Department of Epidemiology and Public Health, University College London, 119 Torrington Place, London WC1E 6BT, UK.
M Bartley
Abstract
Background Both social class and unemployment have been shown in many studies to be related to ill health. Recent work in social epidemiology has demonstrated the importance of examining the accumulation of disadvantage over the life course. This paper therefore uses a large longitudinal data set to examine the accumulation of both disadvantaged class and unemployment over a 20-year period in a representative sample of the male working population of England and Wales.
Methods Logistic regression.
Results Both membership of semi- or unskilled social class and unemployment in 1971 were related to limiting long-term illness (LLTI) in 1991 independently of each other, and of subsequent social class and unemployment. Any occurrence of disadvantaged social class or of unemployment added significantly to the risk of LLTI. A labour market disadvantage score comprising the number of occasions on which a study member had been either in a disadvantaged social class or unemployed showed a clear and graded relationship to illness, with odds of 4 to 1 in the worst-scoring group.
Conclusion The experiences of disadvantaged social class or unemployment at any time during this period contributed independently to an increased risk of chronic limiting illness up to 20 years later in the life course. Whereas improvements in social conditions at any one time will lessen the long-term combined impact of accumulated labour market disadvantage on health, it may not prove easy to obtain short term improvements in health inequality.
Keywords Adult, health status, longitudinal studies, unemployment, social class, socioeconomic factors, England
Accepted 3 April 2001
Relationships have frequently been demonstrated between health and both social class and unemployment in cross-sectional studies.15 However, doubts have always remained as to the value of such cross-sectional data. Because individuals may be more likely to be found in a disadvantaged social position because of their health difficulties,68 a longitudinal design is preferred when investigating relationships of social class or unemployment to health.
It is now becoming increasingly accepted that a fruitful approach to understanding the social and economic precursors of ill-health in adult life is to look for a tendency for advantages and disadvantages to accumulate over the life course of individuals. Longitudinal research has found health in mid and later adult life to be related to an accumulation of social risks, including socioeconomic disadvantage in childhood, adult social class, working conditions and unemployment.913
Longitudinal data from the Office for National Statistics' Longitudinal Study (ONS LS) make it possible to extend this work to a representative data set covering the working age male population of England and Wales. We do this by examining the relationship of limiting long-term illness (LLTI) at the time of the 1991 census of England and Wales to labour market experience, that is, occupational social class and economic position, of some 60 000 working age men over a period of 20 years, from 1971 to 1991. The accumulation of advantage and disadvantage in women needs to be addressed by a more complex analysis due to discrimination in the labour market and to women's responsibilities for unpaid domestic labour.14
Data and Methods
Data used in this paper are taken from the ONS LS. This data set links mortality and morbidity to information on social and demographic circumstances over the period 19711991 for an approximate one per cent of the population of England and Wales, some 500 000 individuals. Sampling was started at the time of the 1971 census and includes everyone born on any one of four dates of any year. It is regularly updated to include new members who are born on any of the four relevant days in each year, and events such as deaths and cancer registrations. Data are linked across decennial censuses for sample members, so that it is possible to examine changes in occupation and employment status in the periods 19711981 and 19811991. In general, information on census characteristics such as occupation is only available at the time of each census and not in between.1517 Aggregated data from the study are available to academic researchers subject to strict controls to preserve confidentiality. Included in this analysis are data for approximately 60 000 men. Numbers vary slightly between the Tables due to missing values on different variables.
Limiting long-term illness
In 1991 the census of England and Wales included, for the first time since 1911, a question on health status. The household member who fills out the census form (the household reference person) is asked, for themselves and each other household member: Does the person have any long-term illness, health problem or handicap, which limits his/her daily activities or the work, he/she can do? Include problems which are due to old age.
