European Journal of Epidemiology

, Volume 30, Issue 8, pp 627–636 | Cite as

A Swiss paradox? Higher income inequality of municipalities is associated with lower mortality in Switzerland

  • Kerri M. Clough-Gorr
  • Matthias Egger
  • Adrian Spoerri
SOCIAL EPIDEMIOLOGY

Abstract

It has long been surmised that income inequality within a society negatively affects public health. However, more recent studies suggest there is no association, especially when analyzing small areas. This study aimed to evaluate the effect of income inequality on mortality in Switzerland using the Gini index on municipality level. The study population included all individuals >30 years at the 2000 Swiss census (N = 4,689,545) living in 2,740 municipalities with 35.5 million person-years of follow-up and 456,211 deaths over follow-up. Cox proportional hazard regression models were adjusted for age, gender, marital status, nationality, urbanization, and language region. Results were reported as hazard ratios (HR) with 95 % confidence intervals. The mean Gini index across all municipalities was 0.377 (standard deviation 0.062, range 0.202–0.785). Larger cities, high-income municipalities and tourist areas had higher Gini indices. Higher income inequality was consistently associated with lower mortality risk, except for death from external causes. Adjusting for sex, marital status, nationality, urbanization and language region only slightly attenuated effects. In fully adjusted models, hazards of all-cause mortality by increasing Gini index quintile were HR = 0.99 (0.98–1.00), HR = 0.98 (0.97–0.99), HR = 0.95 (0.94–0.96), HR = 0.91 (0.90–0.92) compared to the lowest quintile. The relationship of income inequality with mortality in Switzerland is contradictory to what has been found in other developed high-income countries. Our results challenge current beliefs about the effect of income inequality on mortality on small area level. Further investigation is required to expose the underlying relationship between income inequality and population health.

Keywords

Income Income inequality Gini index Mortality Switzerland 

Notes

Acknowledgments

This manuscript contains original material not previously published. We thank the Swiss Federal Statistical Office for providing mortality and census data and for the support which made the Swiss National Cohort and this study possible. This work was supported by the Swiss National Science Foundation (Grant Nos. 3347CO-108806, 33CS30_134273 and 33CS30_148415). The members of the Swiss National Cohort Study Group are Matthias Egger (Chairman of the Executive Board), Adrian Spoerri and Marcel Zwahlen (all Bern), Milo Puhan (Chairman of the Scientific Board) and Matthias Bopp (both Zurich), Nino Künzli (Basel), Fred Paccaud (Lausanne) and Michel Oris (Geneva). We also thank Kali Tal for her editorial contribution and Rudi Peters from the FTA for his helpful comments. This work was supported by funds from the Swiss National Science Foundation (Grant Number 33CSC0_134273). The sponsors had no role in study design, methods, data collection, analysis, or paper preparation.

Conflict of interest

None of the authors has a conflict of interest.

Supplementary material

10654_2015_9987_MOESM1_ESM.docx (59 kb)
Supplementary material 1 (DOCX 60 kb)

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Copyright information

© Springer Science+Business Media Dordrecht 2015

Authors and Affiliations

  • Kerri M. Clough-Gorr
    • 1
    • 2
  • Matthias Egger
    • 1
    • 3
  • Adrian Spoerri
    • 1
  1. 1.Institute of Social and Preventive Medicine (ISPM)University of BernBernSwitzerland
  2. 2.Section of GeriatricsBoston University Medical CenterBostonUSA
  3. 3.School of Social and Community MedicineUniversity of BristolBristolUK

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