The European Journal of Public Health Advance Access originally published online on July 28, 2005
The European Journal of Public Health 2005 15(5):518-522; doi:10.1093/eurpub/cki038
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Health Inequalities |
Can large relative mortality differences between socio-economic groups among Swedish men be explained by risk indicator-associated social mobility?
Tomas Hemmingsson* and Ingvar Lundberg* Department of Public Health Sciences, Karolinska Institute, Stockholm and National Institute for Working Life, Stockholm, Sweden
Correspondence: Tomas Hemmingsson, PhD, National Institute for Working Life, SE-113 91 Stockholm, Sweden, tel: +46 8 6563025, fax: +46 8 6196906, e-mail: tomas.hemmingsson{at}niwl.se
Received July 10, 2003, accepted July 9, 2004
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Background: The Nordic countries, profiled as welfare states, are shown to have comparatively large relative socio-economic differences in mortality and comparatively high intergenerational mobility. The aim of this study was to analyse the role of risk indicator-associated social mobility (from childhood through to adulthood) in socio-economic mortality differences among Swedish men aged 35–50 years. Methods: We used data on risk indicators for adult mortality (risk use of alcohol, smoking, low emotional control, psychiatric diagnosis, medication for nervous problems, contact with police and child care, experience of unemployment, low body height, low education) collected at compulsory conscription for military training among Swedish men at aged 18–20, fathers' socio-economic status at subjects' ages 9–11 years, data on subjects' socio-economic status at ages 34–36 years, and follow-up data on mortality during 1986–1999 (at ages 35–50 years). Results: Persons in manual occupations in 1985 showed an elevated relative risk (RR) of mortality compared with stable non-manual employees regardless of the social position of their father (RR 1.75 among stable manual workers, and RR 1.74 among the downwardly mobile). In multivariate analyses, taking into account the risk indicators first operating in late adolescence, the increased mortality risk among stable manual workers and also among the downwardly mobile diminished considerably (RR 1.32 and 1.39, respectively). Conclusions: These results suggest that a substantial part of the socio-economic differences in mortality among middle-aged men had their origin in childhood circumstances. Risk indicator-associated social mobility was found to contribute substantially to an increase in the relative difference in mortality between male manual workers and non-manual employees.
Keywords: mortality, socio-economic position, risk indicator-associated social mobility
Despite improvements in living circumstances and health care in industrialized countries, socio-economic inequalities in mortality persist. Several studies have even suggested that socio-economic differences in mortality have increased over the last decades.1,2 There is also recent evidence that socio-economic differences in mortality, as well as morbidity, are more pronounced in the Nordic countries than in many other European countries.3,4 Such findings are puzzling, since the comparatively egalitarian social, economic and health-care policies of countries like Sweden and Norway have previously been regarded as leading to relatively small inequalities in health.3,5
One possible explanation for the more pronounced relative inequality in mortality in Sweden lies in the fact that countries differ with regard to degree of social mobility. In ‘open’ societies, a person's achieved social position may be less dependent on the socio-economic position of his or her parents, and more dependent on personal characteristics, which may include health and health-related factors. Through social mobility, people with better aptitudes or qualifications would reach higher positions regardless of class of origin. The other side of the coin is that those less able or qualified would end up in a low position regardless of a high class of origin. If social mobility is related to health and/or risk indicators for ill-health, such mobility might contribute to persisting health inequalities,3,6–8 and result in larger social inequalities in health in egalitarian than in less egalitarian countries. Several studies have shown that unfavourable living-conditions, poor mental health and negative life-style factors in adolescence, such as smoking, high alcohol consumption and low physical activity, are related to low future social position,9–12 as well as mortality.13–16
In the light of this background we attempt to investigate the contribution of risk indicators for mortality established in childhood or adolescence, and social mobility associated with such risk indicators, to relative socio-economic differences in mortality in adulthood.
For this study we used extensive data collected at compulsory conscription for military training in 1969/1970 among Swedish men born 1949–1951, and census data on socio-economic position from the years 1960 and 1985.
