Effort–reward imbalance model and self-reported health: cross-sectional and prospective findings from the GAZEL cohort
Introduction
Psychosocial factors at work have been found to have adverse effects on health. In most epidemiological studies, the job strain model (Karasek, 1979; Karasek & Theorell, 1990) has been used to evaluate the dimensions of psychological demands, decision latitude, and social support. An other model, the effort–reward imbalance (ERI) model, is becoming more and more widely used (Siegrist, 1996). This model is based on the notion of reciprocity of efforts spent and rewards received underlying the typical work contract. However, failed reciprocity (‘high cost/low gain’) is not uncommon under certain labour market conditions and may elicit strong negative emotions and stressful experience. Moreover, ERI is likely to be experienced more intensively by employees who are characterized by a specific style of coping with demands and rewards, overcommitment. Overcommitted people underestimate the demands at work and overestimate their own capacities. In the long run, they run the risk of experiencing reward frustration and exhaustion. In summary, the ERI model defines three psychosocial dimensions at work: effort, reward and overcommitment, and it postulates that a combination of high effort and low reward (ERI) could lead to adverse health effects. In addition to these two work-related dimensions overcommitment at work acts as a personal risk factor. Separate and combined effects of these dimensions on health are postulated.
The factors defined by the ERI model have been found to be important contributors to health, especially cardiovascular disease (Bosma, Peter, Siegrist, & Marmot, 1998; Niedhammer & Siegrist, 1998; Siegrist, Peter, Junge, Cremer, & Seidel, 1990; Siegrist, Peter, Motz, & Strauer, 1992), and cardiovascular risk factors, such as hypertension, atherogenic lipids, and fibrinogen (Peter et al., 1998; Siegrist, Matschinger, Cremer, & Seidel, 1988; Siegrist, Peter, Cremer, & Seidel, 1997; Siegrist, Peter, Georg, Cremer, & Seidel, 1991). Various studies also showed that these aspects of work were associated with other health outcomes, such as sickness absence (Peter & Siegrist, 1997), poor well-being (de Jonge, Bosma, Peter, & Siegrist, 2000), and reported symptoms (Peter, GeiBler, & Siegrist, 1998).
Some recent studies dealt with the relationships of psychosocial factors at work to health status or health-related quality of life, and either self-reported health or the Short-Form 36 questionnaire (a generic health status measurement instrument) was used as health outcome (Amick et al., 1998; Borg, Kristensen, & Burr, 2000; Cheng, Kawachi, Coakley, Schwartz, & Colditz, 2000; Lerner, Levine, Malspeis, & D’Agostino, 1994; Pikhart et al., 2001; Schrijvers, van de Mheen, Stronks, & Mackenbach, 1998; Stansfeld, Bosma, Hemingway, & Marmot, 1998). Part of them had a prospective design (Borg et al., 2000; Cheng et al., 2000; Stansfeld et al., 1998). As reported by Zapf, Dormann, and Frese (1996) most of the literature on stressors and health is cross-sectional, and the weaknesses of this design are widely acknowledged, because it usually makes the demonstration of causal relationships impossible. All these studies used the job strain model, except one cross-sectional study (Pikhart et al., 2001) and a prospective one (Stansfeld et al., 1998) which explored the ERI model. The cross-sectional study by Pikhart et al. (Pikhart et al., 2001) showed a significant association between ERI and poor self-rated health. In the 5-year prospective study by Stansfeld et al. (1998), ERI was a predictor of a decline in several dimensions of health functioning.
Self-reported health (or alternatively self-rated, self-assessed or self-perceived health) has been studied intensively over the last decade. This parameter has several advantages for epidemiological research. It constitutes a general single-item question to which the answers can easily be collected via a self-administered questionnaire. It reflects a person's integrated perception of health and is known to take into account the various aspects of health, as suggested by the World Health Organization's definition of health, which includes its physical, mental, and social aspects. Several authors have reported strong associations between self-reported health and more objective measures of morbidity (Kaplan et al., 1996; Miilunpalo, Vuori, Oja, Pasanen, & Urponen, 1997; Moller, Kristensen, & Hollnagel, 1996). Further, in prospective studies, poor self-reported health was found to be a significant predictor of mortality (Idler & Benyamini, 1997; Kaplan et al., 1996; McGee, Liao, Cao, & Cooper, 1999; Miilunpalo et al., 1997; Wannamethee & Shaper, 1991).
The objective of the present study was to explore the associations between psychosocial factors at work, measured with the full-recommended version of the ERI model, and self-reported health, using alternative formulations of this model. The data collected underwent cross-sectional and prospective analyses, whose results were then compared. As the study population included a large sample of workers, men and women were studied separately to explore potential gender-specific associations.
Section snippets
Study population
The GAZEL cohort was established in 1989 and originally included 20 624 subjects working at Electricité De France–Gaz De France (EDF–GDF), comprising men aged 40–50 and women aged 35–50 at baseline (Goldberg et al., 2001). Since 1989, this cohort has been followed up by means of yearly self-administered questionnaires and by data collection from the company's personnel and medical departments. Research on psychosocial factors at work and health has been conducted in this cohort since 1995 (
Study population
In 1998, 14 641 subjects in the GAZEL cohort answered the self-administered questionnaire, i.e. 72.7% of the 20 147 subjects asked to complete it (477 of the 20 624 subjects in the initial cohort were not sent a questionnaire in 1998, because 447 had died and 30 had been lost to follow-up). Of the 14 641 respondents, 10 175 (69.5%) were working in 1998, 4254 (29.1%) had retired, 159 (1.1%) were not working because of long illness or disability, 35 (0.2%) were not working for other reasons (unpaid
Discussion
Our findings underline the differences between the respective results of the cross-sectional and prospective analyses for the relationships between psychosocial factors at work and self-reported health. The cross-sectional analysis showed that ERI and overcommitment were significant risk factors for self-reported health for men and women. All formulations of ERI provided the same results. The study of effort and reward separately showed that reward was significantly associated with
Acknowledgements
The authors’ thanks go to the members of the GAZEL study team, especially to Marcel Goldberg and Annette Leclerc, to the Medical Committee of EDF–GDF, and to all the participating workers of the GAZEL cohort, who made the study possible.
The collaborative research presented in this paper was supported by the ESF programme on Social Variations in Health Expectancy in Europe.
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