Occupational stress and hypertension

Article Outline

• Abstract
• Introduction
• Discussion
  • Methodologies
  • Confounding Variables
  • Difficulties in Assessing the Job Stress Interaction
  • Measurement
• Conclusions
• Acknowledgment
• References
• Copyright

Abstract 

Occupational stress, or job strain, resulting from a lack of balance between job demands and job control, is considered one of the frequent factors in the etiology of hypertension in modern society. Stress, with its multifactorial causes, is complex and difficult to analyze at the physiological and psychosocial levels. The possible relation between job strain and blood pressure levels has been extensively studied, but the literature is replete with conflicting results regarding the relationship between the two. Further analysis of this relationship, including the many facets of job strain, may lead to operative proposals at the individual and public health levels designed to reduce the effects on health and well-being. In this article, we review the literature on the subject, discussing the various methodologies, confounding variables, and suggested approaches for a healthier work environment.

Keywords: Blood pressure, hypertension, job strain, occupational stress

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Introduction 

Cardiovascular disease (CVD), and hypertension as one of its major components, is a major cause of morbidity and mortality in modern society. The physiological parameters of these diseases have been extensively studied and reported, as have some of the psychosociological factors that interact with them. Among the many causative factors, mental stress or strain is believed to be a prime culprit. The mental, emotional, and social demands engendering anxiety and stress in the modern world are constantly increasing, and numerous efforts have been made to analyze them in an attempt to minimize their effect. Some of the most common environmental stressors are found in the work situation.¹, ², ³, ⁴

Occupational strain or stress is considered, in one of the models, to result from a combination of high demands with low decision latitude in the workplace, and there is vast evidence linking it with blood pressure (BP) elevation and CVD. The demands of the workplace comprise both job- and human-related variables. Job-related variables include work schedules (shift work or irregular hours, rotating schedules), time pressures, machine-paced work, repetitive-routine or monotonous activities; physical conditions such as heat, noise, lighting, sedentary or active tasks; contact with the public; solitary or interactive tasks; and controllable or uncontrollable tasks. They also involve hierarchical status, involving different degrees of responsibility, decision authority and latitude, and prestige. Stress may also stem from problematic relationships with co-workers or superiors, such as conflicts or unfair treatment, ambiguous or contradictory work demands, and role overload or understimulation although support from colleagues or supervisors may alleviate their effects on stress.

Human variables that impact on stress are job satisfaction, the organization of the work, and whether the job offers security and flexibility, recognition and reward, and possibilities for advancement. Personal variables, such as self-perceived capabilities, self-confidence, and the ability to cope with stressful situations, also come into play. Indeed, it has been suggested that the perception that one’s job is stressful² or the perception of control over events¹ may be powerful predictors of elevated BP.

A number of intermediate variables whose effect can probably not be isolated from that of occupational stress add to the complexity of the problem: “direct mechanisms” (through physiological variables) and “indirect mechanisms” (through behavioral risk factors).⁵ The extent of BP variation in daily life may also be influenced by cognitive processes dependent on cultural background and emotional state.⁶ Some of these are unchanging and individual, such as gender, race, or ethnic group; indeed, there is evidence that these are key variables that lead people into jobs with more or less occupational stress in the first place. Other cognitive processes are of a social or psychological character and will or may change over time: age, job status, marital status and harmony,⁷, ⁸ coping mechanisms, anger expression and control, personality, lifestyle, socioeconomic factors, education, and social support.³, ⁹, ¹⁰

Some or all of these variables have been extensively studied and discussed in the literature relating job strain to CVDs, hypertension in particular. Still other studies provided little or no evidence of the direct relationship between job strain and BP levels.¹¹, ¹², ¹³, ¹⁴

The methods for studying this relationship are almost as numerous as the variables themselves, and introduce additional complexity to the nature and magnitude of the problem. These include the different ways BP can be measured (ambulatory, one-off or followed up, episodic or regular, during working hours, or 24-hour), and its relationship to the activity of the sympathetic nervous system. Job characteristics are typically assessed once only, which may result in misclassification. Conversely, attempts to assess job characteristics over a working life are hampered by methodological problems associated with survey length and content, and retirement from the workplace.¹⁵

Other methodological factors that may confuse the issue are use of different questionnaires (complexity, content and length, applied or self-administered), different scales for measuring job strain, cross-country comparisons, cross-occupational differences, and choice of study population (for example, borderline hypertensives, or known hypertensives vs. normal/high risk).