The purposes of this study are to investigate the extent to which the process of allocating people to socio-economic positions is related to the individual risk indicators for mortality present when entering adult working life, and to assess the importance of risk indicator-associated intergenerational social mobility in this process. Nine previously detected risk indicators for mortality in this study were used.16,17 We examine the distribution of several individual risk indicators for mortality among young men when entering adult employment (at ages 18–20 years), and estimate the importance of these risk indicators for later differences in mortality between socio-economic groups among the same men at 35–50 years of age.
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Study population
The study is based on data from a nationwide survey of 49 323 Swedish males, born 1949–1951, who were conscripted for compulsory military service in 1969/1970. Only 2–3% of Swedish young men were exempted from conscription at that time, in most cases due to severe handicaps or congenital disorders. Our study participants encompassed 97.7% of all conscripts in 1969/1970; the remaining 2.3% were born before 1949. The background to the Swedish conscription surveys and the variables they include have been presented in detail elsewhere.16,17 Nine variables from examination at conscription were selected for inclusion in the analyses, all on the grounds that they were previously known risk indicators for mortality, based on previous analysis of this same material.16,17
Assessments made at conscription included self-administered questionnaires focusing on social background, behaviour and adjustment, psychological factors, health, and substance use, such as alcohol consumption and tobacco smoking. The variable ‘contact with police and child welfare authorities (at least once)’ indicated problem behaviour. The conscripts were asked whether they, at least sometimes, had been on medication for nervous problems, and an affirmative answer was used as another measure of psychological distress.
A composite variable, ‘risk use of alcohol’, was based on the reporting of (at least) one of the following indicators of problem drinking: consumption of at least 250 g 100% alcohol/week, having taken an eye-opener for a hangover, having been apprehended for drunkenness and having often been drunk.
Subjects who smoked five cigarettes/day or more were regarded as smokers. Those shorter than 171 cm was considered as having a low body height. Those who attended 9 years or less of schooling were considered as having a low education. During the conscription examination the subjects were asked to report spells of unemployment before conscription lasting for at least 3 months. All the conscripts were seen by a psychologist for a structured interview and assessment of ‘emotional control’ (a summary assessment of mental stability, emotional maturity, and tolerance of stress and frustration was obtained) on five levels. Persons at levels 1 or 2, jointly forming the lowest 20%, were regarded as ‘exposed’. Conscripts reporting or presenting psychiatric symptoms were seen by a psychiatrist, and any psychiatric diagnosis was also recorded according to the International Classification of Diseases 8.
Data on socio-economic position
Information on the socio-economic position of destination of each conscript was based on infromation on occupation and obtained by linkage between records from the conscription survey and the National Population and Housing Census of 1985. Through information on personal identification numbers, parents and children were linked to each other between censuses. Information on father's socio-economic position, also based on occupation, was obtained from the National Population and Housing Census of 1960, i.e. when the subjects were 9–11 years old. Census data are held by Statistics Sweden, and there were census response rates of 98% in 1985 and 99% in 1960. All subjects were classified into manual workers and non-manual employees for childhood and adult position, respectively, forming four groups [stable as manual worker (manual worker as class of origin/manual worker as class of destination), upwardly mobile (manual/non-manual), downwardly mobile (non-manual/manual) and stable as non-manual worker (non-manual/non-manual)]. In all, 33 374 men were available for classification into these four groups. Of fathers, 10.5% did not report an occupation in the 1960 census, and 9.8% were farmers. Of the subjects themselves, 14.7% did not report an occupation for the 1985 census, and 2.3% were farmers. Farmers were excluded since it was not possible to establish how they compared hieararchically with manual workers and non-manual employees, respectively, and to decide on mobility status.18
Mortality
By means of personal identification number, further record linkage was effected to the National Causes of Death Register 1986–1999, held at Sweden's National Board of Health and Welfare.
Data analysis
For each mobility group in 1985 the proportion of men with a risk indicator, as reported in the conscription survey of 1969/1970, was computed.
