Friday, November 13, 2009

[EQ] Income inequality, mortality, and self rated health: meta-analysis of multilevel studies


Greater equality and better health

Benefits are largest among the poor, but extend to nearly everyone

Kate E Pickett, professor of epidemiology1, Richard G Wilkinson, professor emeritus of social epidemiology2

1 Department of Health Sciences, University of York, Heslington, York
2 Division of Epidemiology and Public Health, University of Nottingham Medical School, Nottingham

Published 10 November 2009, doi:10.1136/bmj.b4320 -  BMJ 2009;339:b4320

Available online at:

“……..When the empirical evidence of the effects of inequality was confined to health, it was reasonable to think that we should not assume that inequality had any psychosocial effects before we eliminated other possible explanations. But since then the evidence base has grown. It is now clear that unequal societies have an increased prevalence of a host of social problems, including violence, bullying, teenage births, higher rates of imprisonment, low educational performance, reduced social mobility, low levels of trust, and longer working hours. Insofar as these are behavioural outcomes, they provide strong evidence that psychosocial processes are associated with inequality.

The benefits of greater equality tend to be largest among the poor but seem to extend to almost everyone.10 A more equal society might improve most people’s quality of life. Rather than merely paying lip service to creating a "classless society," it is a task for politicians and policy experts to repair our "broken society" by undoing the widening of inequalities that has taken place since the 1970s………….”



Income inequality, mortality, and self rated health: meta-analysis of multilevel studies

Naoki Kondo, assistant professor, research fellow1,2, Grace Sembajwe, research fellow3, Ichiro Kawachi, professor and chair2, Rob M van Dam, assistant professor4, S V Subramanian, associate professor2, Zentaro Yamagata, professor1

1 Department of Health Sciences, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Japan
2 Department of Society, Human Development, and Health, Harvard School of Public Health, Boston, Massachusetts USA
3 Center for Community-Based Research, Dana-Farber Cancer Institute, Boston, Massachusetts USA
4 Department of Nutrition, Harvard School of Public Health, Boston, Massachusetts  USA

Published 10 November 2009, doi:10.1136/bmj.b4471 - : BMJ 2009;339:b4471

Available online at:

To provide quantitative evaluations on the association between income inequality and health.

Design Random effects meta-analyses, calculating the overall relative risk for subsequent mortality among prospective cohort studies and the overall odds ratio for poor self rated health among cross sectional studies.


Data sources
PubMed, the ISI Web of Science, and the National Bureau for Economic Research database.


Review methods Peer reviewed papers with multilevel data.


The meta-analysis included 59 509 857 subjects in nine cohort studies and 1 280 211 subjects in 19 cross sectional studies. The overall cohort relative risk and cross sectional odds ratio (95% confidence intervals) per 0.05 unit increase in Gini coefficient, a measure of income inequality, was 1.08 (1.06 to 1.10) and 1.04 (1.02 to 1.06), respectively. Meta-regressions showed stronger associations between income inequality and the health outcomes among studies with higher Gini (0.3), conducted with data after 1990, with longer duration of follow-up (>7 years), and incorporating time lags between income inequality and outcomes. By contrast, analyses accounting for unmeasured regional characteristics showed a weaker association between income inequality and health.


The results suggest a modest adverse effect of income inequality on health, although the population impact might be larger if the association is truly causal. The results also support the threshold effect hypothesis, which posits the existence of a threshold of income inequality beyond which adverse impacts on health begin to emerge.
The findings need to be interpreted with caution given the heterogeneity between studies, as well as the attenuation of the risk estimates in analyses that attempted to control for the unmeasured characteristics of areas with high levels of income inequality. …”



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