The main problem with trying to ascertain whether it is low income or income distribution that results in poor health is that there are a number of confounding factors that should be investigated to determine the nature of the relationship. In fact many studies have shown that the relationship between income and health is not a linear one. That is increasingly higher incomes affects health positively but at a declining rate. This immediately suggests that there are other confounding factors for which we have to account for that play a spurious or artefactual role between income and health status of individuals within society. These factors are related not with low incomes but with the relative positions of those incomes within the population. Therefore we can suggest that the low income does not cause poor health directly but it is the spurious correlation of factors related to income inequality that result in poor health. Consequently there is a body of evidence discussed below which shows that egalitarian policies which reduce the income inequality reduce poor health and increase life expectancy in countries that implement them.
Since we know that there are cases where low income does not always mean poor health we can dismiss the extreme view that low income always causes poor health. However we can now address the income health relationship at the population level where we analyse the effect of individual incomes comparatively within the population and their relationship with health. We can also show the artefactual relationship between income distribution and health always occurs if the effect of the individual’s income on risk of mortality is higher at lower incomes (Gravelle 1998). This confirms that the study of this relationship cannot be done at the population level but must be done at the individual level to show the relationship of absolute and relative income. Cross sectional evidence shows a strong relationship between life expectancy and income distribution in contrast with the gross national product per head or mean income (Wilkinson 1992). Here he gives the example of Britain and Japan which illustrates the possible effects of income distribution and health showing that even though they both had similar income distributions and life expectancy in 1970 Japan has shown to have a higher life expectancy due more egalitarian approach to income distribution. However Britain has shown to have higher mortality rates due to higher income inequality. This enforces the point that health inequality is attributable to relative rather than absolute income. These results also show that we cannot link any association between income and health to be of direct causation but we must identify other confounding factors that lead to correlation between relative income and poor health.
Studies have attempted to discuss the problem of causation between health and income by showing that the variable and factors related to income tend to be collinear making their effect on health unclear (Rodgers 1979). He effectively states it is plausible to conclude that there is causation since there is an affect of income on mortality via intermittent variables. These factors such as inequality of health, educational and social background result in the distribution of income not the mean income comprising the function that results in changes of life expectancy. Hence it would be more correct to propose that the relationship between income distribution and poor health is a more spurious one. This point is enforced by a study done by Rodgers on significance testing which shows that the significance of income distribution is consistent across different countries because life expectancy at birth is higher by five to ten years in egalitarian societies as opposed to less egalitarian ones. He also rules out any insignificance on his study due to poor asymptote. These results confirm the position that increased income inequality does result in poor health as opposed to low income.
Sapolsky’s more recent study uses an psychological approach to show that stress as a result of income inequality does lead to poor health. This alternative argument would allow us to control individual income while assessing the impact of these external variables(i.e. stress and stress related illnesses). He analyses social rank in non human animals to form a basis in determining the effect of stress related physiology and stress related diseases to help him form an opinion on the stress factor in animals, which is then observed in human beings. This is based on the notion that human beings are fundamentally animals hence it is likely inherent human nature influences play a role in the determination of the health status of individuals. This would also explain why data stretching back centuries shows that each step down the socioeconomic ladder reduces the mental and physical health prospects of an individual (Sapolsky 2004). This is because as stress and stress related illnesses increases triggering a whole host of physical problems like increased smoking, drinking, obesity and negative lifestyles resulting in decline in health status. In addition decreased socioeconomic status leads to decrease in health protective measures like joining health clubs. All this suggests that feeling poorer than others are a result of established societal mechanisms that form social classes. These mechanisms seem to have an adverse impact on the psychological health of individuals at the lower income levels or lower social classes. Further studies have shown that poverty is not a strong predictor of crime as is poverty among plenty i.e. relative income. This relationship between psychological health and socioeconomic status shows that the effect of “perceived” low income on health exists only if it is compared at the individual level with that of other individuals within the same population. Only then can there be correlation with factors such as stress and perceived poverty which results in detrimental effects at each lower socioeconomic level. For example in the United states the higher the degree of income inequality the poorer the health. It is also critical to observe that in an egalitarian society the distribution of wealth would reduce the health status of the wealthy slightly though this effect is too small compared to the general effect of income inequality in less egalitarian societies. However so as to resolve any lingering doubt of this relation it is important using variable regression models we examine further the effect of these indicators accompanying income distribution in society.
From the discussion above we can see various studies have investigated the link between income and health and have shown there is no causation between low income and poor health. However the studies have shown clearly a spurious correlation exists between income distribution and poor health status. Results of logistic regression models (Kennedy 1998) indicate that factors such as health insurance status, smoking status, education status create a spurious relationship between income distribution and mortality. More importantly these models show that income distributions are associated with self rated or poor health even after mean individual income is accounted for, further enforcing the point that it is income distribution which should be considered when showing correlation with other factors to poor health.
In conclusion we can state that it is income distribution rather than low income that affects the health status of an individual. The relationship between income and health is clearly not a causal one because of the effect of intermittent variables that spuriously affects health status of individuals. We can simply visual a scenario where a person with a low income is able to have better health than an individual who has high income but feels that he is not doing well comparatively. The factors that surround income inequality create a much higher risk to poorer health incomes than those surrounding low incomes. This is a useful point to consider while trying to establish the factors that make some societies more egalitarian than others. It is also important for future studies to continue to investigate the psychological factors related to income distribution because they seem to catalyse other problems such as drug abuse which increases health problems for the individuals concerned. These negative outcomes of income inequality suggest it would be too simple to suggest that low incomes cause poor health.
Wilkinson R. G. (1992). Income distribution and life expectancy. British Medical Journal, 304, 165-168
Gravelle, H. (1998). How much of the relation between population mortality and unequal distribution of income is a statistical artefact? British Medical Journal 316, 382-385.
Kennedy, B. Pp. Kawachi, I., and Prothrow-Stith, D. (1998). Income distribution, socioeconomic status and self rated health: a U.S. multi-Level analysis. British Medical Journal, 317, 917-921
Rodgers, G.B. (1979). Income and inequality as determinants of mortality. Population Studies, 33(2), 343-351
Deaton, A. (2003). Health inequality and economic development. Journal of Economic Literature, 41(1) 113-158.
Sapolsky, R. M. (2004). Social status and health in humans and other animals. Annual Review of Anthropology, 33, 393-418.