Occupational Health Research Paper

Health is not only the absence of illness. It is also a positive state in its own right. Most of the research that has been published, however, regarding work and health has been devoted to the establishment of relationships between certain adverse working conditions and illness. Accordingly most of the paper will be on work–illness relationships. But we shall also discuss possible pathways between good working conditions and the promotion of health.

An important basis for our understanding of the effects of working conditions on health has been the physiological stress research which was initiated by Hans Selye (1976). Initially stress researchers were studying acute reactions to energy demanding situations. During later years, they have examined the biological consequences of long-lasting adverse life situations.

2. The Physiological Basis Of The Effects Of Work On Health

Genetic evolution and selection processes are slow. Therefore our biological reactions to stressful situations are likely to be approximately the same as they used to be several thousand years ago. It has been emphasized by many authors (Levi 1972, Frankenhaeuser 1980) that this may not be functional for man in modern societies. It was functional to become strong, courageous, and insensitive to physical pain for a human being that faced dangerous animals. Such situations are uncommon for the modern human. Instead, most of the contemperous dangers have to do with complicated social interactions, and in such situations physical energy mobilization is not functional.

3. Energy Mobilization And Anabolism At Work

In Selye’s (1976) general adaptation syndrome, ‘stress’ was seen as the general reaction to a nonspecific challenge or adverse condition. The situation that induced stress was labeled a stressor (factor which induces stress). Since this has central importance to the understanding of stress at work, a short description of the energy mobilization will be given here. The most important biological process is the provision of energy—glucose and free fatty acids enter the blood, and these are used for the immediate production of energy. But there are several parallel phenomena, all of which aid the body in the physical fight or flight. Examples are lowered excretion of water and salt, decreased sensitivity to pain, and decreased inflammatory responses to infections. Since energy mobilization (resulting in elevated blood concentration of glucose and free fatty acid) has the highest priority, anabolism (restorative and regenerative activities in the cells) is down regulated. Anabolism is central to the body’s central defense of all the organ systems that need constant rebuilding and restoration. If this goes on for a long time (several months) increased sensitivity to physical and psychological stress in bodily organs is the ultimate result.

Another consequence of long-lasting demands for energy mobilization is that the endocrine systems may change their regulatory patterns. This means that the ability of the body to stop energy mobilization when it is no longer needed may be disturbed or that the counter-regulation (inhibition of energy mobilization) is inhibited. Most processes in the body have a counter-regulatory mechanism that operates in order to inhibit a process that has been stimulated.

4. Physiological Short-And Long-Term Adaptation To Requirements At Work

The hypothalamo–pituitary–adrenocortical system (HPA axis) is of central importance to the biological arousal mechanism. The steroid hormone cortisol which is released from the adrenal cortex is the most extensively studied ‘agent’ in this system. Cortisol facilitates biological arousal in most organ systems. Disturbed regulation of the HPA axis has been described as a possible consequence of long-lasting arousal. There are at least three kinds of such regulatory disturbances in the HPA axis, all of which are of relevance to health at work:

(a) Lack of inhibition of arousal. All reactions in the body evoke counter-regulatory reactions. This is true also of energy mobilization which should stop when the threat disappears. Normally cortisol inhibits higher centers in the HPA axis when it has been in the aroused state for some time. When this inhibition does not take place in the normal way, the levels tend to become constantly elevated.

(b) Lack of response to stimulation of the HPA axis. This means that plasma cortisol levels are low and that the normal activation does not take place when the HPA axis is stimulated artificially.

(c) Unstable levels. In this kind of disturbance the plasma cortisol levels may be low at rest, but certain situations—that are specific to the individual and have to do with the symbolic significance of the event— trigger a strong HPA axis reaction that may seem to be out of proportion to the importance of the trigger. This occurs in subjects who have been exposed to extraordinarily stressful situations, such as torture, war, disasters, and incest.