Social class
The measure of social position used is social class as defined by the Registrar General. This classification is described as a measure of general standing in the community based on occupational skill.18,19 Class I, professionals and owners or managers of large businesses, is regarded as the highest level, and class V, unskilled manual workers, as the lowest. Class III is divided into two subgroups: IIIN non-manual, the more routine non-manual jobs and IIIM manual, the most skilled manual jobs. Around 15% of men (10 224) in this age cohort were not able to be allocated to a social class at one or more Census points (6745 or 10.5% in 1971, 1846 or 2.9% in 1981, and 3155 or 4.9% in 1991, with some degree of overlap). The main reason for this is that the individual respondent is classified as a student, a member of the armed forces, or gives no classifiable occupation at the census. These respondents are described as having no valid social class', and are omitted from some Tables. Non-manual classes I, II and IIIN have been combined, as have the semiskilled and unskilled manual classes IV and V. This is a widely used three-way grouping of the social classes, which avoids small groups at the extremes of the distribution. At each census, social class is allocated according to the present or most recent job. Because there are 10 years between censuses, most recent may refer to a job held some time in the past.
Economic position
The term economic position is used to refer to the relationship of the individual to the labour market. The economically active are divided into those with paid employment and those who are unemployed but seeking work. The economically inactive group includes those who are permanently or temporarily sick and those who neither have, nor are seeking, paid employment for reasons other than health, for example retirement (at any age) or because of family responsibilities. In order to minimize the effect of very long term ill health causing both a history of unemployment and the report of chronic illness in 1991, all men who said they were either permanently or temporarily sick or otherwise economically inactive in 1971 or 1981 have been excluded. Economic position at the 1991 census has also been excluded from the statistical models. This is because it is possible that an illness that has occurred for the first time between 1981 and 1991 may itself have been a cause of unemployment in 1991.
Age
One problem concerning the analysis of life course data is whether the same event may have different effects according to the time in the life course at which it takes place. Power et al.11 have reported that the timing of events made no difference to their contribution to health inequality at age 33 in a representative British cohort born in 1958. In this paper, which covers a wide age group, we address this problem by testing for any interaction of measures of labour market disadvantage with age. This will indicate whether having been unemployed or in a disadvantaged social class a certain number of times has a different effect on the risk of long-term illness in men of different ages at the beginning of the period of observation.
Results
Table 1 shows patterns of employment and non-employment over the period 1971 to 1991 in men aged 1540 at the beginning of this period and therefore 3560 at the end, and who were not unable to work due to ill health in 1971 or 1981. In this Table, men who, in 1991, were out of employment for any reason (unemployment, ill health or early retirement) are included and classified as not employed. There is a great deal of movement into and out of employment: almost 75% of those unemployed in 1971 and 70% of those unemployed in 1981 were employed in 1991. However, the risk of not being in employment in 1991 is also greatly increased by prior unemployment. Over 25% of those unemployed in 1971, 30% of those unemployed in 1981, and almost 46% of those unemployed at both of these census points were also unemployed in 1991, compared to under 12% of those employed in 1971 and 1981.
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Because the measures of unemployment and disadvantaged social class were correlated (P < 0.01) but did not interact and had independent effects, they were combined into a labour market disadvantage score. Men who were off-work sick in 1991 were included in this analysis because although ill health in 1991 might cause unemployment or lower class in 1991, it could hardly have caused either unemployment or low class 20 years previously in 1971 and would be unlikely to have done so in 1981. The score has a range of 05 (0 to 2 times unemployed plus 03 times in a disadvantaged social class) and is treated as a linear term: the use of dummy variables did not appreciably improve the fit of the model. For each increase in the labour market disadvantage score, the estimated risk of LLTI was increased by 30% (OR = 1.3). Compared to those who reported neither disadvantaged class nor unemployment at any census, those who reported these at all three census points were almost four times as likely to have LLTI (OR = 3.92, 95% CI : 3.464.48).
A test for interaction between accumulated labour market disadvantage and age was significant, indicating that the relationship of labour market disadvantage to LLTI was not the same in all age groups, although this was a small effect. Figure 1 shows that accumulated labour market disadvantage tended to have a stronger effect in older men.