Attempts at “objective assessment” have spawned countless studies, some of which are listed in Table 1. These studies have yielded conflicting conclusions, inconsistencies related to differences in study design (case control, prospective), composition of the study population (single gender or mixed, ethnic grouping), the instruments for measuring job stress (job-related or individual-oriented), and/or outcome measures.¹⁶, ¹⁷, ¹⁸, ¹⁹ Some reviewers have suggested that because the stressful aspects of work assessed by the different questionnaires are not identical, theoretical models could be combined when planning organizational or public interventions to reduce job strain.⁴, ¹⁷

Table 1. Blood pressure and job strain studies

AI, augmentation index; ABPM, ambulatory blood pressure monitor; ATC, air traffic controllers; baPWV, brachial-ankle pulse wave velocity; BELSTRESS, Belgian Job Stress Project; BMI, body mass index; BP, blood pressure; BPM, blood pressure monitor; CHD, congestive heart disease; CV, cardiovascular; CVE, cardiovascular event; ECG, electrocardiogram; HANES, Health and Nutrition Examination Survey; HAPIEE, health, alcohol and psychosocial factors in eastern Europe; HDL, high-density lipoprotein; HR, heart rate; JCQ, Job Content Questionnaire; NHANES, National Health and Nutrition Examination Survey; PAMELA, Pressioni Arteriose Monitorate E Loro Associazioni; SBP, systolic BP; WHQ, Work History Questionnaire; WOLF, Work Organization, Lipids, and Fibrinogen.

Various approaches have been suggested in an attempt to arrive at consensus about the possible relationship between occupational stress and hypertension with a view toward formulating preventive or compensatory interventions. While being conscious of the near impossibility of the task of reaching valid or operative therapeutic conclusions, some practical suggestions have been made.¹⁸, ¹⁹, ²⁰, ²¹ Approaches to the reduction of stress at the work site are addressed at the end of this article.

The subject has been reviewed in the medical and sociopsychological literature. The present review focuses on the problematic aspects of the subject, including the different models for measuring and assessing effects, varying time spans, outcome variables, and delineation of the biosocial parameters studied. Table 1 complements the text with a number of key studies, selected mainly because they deal with specific aspects or special populations of workers. The studies were selected by a search of PubMed for reviews using the words job (or work) strain (or stress) and BP (or hypertension) during the past 10 years, and examination of some of their references.

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Discussion 

Methodologies 

Some studies of the possible association between job stress and cardiovascular risk factors, especially hypertension, deal with work-related stressors alone or in conjunction with individual characteristics, whereas others concentrate on individual differences in response rather than on the nature of the stressors. Because occupational demands, threats, and conflicts—the most frequent stressors—cannot be identified by direct physical or biological measurement, theoretical concepts, and integrative models have been developed to delineate stressful job characteristics.²¹ A number of questionnaires have been created to enable evaluations and comparisons, including Landsbergis’ Work History Questionnaire (based on the Job Demands-Control-Support model),¹⁵ Karasek’s Job Content Questionnaire (JCQ),²² Cesana’s Mopsy questionnaire (modified JCQ),²³ and Siegrist’s Effort-Reward Imbalance (ERI)²⁴ The two most frequently used approaches are the JCQ,²² which defines job strain as a two-dimensional construct composed of a high level of psychological demand and a low level of perceived control or decision latitude, and the ERI model, which gauges the effect of stressful experience at work on the incidence of diseases such as CVD.²⁴ The ERI model has been used less widely than the JCQ for assessing job stress. Although the JCQ model focuses on workplace characteristics, the ERI model is concerned with the stressful features of the work experience and their possible relationship to CVDs. Each of these approaches gives a different insight into the problem. When the two questionnaires were compared, the full JCQ, which is mostly used in CVD studies in the United States, Europe, and Japan was found to contain questions covering most of the relevant job strain variables, many more than the ERI.²⁵

Large portions of the workforce in modern economies are exposed to mental and emotional demands and threats at work, and as a result psychosocial stressors are becoming more frequent.

The effect of the psychosocial stressors on CVD “is likely to parallel or even outweigh the contribution of the more traditional occupational stressors (physical and chemical hazards).”²¹ Psychological or psychosocial stress appears to result from the interaction between environmental demands and environmental control (or rewards).

