Associations of job strain and working overtime with adverse health behaviors and obesity: Evidence from the Whitehall II Study, Helsinki Health Study, and the Japanese Civil Servants Study
Introduction
Psychosocial job strain (Karasek, 1979) has been shown to be a major, independent cardiovascular risk factor (Belkic, Landsbergis, Schnall, & Baker, 2004). Health behaviors are also important determinants of these largely preventable chronic diseases (Ezzati et al., 2005, Hu et al., 2005). Working overtime is also related to health behaviors and health (Caruso, Hitchcock, Dick, Russo, & Schmit, 2004). However, associations of these working conditions with adverse health behaviors have not been thoroughly studied. Nevertheless, it has been suggested, that psychosocial factors including working conditions might shape health behaviors (Stansfeld & Marmot, 2002), and may partly explain inequalities in metabolic syndrome and cardiovascular disease by affecting employees' health behaviors (Chandola et al., 2006, Marmot and Theorell, 1988). This highlights the importance of deepening our understanding of how working conditions might relate to adverse health behaviors and subsequent obesity. International comparisons provide a wider perspective to study these associations, while also seeking to identify similarities or dissimilarities across national contexts thereby showing more valid results.
A pathway between psychosocial working conditions and adverse health behaviors has been suggested as a response to environmental challenges such as high job strain and overtime work that may culminate in behavioral modification (Bhui, 2002). Accordingly, it can be hypothesized that employees compensate for high psychosocial job strain and working overtime with adverse behaviors. First, job strain may increase the consumption of fatty and sweet foods (Oliver, Wardle, & Gibson, 2000), while intake of fruits, vegetables, fish and meat may be reduced (Oliver & Wardle, 1999), at least among susceptible individuals (Oliver et al., 2000, Wardle et al., 2000). High job strain and overtime work are also potential barriers to physical activity (Schneider & Becker, 2005). Additionally, chronic job strain could increase heavy drinking, prevent smokers from quitting, or induce quitters to relapse. Since smoking is assumed to ease stress, smokers are likely to smoke more under psychosocially strenuous work (Parrott, 1999). However, as smoking is initiated usually already in young adulthood (Paavola, Vartiainen, & Haukkala, 2004), the relationship between psychosocial working conditions and current smoking is likely to rather reflect smoking intensity or maintenance of the harmful habit (Green and Johnson, 1990, Johansson et al., 1991). While strenuous work is hypothesized to increase drinking, heavy drinking may in turn affect both perceptions about psychosocial working conditions and the actual work (Cargiulo, 2007, Zins et al., 1999). Additionally, suggested behavioral modifications might predispose employees to subsequent obesity. These hypotheses need, however, further clarification and examination. As a large number of employed people are continuously exposed to psychosocially strenuous working conditions for a substantial part of their active time, it is important to examine whether this has detrimental effects on health behaviors and obesity across different countries and among both genders.
In line with these suppositions about assumed theoretical pathways, earlier research has shown that job strain and its dimensions, i.e., job demands and job control have some, albeit limited and inconclusive, associations with health behaviors and body mass index (Hellerstedt and Jeffery, 1997, Kouvonen et al., 2007). Most previous studies have focused only on smoking (Green and Johnson, 1990, Kouvonen et al., 2005) or heavy drinking (Bobak et al., 2005, Kouvonen et al., 2005, van Loon et al., 2004). Physical activity has also received some attention (Kouvonen, Kivimäki, Elovainio, et al., 2005), but studies about food habits are especially scarce (Kawakami et al., 2006). Working overtime may, in turn, influence employees' health by causing strain or changing health behaviors (Caruso et al., 2004). However, we lack evidence linking working arrangements with several health behaviors. Moreover, these previous results are based on non-comparative studies, with usually a limited number of working conditions and health behaviors. Instead, previous international comparisons have focused on different outcomes, such as self-rated health, while examining working conditions and health behaviors as determinants (Singh-Manoux et al., 2006).
