The influence of adult ill health on occupational class mobility and mobility out of and into employment in The Netherlands

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Abstract

In the debate about the explanation of socio-economic health inequalities one of the important issues is the relative importance of health selection. The aim of this study was to investigate to what extent occupational class mobility and mobility out of and into employment are health-related, and in addition, to estimate the contribution of health-related social mobility to socio-economic health differences in the working population. Data were taken from the Longitudinal Study on Socio-Economic Health Differences in the Netherlands, which started in 1991; follow-up data were collected in 1995. The analysis is based on 2533 persons aged 15–59 at baseline.

The influence of health problems in 1991 (perceived general health, health complaints and chronic conditions) on changes in occupational class between 1991 and 1995 was negligible. Neither upward nor downward mobility was affected by health problems. However, health problems in 1991 were significantly associated with a higher risk of mobility out of employment and a lower risk of mobility into employment in 1995. For example, for mobility out of employment among persons that reported at least one chronic condition in 1991, the odds ratio was 1.46. Health-related mobility out of employment substantially influences the estimate of socio-economic health inequalities in the working population (measured by current occupation). For manual workers, as compared to non-manual workers, the odds ratio for a less-than-good perceived general health was underestimated by 34% in 1995. Selective mobility into employment overestimates socio-economic inequalities in health in the working population by 9%. Respondents that moved into and out of employment were healthier than those that remained economically inactive, but their health was worse than of those that remained employed (both manual and non-manual).

Implications for health policy are that the prospects for people with health problems to stay in paid employment should be improved.

Introduction

Differences in health between socio-economic groups were established in several industrialised countries, for different socio-economic indicators and different health measurements. One of the issues discussed in the explanation of these differences is the relative importance of two mechanisms: social causation and selection (West, 1991). Social causation means that socio-economic inequalities in health are caused by the unequal distribution of lifestyle factors, structural factors or psycho-social factors across socio-economic groups. The health selection mechanism implies that health affects social mobility: healthy people may move up, and unhealthy people may move down in the social hierarchy. This hypothesis is also referred to as the “drift hypothesis” (Townsend and Davidson, 1982).

Most literature suggests that the relative importance of selection on physical health in the explanation of socio-economic inequalities in health is small (Fox et al., 1985, Lundberg, 1991, Blane, 1993, Davey Smith et al., 1994, Power et al., 1996), although it has also been argued that the contribution might be substantial (West, 1991). More research on selection was done with respect to mental illness. Evidence is in favour of the existence of a certain degree of mental health-related social mobility, both in the Netherlands and in other countries (a.o. Dohrenwend, 1975, Wiersma et al., 1983). However, evidence in this field is also ambiguous (Fox, 1990), and so far, its contribution to the explanation of socio-economic inequalities in health remains unknown.

Although in the Black Report (Townsend and Davidson, 1982) the health selection explanation focuses on intragenerational class mobility (mobility of an individual compared to his or her own occupational class earlier in life), much of the recent selection debate refers to intergenerational class mobility (mobility of an individual compared to the occupational class of his or her parents) (e.g. West, 1991, Rahkonen et al., 1997). Evidence with respect to intragenerational class mobility is mostly based on cross-sectional data or mortality follow-up studies, while longitudinal studies on this subject are scarce. Results from the British OPCS longitudinal study suggest that health-related mobility between classes has little effect on mortality differentials (Goldblatt, 1988, Goldblatt, 1989, Davey Smith et al., 1994). Others, however, defend that selective mobility could play a role (a.o. Carr-Hill, 1987, Goldblatt, 1989).

Hardly any evidence is available on intragenerational class mobility with respect to health indicators other than mortality. Most of these studies used a case-control design. E.g. support was provided for downward class mobility among bronchitis and asthma patients (Meadows, 1961, McClellan and Garrett, 1990).

There are only a few studies in which the relation between health and intragenerational class mobility is studied directly, i.e. using prospective longitudinal data. Lundberg, 1988, Lundberg, 1991 studied occupational class mobility in a Swedish cohort, covering a period of about 10 years and using questionnaires about health and occupational status. He concluded that intragenerational mobility was not influenced by health status. Power et al. (1996), who used data from the 1958 British Birth Cohort, found that class mobility between the ages 23 and 33 was influenced by health status. They concluded, however, that health selection was not important in the explanation of adult health differences. This is mainly due to the small number of people with poor health who are mobile between classes.

