The shape of the relationship between income and self-assessed health: an international study
Open Access
- 23 November 2004
- journal article
- research article
- Published by Oxford University Press (OUP) in International Journal of Epidemiology
- Vol. 34 (2), 286-293
- https://doi.org/10.1093/ije/dyh338
Abstract
Background The relationship between income and health is usually thought to be curvilinear, but previous studies have yielded inconsistent results. We therefore examined the shape of the relationship between household equivalent income and self-assessed health in seven European countries. Methods Data were obtained from nationally representative health, level of living, or similar surveys in Belgium, Denmark, England, Finland, France, The Netherlands, and Norway and applied to men and women aged 25 years and older in the 1990s. Smooth nonparametric curves were fitted to the data, as well as a spline regression function with three linear pieces connected by two knots. Results A higher household equivalent income is associated with better self-assessed health among men and women in all countries, particularly in the middle-income range. In the higher income ranges, the relationship is generally curvilinear and characterized by less improvement in self-assessed health per unit of rising income. In the lowest income ranges, the relationship is found to be curvilinear in four countries (Belgium, Finland, The Netherlands, and Norway), where the usual deterioration of health associated with lower incomes levels off or even reverses into an improvement. Conclusions Further research is necessary to investigate the background of differences between countries in the shape of the relationship between income and self-assessed health, and should focus on both methodological and substantive explanations. Assuming causality, the results of our study lend some support to the notion of decreasing marginal health returns of a unit increase in income at the higher income ranges.Keywords
This publication has 17 references indexed in Scilit:
- The impact of income: assessing the relationship between income and health in SwedenScandinavian Journal of Public Health, 2004
- Health and LifestylesPublished by Taylor & Francis Ltd ,2003
- Determinants of health inequalities by income from the 1980s to the 1990s in FinlandJournal of Epidemiology and Community Health, 2002
- Income differences in mortality: a register-based follow-up study of three million men and womenInternational Journal of Epidemiology, 2001
- Understanding the Relationship between Income and Health: How Much Can be Gleaned from Cross‐sectional Data?Social Policy & Administration, 2001
- Understanding Income Inequalities in Health among Men and Women in Britain and FinlandInternational Journal of Health Services, 2000
- The relationship of household income to a range of health measures in three age cohorts from the West of ScotlandEuropean Journal of Public Health, 1999
- Income and health: what is the nature of the relationship?Social Science & Medicine (1982), 1999
- The shape of the relationship between income and mortality in the United States: Evidence from the National Longitudinal Mortality StudyAnnals of Epidemiology, 1996
- Health inequalities among British civil servants: the Whitehall II studyThe Lancet, 1991