Choi et al²⁶ studied the role of psychosocial work characteristics (job control and psychological demands, both separately and together) on the amount of leisure time physical activity (LTPA), and found that active LTPA was more prevalent in workers in low-strain jobs. They suggested that the cumulative stress of high-strain jobs could inhibit workers from engaging in LTPA, with obvious deleterious effects on their health. However, longer working hours (or shift work or a second job) and low annual income may be additional deterrents to leisure time activities.

Chronic stressors may not be life-threatening initially, and their effect depends on human decision making and coping strategies. The primary stressors, which are environmental, interact with the individual’s psychological makeup to produce the perception of the level of stress.² The magnitude of the response is determined by the interaction of three factors: the degree of arousal in the central nervous system engendered by the stimulus, the individual’s ability to cope with the stressor, and the physiological susceptibility of the individual. These have been dubbed ‘the three Ss’: stressors (stimulus), stress (subjective element), and sickness (the physiological response).²⁷ Still another approach proposes a tripartite approach defining the relationship between job strain and BP: environmental stressors, psychological (personality/susceptibility/previous experience), and physiological/biological factors.³ Beilin¹⁰ explored the paradigm relating environmental psychosocial stress, individual coping mechanisms, and lifestyle-related factors such as obesity, alcohol consumption, and sodium and potassium intake to BP levels. He considered these issues critical for research methodology in this area, because previous studies had shown conflicting results.

In a meta-analysis of five US databases assessing the relationship between psychosocial dimensions of work and coronary heart disease risk factors, the findings were not as strong as expected; this might be explained by the use of casual BP in those studies.²⁸ There were no consistent results across either risk factors or databases, although there was some evidence that the degree of decision latitude at work was related to risk factors. It has been suggested that different individuals working in jobs with similar duties may perceive these duties differently, and may have various degrees of success in coping.

Confounding Variables 

Some of the confounding variables are sociological, relating to changes in gender and ethnic or cultural group roles, whereas others depend on technological advances, increasing educational levels, urbanization, and the like. Outside the family, the occupational setting is believed to be one of the most important potential environmental stressors in modern society. Siegrist’s model²⁹ suggests that the lack of balance between efforts spent at work and rewards—money, promotion prospects, job security, and self-esteem—can elicit stressful responses. Psychosocial experiences outside of work, at home and in the community, and across the lifespan may be significant enough to be taken as part of the psychosocial analytical framework, even when workplace effects are the primary focus.²⁹

Evidence suggests that the mechanism involving elevated BP is substantial for both women and men.³⁰, ³¹ Curtis et al found that although job strain was more prevalent among women, they did not consider it a predictive factor for elevated BP; this again could be explained by casual BP being the method of measurement.³² On the other hand, the increased activity of the cardiovascular and sympathoadrenal medullary system caused by a stressful work environment in women, emphasizes the role of gender. This may be modified, however, by the woman’s domestic role, length of employment, and job demands.³³ In a study of white collar women with a university degree, family responsibilities combined with high job strain were found to have a greater effect on BP than either of the two variables alone.³⁴ Other researchers found an association between job constraints and hypertension in both genders, although it was particularly noticeable in women.³⁵

A study of female nurses in Holland reported that the strong effect of job stress on BP reported in studies of men was less prominent in women.¹³ The absence of effect on ambulatory blood pressure monitor (ABPM) or heart rate of job strain alone or in conjunction with social support variability raised the question whether the gender differences were due to psychological or physiological differences (effects of menopausal status, sensitivity to catecholamines and cortisol in target organs, social gender roles, and attitudes in social situations). It was suggested that in a homogeneous work setting, differences in job strain are due to subjectively experienced job demands and decision latitude, rather than objective job characteristics.

Although female participation in the labor force has increased, home and family roles and responsibilities have not always kept pace.³⁶ On the one hand, working mothers are protected from the negative aspects of being full-time homemakers and dependent on a male partner, thus increasing their self-esteem; on the other hand, employment outside the home places many competing demands on them, resulting in fatigue and role strain. Occupational prestige and personal income (as opposed to familial) are sometimes offset in women by conflicting responsibilities, and may have adverse effects on clinical parameters such as BP, diabetes, and body mass index (BMI).¹² In Pickering and Devereux’s ² analysis of the potential sources of domestic stress related to BP, married women had higher systolic BP at work, whereas married women with children had higher systolic and diastolic BPs both at home and at work. The main source of stress in single women was at work, and they showed patterns of BP similar to men. Marital cohesion may interact with job strain in affecting BP levels, strengthening or weakening the effect in accordance with the degree of cohesion or lack of it.⁸

