analysis of mortality and potential pathways
BMJ
(1996)
Income distribution and mortality: cross-sectional ecological study of the Robin Hood index in the United States
BMJ
Social capital, income inequality, and mortality
Am J Public Health
Hostility and increased risk of mortality and acute myocardial infarction: the mediating role of behavioural risk factors
Am J Epidenriol
Social functioning and overall mortality: prospective evidence from the Kuopio Ischaemic Heart Disease Risk Factor Study
Epidemiology
Inequality, social trust, and self-reported health status in high-income countries
Ann New York Academy Sci
How much of the relation between population mortality and unequal distribution of income is a statistical artifact?
BMJ
The relationship between income inequality and mortality is not a statistical artefact
BMJ
Poverty or income inequality as predictors of mortality: longitudinal cohort study
BMJ
Cited by (346)
Radioactive decay, health and social capital: Lessons from the Chernobyl experiment
2022, Journal of Economic Behavior and OrganizationCitation Excerpt :In recent years, the literature has increasingly focused on the relationship between social capital and health (Macinko and Starfield, 2001; Kawachi et al., 2004). A number of contributions suggested a negative correlation between social capital and mortality rates (Kawachi et al., 1997; Wilkinson et al., 1998; Kennedy et al., 1998; Veenstra, 2002; Lochner et al., 2003; Skrabski et al., 2003; Kennelly et al., 2003), psychiatric disorders (Veenstra, 2002) and suicide rates (Helliwell, 2007), and a positive correlation with self-rated health (Lynch et al., 2001; Subramanian et al., 2001; 2002; Wen et al., 2003). The most recent literature has recognized that the relationship between the social capital and health may be characterised by reverse causality and that policy implications derived from simple empirical correlations may be misleading.
Cervical cancer prevention in Africa: A policy analysis
2022, Journal of Cancer Policy