The scarcely available literature suggesting that intragenerational health selection is important focuses on health-related mobility into and out of employment (Bartley and Owen, 1996). This is also called the ‘healthy worker effect’ (a.o. Vinni and Hakama, 1980, Dahl, 1993), which implies that this mobility causes the working population to be healthier than those who are economically inactive. Selection into and out of paid employment due to health reasons is suggested to be the most important form of health-related social mobility (Rahkonen et al., 1997). Rather than taking up a lower status of occupation, those in poor health may leave employment (Blane, 1993). It may be that this mobility out of employment occurs more in lower occupational classes. If so, health selection out of employment will influence the extent of class differences in health in the working population.

Effects of health emerge in different forms of mobility out of the labour market, i.e. early retirement, becoming a housewife or receiving a disability pension, or mobility into unemployment. Data from The Netherlands show that the risk of disability and unemployment was higher among workers with more sick leave (De Winter, 1992). Research among housewives in the USA and Sweden showed that good health was related to taking up employment, and ill health was related to leaving employment (Waldron, 1980, Vagerö and Lahelma, 1996). Most research, however, focuses on (un)employment. Results from a Swedish study show that illness had an obvious effect on mobility into unemployment before the normal age of retirement (Lundberg, 1991). Several authors suggest that health selection plays a role in the association between (un)employment and health outcomes (Schwefel, 1986, Kessler et al., 1987, Bartley, 1988, Spruit, 1989) but others found no or only limited support for this hypothesis (Moser et al., 1984, Martikainen, 1990). An effect of ill health on duration of employment and the chance of reemployment has also been reported (Claussen et al., 1993, Arrow, 1984).

Similar to research on occupational class mobility, however, many designs of the studies described above show shortcomings because they use cross-sectional or retrospective data.

It is recommended that further studies on health-related social mobility should not only examine occupational class mobility but also health-related mobility into and out of employment, preferably on the basis of a longitudinal design (Rahkonen et al., 1997). The Longitudinal Study on Socio-Economic Health Differences (LS-SEHD) in the Netherlands offers such an opportunity, because data on adult health, occupational status and position in employment are available at different points in time. Effects of health-related occupational class mobility and mobility out of and into employment can be examined in a prospective cohort study among men and women, aged 15–59 year at baseline.

The research question in this paper is as follows: to what extent are health problems at adult age related to downward or upward occupational class mobility and mobility out of and into employment? In addition, we estimated the contribution of health-related selection to the explanation of socio-economic health differences in the working population.

Section snippets

Data and methods

The Longitudinal Study on Socio-Economic Health Differences (LS-SEHD) is a prospective cohort study of the explanation of socio-economic health differences in The Netherlands. The design and objective of the LS-SEHD are described in detail elsewhere (Mackenbach et al., 1994). The study is based on a cohort of 15–74 years old, noninstitutionalized Dutch nationals, living in the city of Eindhoven and surroundings (a region in the south–east of The Netherlands). At the time of the start of the

Results

For ease of reference results are shown for the total population, as no major differences were found between men and women. Significant differences between both sexes will be indicated. Table 1 gives the absolute numbers with respect to occupational class mobility and mobility out of and into employment.

In Table 2 occupational class mobility in the period 1991–1995 is presented in relation to the three health indicators. In general mobility of people turned out to be more upward (N=114, 12% of

Discussion

Health in 1991, after a follow-up time of 4.5 years, is not related to occupational class mobility, neither upward nor downward. However, health is related to mobility out of and into employment. Health inequalities among the working population (measured by current occupation) are substantially influenced by mobility into and out of employment. We estimated that socio-economic inequalities in health among the working population are ‘underestimated’ by approximately 34% due to mobility out of

Acknowledgements

The LS-SEHD is financially supported by the Ministry of Public Health, Welfare and Sports and the Prevention Fund. It forms part of the GLOBE-study (‘Gezondheid en Levensomstandigheden Bevolking Eindhoven en omstreken’). The GLOBE-study is performed by the Department of Public Health of the Erasmus University Rotterdam, in collaboration with the Public Health Services of the city of Eindhoven and the region of south–east Brabant.

The authors wish to thank Inez Joung for her valuable comments on

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