There is a variety of different definitions of social class. This is due to overwhelming evidence as there are different ways of defining health and ill health in terms of social class. Social class affects life expectancy as well as incidence of ill health and death. Evidence suggests that those in higher social class have a longer life expectancy and are healthier than those in lower social groups.
Studies such as Black Report and Acheson Report explain the relationships between social and environmental factors and health and ill health. The Black Report shows differences in health and ill health between the ruling class, middle class, working class and the underclass.
One explanation of differences in levels of illness and life expectancy is the statistical artefact explanation. Research from The Black Report argued that individuals in the working class and the underclass were more likely to be the elderly and people working in manual or more hazardous jobs such as construction. It is therefore likely for them to have a higher level of ill health than those in higher classes that work in office jobs. This suggests that the structure of age as well as what type of jobs are taken by the working class are the reasons for differences in ill health.
Another explanation is natural selection. This explanation suggests illness, infant mortality and low life expectancy are caused by poor health in lower classes, absenteeism and lack of energy needed for success. However, this has been criticised by others because evidence suggests that ill health is caused by deprivation.
Also, cultural and behavioural explanations. This focuses on the behaviour and ways of living of those in low classes. Evidence suggests that individuals in lower classes are more likely to smoke and drink heavily, eat more junk food as well as not exercise efficiently. These can potentially cause chronic illness such as heart disease, diabetes or even cancer. On the other hand, many of these individuals smoke or drink in order to deal with their difficult position in society.
Lastly, material or structural explanations. This claims that social groups that have a short life expectancy, infant mortality is high and they suffer poor health is because of inequalities in wealth and income. Low incomes is linked to poor diets and housing as well as dangerous employment such as construction. These have led to differences in health.