The first kind of regulatory disorder, (a), is typical of Cushing’s syndrome (overproduction of corticosteroids including cortisol due to a disease in the adrenal cortex) and could be one alternative regulatory disturbance in psychiatric depression. Psychiatric depression is mostly associated with constantly high cortisol levels although in most cases, however, the circadian rhythm is preserved (Rubin et al. 1987)

The second kind, (b), has been shown to exist in a subgroup of patients with the diagnosis chronic fatigue syndrome or CFS (Demitrack et al. 1991). Since at least one other group of patients, those with fibromyalgia (a disorder characterized by easily fatigued muscles which are painful when fatigued), share some symptoms that are typical of this regulatory disorder with CFS patients, it is possible that part of the myalgia problem is that they also suffer from this kind of disturbance.

The third kind, (c), of regulatory disorder is found in post-traumatic stress disorder (PTSD) (Charney et al. 1993). The key element in the etiology of PTSD seems to be that the long-lasting extreme arousal level increases the number of cortisol receptors on the cell surfaces and also increases their sensitivity. Since the sensitivity is so high, only low concentrations of cortisol are needed to keep the system working at rest. This may be the reason why low serum cortisol levels are found at rest in patients with PTSD.

5. Unemployment And Stress

Unemployment is a common phenomenon in all industrialized countries. In most European countries it is presently of the order of 10 percent. Research has tried to establish to what extent unemployment contributes to poor health. At present there is agreement that poor health increases the risk of becoming unemployed in periods of financial crisis but there is also agreement that unemployment per se contributes to poor health. Longitudinal studies of subjects who have gone through the different stages of unemployment (Brenner and Levi 1987) or started activities again after a long period of unemployment have shown that several physiological systems are markedly affected by these processes.

For instance, there is an elevation of the secretion of cortisol (as an index of energy mobilization) and prolactin (which mirrors passiveness in a crisis situation). It is accordingly reasonable to assume that health could be affected. There is published research showing that long-lasting unemployment increases the risk of mental disorder (Hallsten 1998) and is also associated with a lifestyle that increases the risk of developing cardiovascular disease, particularly in young people (Janlert et al. 1991, Janlert and Hammarstrom 1991). Economic hardship may add to the health consequences (Vinokur et al. 1996). Jahoda (1979) formulated the basic reasons why work is such an important activity in modern life—the most central one being that work provides structure to life. There is extensive research showing that organized support can help the unemployed to regain employment (Vinokur et al. 1995). Evaluation of such programs, however, also shows that these programs may increase passiveness and feelings of low self-esteem if the initiative of the individual is taken away.

6. Combined Effects Of Physical And Psychosocial Adversities At Work

Extensive research has been devoted to the disentanglement of physical from psychological stress in studies of health and disease. For instance, in the study of the importance of ergonomic load to the development of musculoskeletal disorders, it has been considered important to adjust for psychological stress. Extensive epidemiological studies of large samples of subjects have shown that ergonomic load contributes to the development of musculoskeletal disorder but that psychosocial factors at work may also contribute significantly (Kilbom et al. 1996). Recent studies have shown that combinations of physical and psychosocial factors may be of particular importance (Vingard et al. in press).

It has been pointed out by several authors (House and Cottington 1986) that combinations of physically adverse (chemicals, radiation, physical load, infections) and psychosocial conditions may be of particular importance to health in a changing world. It is not possible to monitor all new chemicals that are used, and our psychosocial conditions are changing. Accordingly, analyses of interactions will be of increasing importance (Rantanen 1999)

It has been important for the study of relationships between working conditions and health to have theoretical models which form the basis for hypothesis testing. The interplay between the individual and the environment has been an important point of departure in all theoretical modeling in this field. Some of the models have focused on environmental, for instance, the demand–control model, and some on individual aspects, for instance, the eustress–distress model. The person–environment fit (PE fit) and the effort–reward imbalance models are examples of models which take the interaction between the individual and the environment into account. These four models will be described briefly below.