The association between the four mobility groups in 1985 and mortality 1986–1999 was calculated in both a univariate and a multivariate model using the logistic procedure in the SAS statistical package. The same procedure was used for the comparison between manual and non-manual groups based on childhood and adult position, respectively. Odds ratios (ORs) were used as approximations of relative risks (RRs). In the multivariate models the RR associated with being in a particular mobility group in 1985 was estimated, controlling for the effect of the risk indicators measured in the conscription survey. RRs, as well as proportions with risk indicators, are presented by mobility category. Computations were based on the 31 332 conscripts who contributed full information concerning all the variables included in the study.
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Early-established risk indicators for mobility-associated mortality
Within the cohort, 7761 workers were classified as stable non-manual, 7859 as upwardly mobile, 3139 as downwardly mobile and 12 573 as stable manual.
On almost all variables the proportions with risk indicators were highest among stable manual workers and lowest among stable non-manual employees. Proportions were largely similar between persons downwardly mobile and stable as manual workers, and also similar between those upwardly mobile and stable as non-manual employees (table 1).
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Mortality risk in different social mobility groups
Between 1986 and 1999, 612 men had died (cardiovascular disease 125 cases, external causes 234 cases, whereof 139 suicides). Considerable differences in mortality risk were found between manual workers and non-manual employees, but there was almost exactly the same RR for stable manual workers and those downwardly mobile. Stable non-manual employees and those upwardly mobile showed similar low risks (table 2).
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In multivariate analyses, including all the variables presented in table 2, differences in RRs of mortality between the mobility groups were considerably reduced. Around 57% and 47% of the original increase in RR was explained among stable manual and downwardly mobile workers, respectively (table 2).
Childhood socio-economic position, adult socio-economic position and mortality
There were mortality differences between manual workers and non-manual employees as defined by the socio-economic group of their father at age 9–11 years (i.e. childhood position). When outcomes were measured on the basis of adult socio-economic group at age 34–36 years (as reported in the 1985 census), the differences were considerably greater (table 3, univariate). In the comparisons between manual and non-manual workers, RRs fell considerably for both childhood and adulthood socio-economic position on controlling for the set of risk indicators (table 3, multivariate 1). We also conducted analyses where we compared manual workers and non-manual employees and where both positions were simultaneously adjusted for each other. The RR fell considerably for manual worker as childhood position when adjusting for adult socio-economic position, while manual worker as adult socio-economic position were not affected at all by adjustment for childhood position (table 3, multivariate 2).
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Discussion |
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This study is the first to systematically examine the contribution of risk indicator-related intergenerational social mobility to social inequalities in mortality, and the first study which shows that such mobility may explain a substantial part of socio-economic differences in mortality.
The dataset employed has several advantages for the study of intergenerational health-related social mobility. Data on social class of origin are based on information from fathers themselves (when subjects were 9–11 years of age) rather than on retrospective information, which has been used in most studies of this issue. Data on personal characteristics in late adolescence were collected at the time of labour market entry and were partly based on standardized tests performed by trained investigators.
A weakness of the study is that, due to its reliance on conscription survey data, only men were included. Furthermore, owing to missing information on socio-economic position of origin in the 1960 census or achieved socio-economic position in the 1985 census, and also because a father or a subject was categorized as other than a manual or a non-manual worker, 32% of the cohort could not be allocated to a mobility group. Moreover, the RRs, and also the proportions with risk indicators, presented for the various socio-economic groups were calculated on the basis solely of the individuals for whom there was full information on all the variables included in the multivariate models. However, the proportion of subjects with a risk indicator among those with an adult position as manual worker or non-manual employee and whose childhood position was farmer (the most common reason for exclusion from the study) was not different from the included individuals with an adult position as manual worker or non-manual employee, respectively. We only used two socio-economic groups, manual and non-manual, and it could be suggested that the shift from a manual position to a low non-manual position could be a short step. However, the results in table 2 did not change when individuals holding lower non-manual positions were excluded.