Thus, we sought to widen and corroborate the current understanding of the associations between psychosocial working conditions, adverse health behaviors and obesity by pooling comparable employee cohorts from Britain, Finland and Japan. More specifically, by conducting this international comparison, we aimed to identify both common associations across countries and cohort-specific variations. When undertaking the present study design, some clarifications about the cohorts and justification for the comparisons need to be pointed out. In general, it should be borne in mind that the included countries have different welfare regimes (Dahl et al., 2006). First, despite many similarities as Western European countries, Finland and Britain, nevertheless, differ with regard to labor markets, welfare provision, income inequalities, as well as social and family structures (Esping-Andersen, 1990, Smeeding and Gottschalk, 1999), which in turn may contribute to health behaviors. For instance, in Finland the government and the labor unions intervene with the labor market conditions which may possibly lead to smaller differences in working conditions. This may affect the associations of working conditions with health behaviors as well. Secondly, concerning Japan, more secure possibilities for a lifelong job as well as better pay and promotion prospects with increasing age may also affect health behaviors and thus distinguish Japanese employees from their Western European counterparts. While social, cultural, and worksite contexts are likely to add to the complexity of the associations, as has been speculated previously (Hellerstedt & Jeffery, 1997), the socio-cultural diversity also provides fruitful contrasts for comparisons (Markus & Kitayama, 2003). Furthermore, clear counterpoints between Japanese distant cultural features and Western European countries (Kitayama et al., 2004, Markus and Kitayama, 2003) enable us to produce a more comprehensive picture on the associations between psychosocial working conditions and behavioral risk factors. Since Japan is the only non-Western, highly industrialized and educationally advantaged nation, its usefulness in comparative studies has been previously acknowledged as well (Inaba et al., 2005). Thus, by comparing British and Finnish employees with their Japanese counterparts, our key aim is to be able to assess the significance of job strain and working overtime to adverse behaviors and obesity, which might mediate the previously well-established relationship between job characteristics and (cardiovascular) health (Belkic et al., 2004).
Section snippets
Data
We analyzed pooled cross-sectional data of employees from three countries: Britain, Finland and Japan. The data collection in Finland and Japan largely followed the protocol of the British Whitehall II Study (London). The data from these countries were collected separately, and harmonized for pooling and comparability purposes. In general, all the items were practically identical in the three cohorts except that information about physical activity was more exhaustive in Britain than in the two
Descriptive statistics
The mean age in London and Helsinki was 52 years, and in Japan 51 years in both genders (Table 1). In each country, more men than women were managers or administrators. More men than women were married in all the countries. High job strain was more prevalent in Helsinki than London and Japan, whereas working overtime was more common in London and Japan than Helsinki.
The prevalence of the outcome variables differed substantially by country and gender. Unhealthy food habits were found among a
Main findings
This study sought to examine associations of job strain and working time with unhealthy food habits, physical inactivity, heavy drinking, smoking and obesity among employee cohorts from Britain, Finland, and Japan using comparable data. The main overall finding is that associations of these working conditions with adverse health behaviors and obesity are rare and weak in each examined cohort. Nevertheless, some associations were found. Similarities and dissimilarities, as well as
Conclusions
Job strain and working overtime have some, albeit limited, associations with health behaviors. Moreover, the associations are mostly weak and rather inconsistent within and between the genders and cohorts. Thus, our results from three cohorts suggest only modest support for the hypothesis that the effect of job strain on employee health might be mediated through health behaviors or obesity. Longitudinal studies are needed to confirm the causal pathways between psychosocial working conditions,
Acknowledgment
The Whitehall II study has been supported by grants from the Medical Research Council; British Heart Foundation; Health and Safety Executive; Department of Health; National Heart Lung and Blood Institute (HL36310), US, NIH: National Institute on Aging (AG13196), US, NIH; Agency for Health Care Policy Research (HS06516); and the John D and Catherine T MacArthur Foundation Research Networks on Successful Midlife Development and Socio-economic Status and Health. MM is supported by an MRC Research
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