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This analysis adds to the existing evidence on the origins of social inequality in health over the life course.10,12,13,20,21 It differs from other studies in that it examines the full span of working age in a large representative sample of men in England and Wales. Unemployment and relatively disadvantaged social class position were seen to be related to the risk of limiting illness 20 years further on in the life course. A summary measure of labour market disadvantage was built up for individuals in an analogous way to the deprivation scores'22,23 now commonly used in studies of area variations in health and need for health services.
The cohort of men observed in this study was aged 1540 in 1971, and therefore could have remained economically active during the whole period 19711991. Those included in the statistical models were not temporarily or permanently too ill to work in 1971 or 1981 and had a valid social class measurement, which means that they will be somewhat selected for good health.24 The unemployed population has been shown to be selected for good rather than poor health.25,26 This is so even when unemployment rates are high, as at these times the size of the active labour force shrinks and the proportions of men leaving economic activity altogether for early retirement or permanent sickness increase.26,27 The inclusion of those men who were unemployed and actively seeking work in 1971 and 1981 would, if anything, act on top of the exclusion of the permanently and temporarily sick in 1971 and 1981 to ensure that selection for poor health did not play a major role in producing these results. Economic position (employed, unemployed, inactive) was observed only at the time of each of the censuses, with nothing known about this for the years in between. However, those who experience one spell of unemployment are known to be at higher risk of further spells.28,29 The tendency for the effect of unemployment to be stronger in older men is likely to be due to the fact that these intermittent indicators represent a much greater total exposure to unemployment in these men.
Adjustment for unemployment history did not greatly change the degree to which social class trajectories increased the risk of illness, while adjustment for social class trajectory had a greater effect on the relationship of unemployment to health. This confirms that unemployment acts as both a cause of increased health risk in itself, and as an indicator of an individual's position in the structure of socioeconomic advantage. That is, one reason why unemployment is associated with poor health is because of the experience of employment relations and conditions which prevail in less secure occupations.30,31 Nevertheless, these two aspects of labour market disadvantage independently retained significant and graded relationships to LLTI. The risk of illness rises with accumulations of both types of labour market disadvantage in a broadly similar way, although both have slightly different effects in different age groups.
A measure of accumulated labour market disadvantage is a useful indicator of experiences over the long term which place individuals at a higher risk of limiting illness. This is so even though the data contained in the ONS LS only show class and employment status at three discrete time points, and therefore possibly give conservative estimates of the differences between more and less disadvantaged people. These are relatively crude indicators, which can only give pointers to the precise mechanisms at work. The phenomenon of social reproduction, whereby one type of social or economic disadvantage increases the likelihood of others, is known from a wide range of other literature.32,33 Research using the 1958 British birth cohort study has shown that long or repeated spells of unemployment in young men were more likely to be experienced by those with disadvantaged circumstances in their family of origin, stretching back to childhood.34 Unemployment early in working life, in its turn, increased the risk of disadvantaged social class, relatively low income and less favourable health behaviours at age 33.35 Although the ONS LS is unique in its size and inclusion of all age groups, census information does not allow these kinds of mechanisms to be investigated in detail; however it is invaluable in confirming the broader patterns of acumulation in fully representative samples of the population.
Looking at individual measures of unemployment or disadvantaged social class shows that either experience does seem to cast long shadows forward in the words of the Black Report.36 This is relevant for the many policy initiatives presently aimed at decreasing health inequality. Short term improvements in health inequality may not prove easy to obtain in areas of large scale de-industrialization, where many citizens have experienced two decades or more of economic hardship and its social consequences.
KEY MESSAGES
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Acknowledgments
Sources of funding: ESRC Census Programme grant #H507255118; MRC Whitehall programme grant #G8802774. The authors thank the Office for National Statistics for allowing the use of the ONS Longitudinal Study and Rosemary Creeser of the LS User Support Programme at the Centre for Longitudinal Studies (CLS), Institute of Education for assistance with accessing the data. The views expressed in this publication are not necessarily those of ONS or CLS.
Notes
No reprints will be available.
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