7. Theoretical Models For The Study Of Work And Health—Individual Or Environment

The individual’s response to demanding work situations has been the point of departure for Frankenhaeuser and her co-workers (Frankenhaeuser 1980) who introduced one of the most influential models, the eustress–distress model. According to this model, the individual responds to the work situation with different degrees of effort. The bodily reactions to a high degree of effort are influenced by the concomitant degree of joy or distress in the situation. High effort with joy is labeled eustress while high effort with marked distress corresponds to a negative stress reaction. Laboratory research indicated that joyless effort was associated with elevated catecholamine as well as elevated cortisol excretion, whereas the eustress situation was associated with increased catecholamine excretion but no elevation of cortisol excretion. The physiological damage associated with the negative reaction was assumed to be much worse than that of the eustress situation.

The environmental counterpart of the effort– distress model is the demand–control model which has been used extensively during later years. Accordingly this will be described in more detail. The demand– control model was introduced by Karasek. It is a two-dimensional synthesis of the demand (‘stress psychological’) and the ‘lack of control’ (sociological) research traditions (Karasek and Theorell 1990, Karasek 1979). It was assumed that the employee’s possibility to utilize and develop skills (skill utilization) was closely related to authority over decisions. Skill utilization has to do with the employee’s control over the use and development of his her skills, whereas authority over decisions has to do with the employee’s control over decision making relevant to his work tasks. The two factors have often been added to one another to constitute decision latitude.

The other dimension in the original demand— control model, psychological demands, includes qualitative as well as quantitative demands.

The high demand–low decision latitude combination, job strain, is regarded as the most dangerous for illness development. According to the theory, this kind of situation, if prolonged and repeated for a long time, increases sympathoadrenal arousal and at the same time decreases anabolism, the body’s ability to restore and repair tissues (Karasek and Theorell 1990).

The combination of high psychological demands and high decision latitude is defined as the active situation. In this situation, the worker has been given more resources to cope with high psychological demands because he/she can make relevant decisions, such as planning working hours according to his her own biological rhythm. In addition he/she gets good possibilities to improve coping strategies—facilitating feeling of mastery and control in unforeseen situations. This situation corresponds to psychological growth.

The low demand—high decision latitude situation—the relaxed one—is theoretically the ideal one, whereas the low demand–low decision latitude situation which is labeled passive may be associated with risk of loss of skills and to some extent psychological capacity.

It soon became evident that a third component was needed in the demand–control model—social support. This dimension had already been introduced previously in job stress research (House 1981), see below. Johnson has discussed this component extensively. He has pointed out that collective support may be difficult to separate theoretically from collective control. Workers who are exposed to adverse working conditions may join forces and increase their control over the working conditions. The worst hypothesized situation is iso-strain—job strain and lack of social support (Johnson et al. 1989).

There is a striking difference between the effort– distress model and the demand–control model. Whereas the former is designed to explain differences in individual response to stressors, the latter is designed to assess the environmental conditions, the stressors. There is of course a relationship between the models since eustress reactions are likely be more common in the active job situation and negative stress reactions more common in the job strain situation.

8. Interaction Between Individual And Environment

One of the most influential models has been that of the Michigan school (Katz and Kahn 1966). This theory postulates that adverse reactions at work arise when the person–environment fit is poor. In this model the interaction between a person’s characteristics and the environment is the central theme. If the characteristics of the job do not fit the characteristics of the person there is a high likelihood that negative stress reactions may arise. There is considerable empirical support for this hypothesis (Kahn 1981). Another important theme is the expectation of the person—those who have very positive expectations may be more disappointed than those who have negative expectations if the conditions do not fit. The Michigan school also added social support at work as a central theme (House 1981).

According to Siegrist (1996), a crucial job factor for health consequences is the degree to which the workers are rewarded for their efforts. When a high degree of effort does not meet a high degree of reward, emotional tensions arise and illness risk increases. The effort– reward imbalance model is described in another chapter by Siegrist in this book. It is basically a sociological theory that includes individual processes. The effort component includes individual (intrinsic effort, which is close to psychological demands in the demand–control model) as well as environmental aspects (extrinsic effort). The reward component includes three different aspects of reward, namely monetary reward, promotion possibilities, and self esteem.