Stress or strain, which may manifest itself as depression or exhaustion,¹² can be due to overstimulation or understimulation.³⁶ Eaker¹² distinguished between occupational situations with high demands and a high level of control, and situations with high demands and a low level of control, both of which may be stressful. Pickering and Devereux² considered that the specificity of the JCQ model is both its strength and its weakness. Although it ignores certain individual-related factors, conceptualizes “control” rather narrowly, and concentrates on the work situation (the environment), its strength lies in directing attention to the potential negative effects of high-strain jobs, independent of worker characteristics that might moderate these effects. The demand/control approach treats emotional response as a dependent variable, derived from work-related behavioral requirements, and not isolated from them. Thus, the assessment of an effect must include not only an evaluation of the job demands, but also how effectively they can be controlled.

The hierarchical status of the worker at the workplace probably affects both the perception of stress and the ability to cope with it. One may suppose that a job with a high degree of mutual support between coworkers will be less stressful than one involving strain and conflict with colleagues at the same or a different (higher or lower) hierarchical level. A person with managerial status has a great deal of authority, but the accompanying responsibility may affect the stress response. In other words, although the “stress of higher status” hypothesis may be relevant for both men and women, the rewards of higher status may be offset by greater stress.³⁷ Conversely, a person lower down on the hierarchy may not have to face the responsibility that comes with rank, but conflicts with superiors because of unfair treatment or demands or insufficient reward may engender anger and depression leading to stress.³⁸ Peter and Siegrist³⁹ found that middle managers, characterized by simultaneous high effort and low rewards (active coping), were at a greater risk of developing hypertension than those with low reward alone (passive coping).

Intra-occupational studies may have a strong subjective component, related perhaps to personal status within the hierarchy, whereas inter-occupational studies provide a more objective assessment by the individual.⁴⁰

It is important to remember that lower socioeconomic status is associated with higher levels of BP and CVD risk, and must be taken into account when assessing how various stressors may affect cardiovascular health.⁴¹ Moreover, the association between stress and chronic disease may depend on social class to such an extent that the effects cannot be separated.¹⁶ They can be measured and analyzed separately or together in relation to BP.⁴²

In addition, new work patterns involving computer-based and network communications, and mass media communication serving as a means of social coordination in ever-increasing numbers and types of social activities, may require new methodologies for assessing the psychosocial work experience.⁴³

Difficulties in Assessing the Job Stress Interaction 

The problem with all these ostensibly valid conclusions lies in the enormous difficulty of assessing and quantifying the two principal variables: job and stress. Differences in the three main components of all the studies that make evaluating and comparing them difficult are the population of the study, the time span studied, and the methods of measuring occupational stress. In order for statistically valid conclusions to be drawn aimed at effective preventive or therapeutic solutions, the scientific method requires a unified approach.

Study populations are vastly different. Some investigators examine a specific type of occupation: physicians,⁴⁴, ⁴⁵ air traffic controllers,⁴⁶ nurses,¹⁹, ⁴⁷ bus drivers,¹⁶, ¹⁹, ⁴⁸, ⁴⁹, ⁵⁰, ⁵¹, ⁵² teachers,⁵³, ⁵⁴ blue collar workers,⁵⁵, ⁵⁶ white collar workers,⁵⁷ prison guards,⁵⁸, ⁵⁹ and government employees.⁶⁰ Others try to compare different occupational sectors.⁶¹ Some studies focus on one gender only, such as women teachers and/or nurses,¹³, ³³, ⁶², ⁶³ women managers,⁶⁴ white collar women,³⁴, ⁶⁵ male civil servants,⁶⁶ male cabin crew and teachers,⁶⁷ and others study inter-gender differences.³⁵, ³⁸, ⁴⁷, ⁶⁸, ⁶⁹ Some studies deal with the population of one country, whereas others attempt cross-country comparisons. This might be the reason that some studies provided little or no evidence to support the belief that job strain is directly related to blood pressure levels.

