Income and health: what is the nature of the relationship?

The aim of this article is to examine the relationship between income and morbidity, both before and after controlling for other socio-economic variables. We use data from the Health and Lifestyle Survey (first wave), a national sample survey of adults, aged 18 upwards, in England, Wales and Scotland, conducted in 1984-1985. In total, 9003 interviews were achieved. We examine the shape of the relationship between household equivalised income and height, waist-hip ratio, respiratory function (FEV1), malaise, limiting longterm illness. These indices of morbidity, both self-reported and measured, are approximately linearly related to the logarithm of income. in all except very high and low incomes (this means that increasing income is associated with better health, but that there are diminishing returns at higher levels of income). A doubling of income is associated with a similar effect on health, regardless of the point at which this occurs, providing this is within the central portion (10-90%) of the income distribution. The effect of income on the health measures is comparable to that of the other socio-economic variables in combination. The shape of the relationship found between income and health is compatible with worse health in countries with greater income inequality, without the need to postulate any direct effect of income inequality itself. (C) 1999 Elsevier Science Ltd. All rights reserved.