During later years, considerable efforts have been made to explore the relationship between theoretical job stress models and ‘hard endpoints’ for health development. Previously the scientific literature was criticized because most of the relationships had been observed in studies which used self-reports both in descriptions of the stressors and the health outcomes (Kasl 1982). There may be a risk in such studies that a pattern of complaining may affect both explaining variables and health outcomes. Therefore, studies have included prospective designs as well as objective outcomes (such as myocardial infarction or cardiac death) and objective recordings of stressors at work (through population means for each occupation regarding decision latitude, for instance, or by means of expert ratings of the crucial stressors). The demand– control model has been more extensively studied than the other models.

9. Job Stress Models And Disease

The significance of the demand–control–support model to cardiovascular disease, in particular high blood pressure and myocardial infarction (Schnall et al. 1990, Theorell and Karasek 1996, Melamed et al. 1998), has been tested in many epidemiological studies. There is considerable support for the hypothesis that the combination of high demands and lack of control is associated with increased risk of developing a myocardial infarction before retirement age. There are limitations in the findings, however: the findings are stronger for blue-collar workers than for white-collar workers, more established for men than for women, and more pronounced before the age of 55 than after that age.

The control (decision latitude) dimension has had a more consistent relationship with myocardial infarction risk than the demand dimension. Loss of decision latitude has also been shown to be associated with increased risk of developing a first myocardial infarction in the near future, even after adjustment for other risk factors (Theorell et al. 1998). The support dimension has been less extensively studied than demand and control.

The findings are more convincing for myocardial infarction than for cardiovascular risk factors (Kristensen 1999). High blood pressure during activities has shown a convincing relationship with job strain, whereas high blood pressure at rest (measured in the doctor’s office) has not been associated with the demand–control model in any consistent way. Serum lipids and smoking patterns have not shown consistent relationships with job strain (Theorell et al. 1998). Accelerated blood coagulation may be a mechanism that operates in the relationship between job strain and myocardial infarction risk since recent studies have shown that high plasma fibrinogen is associated with low decision latitude (Tsutsumi et al. 1999, Brunner et al. 1996).

Variations over time in job strain have been shown to be associated with changes in endocrine parameters and immune system function of relevance to stress theory. For instance, in one study of men, plasma testosterone (which is important to anabolism) decreased and immunoglobulin G increased (indicating increased immune system activity) when job strain increased and vice versa (Theorell et al. 1990a, 1990b). In another study plasma testosterone increased when the total working life situation improved (Grossi et al. 1999).

Studies of the effort–reward model in relation to risk factors have shown that in men high blood pressure and atherogenic lipids are associated with poor reward in relation to high effort. The patterns of association are different for men and women (Peter et al. 1998, Siegrist 1996).

The PE fit model and related models have been used in studies of cardiovascular risk factors and positive findings have been reported (Cooper and Payne 1978). Sickness absence has been shown to be positively associated with high demands and low decision latitude (North et al. 1996). Musculoskeletal disorders such as low back pain and neck–shoulder pain have also been studied in relation to the demand–control model. The findings have been mixed. The relationships depend on the group and the kind of disorder studied. In some studies, social support at work is crucial whereas in others psychological demands or decision latitude may be important. When the associations between musculoskeletal disorder and psychosocial work environment are adjusted for physical load, the associations are often weakened. Among female workers, physical load and adverse psychosocial conditions are frequently correlated (Josephson et al. 1999).

10. Integration Of Effort–Reward Imbalance And Demand–Control

There is evidence (Bosma et al. 1998) that the decision latitude component of the demand–control model and the effort–reward imbalance model are contributing independently of one another to the prediction of episodes of coronary heart disease. This finding confirms that the models are related to different psychosocial mechanisms linking psychosocial working conditions to health outcome. The models have psychological demands (extrinsic effort) in common but control (decision latitude) and reward are clearly different. A logical step would be to combine the models. Even if resources (control and support) are optimal for the development of good coping strategies in a highly demanding situation, the employees will need reward for high effort, and hence balance between the components is needed.

Most of the relationships that have been observed in this field would be without significance in society if it were not possible to prove that it is possible to improve health by means of changes in working conditions. Accordingly, the literature on job interventions and their possible effects on health is of considerable importance.

