GENETIC PREDISPOSITION

The explanation of inequalities in health in terms of genetic factors is described as follows: because the socio-economic status of the parents is related to that of their child and because parents' health is correlated with socia-economic status, a part of socia-eco-nomic health differences in adulthood could possibly be explained by the distribution

of genetic factors in a population^l,16. This influence is a genetic disposition that runs from parent ro child, i.e. a hereditary transferable predisposition for developing a parti-cular disorder. This explanation is closely related to the selection explanation. \V'hen people who are ill gradually move down the social ladder, this will eventually result in a differential distribution of genetic material among the population with respect to illnesses that carry a genetic component. This is at the lower socio-economic groups' disadvantage²•

Although it cannot be excluded that genetic predisposition partially explains the exis-ting socio-economic inequalities in health, this mechanism is expected to be less impor-tant than the causation and selection mechanism. In support of this view it should be mentioned that there is no clear indication of a differential distribution of genetic char-acteristics among socia-economic groupSI7.IS,19.

2.1.5 CAUSATION

The ^r causation ^r mechanism assumes that a person's socio-economic status affects his/her health^10-11. This is not a direct effect however. Socio-economic status influences health through more specific determinants of health and illness. Because these determi-nants are in between socio-economic status and health, they are called intermediary factors. According to this explanation, socio-economic inequalities in health exist because lower socia-economic groups live in less favourable circumstances and more fre-quently engage in health-damaging behaviour and less frefre-quently in health- pro-moting behaviour than higher socio-economic groups. Traditionally, intermediary fac-tors are divided into material or structural facfac-tors and behavioural facfac-tors²³•

Behavioural factors

Habits such as smoking and drinking, dietary habits, physical exerciselleisure activi-ties and use of preventive and curative health care are all examples of behavioural fac-tors. \Ve expect that these factors will explain part of the socia-economic inequalities in The Netherlands because on the one hand they influence health, and on the other they are differentially distributed across socio-economic groups.

Material factors

Material aspects of living conditions that are important for the explanation of socio-economic inequalities in health are, among others, the circumstances in which a person lives and works, and his or her medical insurance. It is likely that inequalities in health partly originate because people from lower socia-economic groups, more often than people in a higher socia-economic position, live and work in circumstances that have a detrimental effect on health.

The influence of medical insurance is linked to the use of medical care. In this respect, the financial accessibility of services for example might be important (for example com-pensation/no compensation for a GP visit), as well as the rules that are imposed on the

insured party (for example periodic dental check-ups).

The explanations of socia-economic inequalities in health in terms of behavioural and material factors are not separate issues¹⁴•26

• Behavioural factors arc partly embedded in a number of material or structural living conditions. Poor dietary habits for example, or a lack ofIcisure facilities are to some extent determined by a person's financial position.

Psychosocial stress-related factors

Psychosocial stress-related £1.ctors are a third group of determinants in the explana-tion of socia-economic inequalities in health. They include stressors (long-term diffi-culties, life-events) and factors modifYing the impact of stressors on health (social sup-port, coping style, locliS of control etc.), Examples of stressors are long-term unem-ployment, death of a partner and divorce.

It is expected that part of the existing differences in health are due to the fact that lower socio-economic groups arc more exposed to stressful conditions or circumstances, or are less well equipped to cope with these stressors. As a result, the effects on their health are larger in lower groups than in higher ones^27-1S• The influence of psychosocial stress on health probably operates through a decline in physical defence which results in an increased risk of illness¹⁹-}o. That is why psychosocial stress is seen by some authors as a background to an increased susceptibility to diseases in lower socio-economic groups}!-}!. In support of this mechanism it can be argued that a negative socio-econo-Inic gradient has been demonstrated not only for some, but for many disease categories.

Social background

Over the past few years, various authors have pointed out that it is not only some-one's current socio-economic status that influences health. Material circumstances in which a person grew up might also affect adult health^U133-3-l. Nutrition and housing for example are important, not only as individual determinants but as elements of a com-plex system of material circumstances in which people grow up. Because the nomic status of a person is related to that of his/her parents, persons in lower socio-eco-nomic groups will generally have grown up in worse socia-economic circumstances than persons in higher socia-economic groups. These inequalities in material living condi-tions possibly explain a part of the differences in health later on in life by way of illness in childhood or a higher susceptibility to disease,35,

Because a direct way of measuring these material circumstances is often difHcult if not impossible. they are usually measured in an indirect way. A person's height is some-times used as an indicator^36-37,