In survey investigations, considerable under-reporting of alcohol consumption is likely, and under-reporting is assumed to occur in proportion to actual consumption level.19 In other studies of Swedish military conscripts, it has been concluded that self-reported data on alcohol consumption are valid for epidemiological analysis.20,21 Although the other risk indicators used in this study are also subject to misclassification, all the factors employed are related to adult mortality.16,17
The size of the contribution to inequalities in adult mortality made by health-related social mobility may depend on the frequency of mobility in a society.7 If the relationship between health and social mobility is as in the current study, an increase in the mobility rate would increase socio-economic differences. In Sweden, social structure was not as stable, and the homogeneity of classes in terms of social origin not as pronounced as in Britain during the period of study.22,23 Furthermore, during the 1970s and 1980s, the barrier between manual and non-manual classes became easier to surmount across generations in Sweden, and for the age group considered in this study there is a strong relation between education and social achievement.24
Some authors have, based on empirical findings, suggested that social mobility, even when health related, moderates or constrains social differences in health.25 Others have shown both empirically and theoretically that social mobility may both increase or constrain social inequalities in health.26 In a study by Power et al.27 based on the British 1958 birth cohort, socio-economic differences in height decreased as a result of intergenerational mobility, while in our study socio-economic differences in height increased as a result of intergenerational mobility.
Socio-economic differences in mortality in adult populations have previously been reported to be wider when determined from achieved than from childhood socio-economic position. It has also been observed that mobile groups have a similar mortality risk as the group they enter.18,28–30 Such relations have often been interpreted as a result of circumstances in the adult environment. However, Vågerö and Leon29 suggested that mobile groups might have been brought up under different circumstances from those of non-mobile groups from the same class. This interpretation is in accordance with results presented by Illsley6,31 based on data from Scotland during the 1950s. He found that women who married men of a higher social position than their fathers were taller and more educated, and had a more favourable pregnancy outcome, than others of the same socio-economic position of origin or those who were downwardly mobile from a higher social position. Such an interpretation is also in accordance with the findings in our study. In table 3 (multivariate model 2) are shown the results of analysing childhood position and adult position together in the same model. The increased RR for adult position was not affected by control for childhood position, while the smaller increased RR for childhood position was entirely explained by control for adult position. However, when we controlled the effects of adult socio-economic position for risk indicators for mortality established in late adolescence, those risk indicators accounted for more than 50% of the increased relative risk among manual workers. Hence, the suggestion that the mobile groups were brought up under different circumstances from those of the non-mobile groups from the same class of origin29 and that childhood and adolescent risk indicators for mortality contributes substantially to socio-economic differences in mortality for this age group is supported strongly by our results. By using information on health-related factors collected at labour market entry we could show that early established risk indicators for mortality were strongly related to mobility and could explain a substantial part of the increased mortality among manual workers compared with non-manual employees based on adult position.
Some adverse circumstances in early life seem to have importance for school achievement, lifestyle and mental well being in late adolescence, and to be linked to a less privileged adult life with regard to work environment and other living conditions. In our study, such adverse conditions in early life were clearly not well reflected by the father's socio-economic position. Instead it seems that boys with fathers in manual positions who were to become non-manual employees themselves grew up under circumstances, in terms of the risk indicators studied, that resembled the circumstances of the boys who had fathers in non-manual positions and were to become non-manual employees themselves. Similarly, those boys who had fathers who were non-manual workers and who were to become manual workers themselves grew up under circumstances that, concerning risk indicators, resembled those of boys whose fathers were manual workers and who were to become manual workers themselves.
Over the last few years there has been an increased interest in life-course determinants of health in adulthood.32–34 Individuals following divergent social trajectories are exposed to different health risks throughout life, and accumulate a different health burden over their life course. The findings of this study suggest that several risk indicators for mortality in early adult life have their origin in childhood circumstances. Other causes of death become relatively more common after the age of 50 years and the impact from social mobility could look different in older age groups.
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Conclusions |
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Several risk indicators for early mortality were found in excess among 18- to 20-year-old men who were to be recruited into manual occupations. This was true regardless of whether their fathers had a manual or a non-manual position. Proportions with risk indicators were lower among men who entered non-manual positions regardless of socio-economic position of origin.
The results suggest that a substantial part of the socio-economic differences in mortality among young men in Sweden during the final decades of the 20th century had their origin in childhood circumstances and were, at least partly, the result of social mobility related to poor mental well-being and an unfavourable lifestyle established in childhood and adolescence.
Key points
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Acknowledgments |
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This study was financed by the Swedish Council for Working Life and Social Research (project No. 2001-1057).
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