11. Environmental And Individual Psychosocial Interventions At Work

Quality of working life experiments have been carried out since the early 1980s. They have been evaluated in terms of productivity but not frequently of health, and it has been shown that they have very often been associated with a lasting increase in productivity (Kopelman 1985). They have mostly been based on the theories outlined above, and two basic ideas have been to increase decision latitude and to improve social support. From an intervention perspective, decision latitude has two components, namely intellectual discretion—possibility for the worker to decide how his knowledge should be used and developed—and authority over decisions—which has to do with work democracy, how decisions are made, and how workers are informed about important decisions. Increase in intellectual discretion has been achieved by means of job enrichment or increased worker responsibility for the complete product.

Increase in decision authority has been achieved by means of job enlargement or flattened organization hierarchy. Increase in social support, finally, has been achieved by means of improved feedback and the formation of more cohesive work groups. During later years, both in North America and in Scandinavia, the starting of regular staff meetings for systematic discussion of important decisions regarding work routines and goals has been used as a tool for increased decision latitude and social support.

The theoretical models described above have also been used in efforts to prevent illness and to promote health. The occupational health care team has often been an important vehicle in Scandinavian job redesign (see for instance Wallin and Wright (1986). The occupational health care team has the possibility to work both with the structure of the company and individual workers. It has the possibility to carry out individual measurements of psychological and somatic health indicators and to monitor these through the change process. It has been the experience of health oriented job redesigners that the concomitant emphasis on structure and individuals is helpful both for individual motivation to follow health promotion advice (which is strengthened when workers discover that there is willingness in management to improve the structure) and for success in instituting structural change (which will benefit from engagement of the individuals and their health problems).

Even in Sweden with its long tradition of work redesign, very few studies have actually documented health consequences of this type of job intervention. Most of the published studies have been based on self-administered questionnaires. One study of cardiovascular risk factors (Orth-Gomer et al. 1994) showed that a similar program aiming at improved decision latitude and social support for the employees (which was evaluated in a controlled study) was followed by a reduced ratio of LDL HDL cholesterol (the ratio between harmful and protective cholesterol) in the experimental but not in the comparison group. As in all experiments of this kind, the design was not ‘clean’ in the sense that all other changes had been ruled out, but the findings could be interpreted to mean that job redesign aiming at improved social relationships and decision latitude could lead to decreased cardiovascular risk.

Psychosomatic symptoms, such as gastrointestinal symptoms, tiredness, and depression, reportedly decreased among employees in part of the Volvo company after a number of psychosocially oriented job changes had been instituted, such as role change in supervisors in the direction of more facilitation, less authoritarian leadership style, promotion of personal contact between customers and employees, and increased teamwork (Wallin and Wright 1986).

The redesign process has been described in many case studies. The health consequences of improved work organization, however, have been in scientific focus in few published studies. Experiences in all EU countries have recently been summarized (Kompier and Cooper 1999). Evaluations of systematic efforts to improve working conditions by means of increased decision latitude, support, and reward in order to improve health are more common in the Northern countries than in other countries.

12. Notes On Future Work

In an increasingly unstable labor market in the future, employment security will be less common and global competition will increase (Aronsson and Goransson 1999). The education level of all workers in the world will rise. If we use the basic concepts of demands, decision latitude (including both intellectual discretion and authority over decisions), social support, effort, and reward in order to describe possible scenarios for the future, we might hypothesize the following to occur.

Psychological demands will continue to rise, both because there is more cognitive demand (memorizing numbers, handling computers, etc.) and more emotional demands. Numbers of collaborative partners are rising because of the increasing specialization of work, and thus there will be an increasing likelihood of complicated emotional communication for everybody. Decision latitude is becoming polarized and this will continue in the future. Workers with a high level of education will have more and more decision latitude, whereas less favored groups will have periods of unemployment interrupted by periods of short employment. This will be a poor basis for developing decision latitude for low education workers. Studies in several countries have already shown that workers in temporary employment have a bad position in decision processes. There are indications from several countries that differences in health between favored and less favored workers will increase.

The basis for social support will change gradually since workers on all levels will rotate more frequently between worksites in different projects than previously. Employers will have a special responsibility for the organization of social support in worksites.

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