Bus drivers are considered a special worker population, with jobs characterized by complex tasks requiring rapid response to unexpected hazards that have to be performed under a rigid time schedule, frequent shift work, a high level of responsibility for passengers and equipment, and a low level of control discretion over how to carry out the job.⁴⁸ Indeed, professional drivers, particularly urban transport operators, were the workers with the most consistent evidence of increased risk of ischemic heart disease and hypertension in a review of 34 studies.⁷⁰ These workers, exposed to a wide range of psychological and physical stressors, may be prone to higher rates of hypertension than other blue collar workers, irrespective of perceived stress. It is important to remember that occupational stressors can affect BP even if they are not perceived as stressful.⁷¹ Gobel et al assessed job strain in different types of bus drivers and buses in different cities, using electrocardiogram measurements and eye movement analysis.⁴⁹ They found that short-haul bus drivers were exposed to a particular work load situation: high-density traffic and frequent stops, often involving simultaneous execution of tasks, performed with compulsory body posture and under exposure to vibration and noise. Rydstedt¹⁹ expressed this situation as the contradictory demands made on bus drivers: safety vs. adherence to timetables, repetitive and sedentary work balanced against vigilance and the processing of a multitude of signals, with little or no control over the pace of work and schedules. These various studies point up the difficulty in drawing conclusions from studies with variations in methodology and outcome measures.⁴⁸

Irritability, fatigue, sleep disturbances, and low back pain are frequently reported among pilots.⁷² High demands were associated with sleep problems among captains, and long-haul flights were associated with sleep problems among first officers. Low skill discretion was associated with fewer sleep problems among first officers.⁷³

Firefighters, police officers, and other emergency responders, including ambulance drivers, were also grouped together as having specific characteristics.²⁰ It was suggested that strenuous duties interacted with personal risk profiles to affect BP in this group. In addition to the fatigue and sleep disruption induced by the irregular hours they are required to work, they have higher rates of chronic disease and mortality.⁷⁴ This type of work is characterized by long periods of relative inactivity punctuated by unpredictable and stressful bursts of high intensity and potentially life-threatening activities. However, here, too, a “healthy worker effect” comes into play, because emergency responders are subjected to medical and physical exclusion criteria at job entry. Sega et al found that BP was not increased in air traffic controllers, for instance, but they suggested that because this was a highly selected group with suitable training, they could more adequately cope with stress.⁴⁶ A “healthy worker effect” was also thought to be partly responsible for mediating the adverse effects of shift work on cardiovascular risk factors and hypertension.⁷⁵

The time spans of the studies differ. Some measure BP once or over a short period of days, whereas others are longitudinal or prospective.⁷⁶, ⁷⁷ The latter are valuable in assessing the physiological or psychological effect of sustained stress, but when the interval between measurements is long, both the study population and the work conditions may have changed.¹ Dropout of “highly stressed” participants from studies may be a much greater problem than previously assumed.²⁹

In a prospective study of psychosocial factors and ABPM, Landsbergis et al introduced a Work History Questionnaire to try to gauge the health effects of past jobs over time, cautioning that one cannot disregard the changes in an individual’s self-perception as well as other family and environmental changes occurring during that period.² Assessment of job characteristics over a working life can be informative about the health effects of historical job characteristics, which often change over time; but, such studies entail asking numerous questions about each job, increasing the survey length and potentially reducing response rates, to say nothing of the failures of memory recall when dealing with an employment history that spans several decades. In another prospective study on the effect of cumulative job strain on systolic BP among men, the risk was comparable in magnitude to that of age and sedentary behavior, unrelated to occupational stress.⁶⁵ When longitudinal studies are performed, the recognized seasonal fluctuations in BP should also be considered, a point ignored in most studies.

Measurement 

The parameters and scales used for measuring stress⁷⁸ or occupational stress as well as the modes of measurement differ from one study to another. It is almost as difficult to delineate the end points for measurement of BP as it is to determine arbitrarily the cutoff points defining high-strain jobs, especially as stress is generally dependent on the individual’s self-perception.⁴⁰ Karasek’s JCQ model uses a self-administered questionnaire consisting of a maximum of 49 questions to measure the social and psychological characteristics of jobs and their effect on the individual; these include decision latitude, skill discretion, social support, physical demands, and job insecurity. The model presumes that psychosocial experiences are a major determinant of health and well-being, mediated by neurophysiological mechanisms as well as behavioral pathways.

Many studies are short-term, whereas some are longitudinal,⁷⁶, ⁷⁷, ⁷⁹ and it has been suggested that information about chronic life stress exposure and the average daily load (eg, job strain) may be more useful than the effect of laboratory stressors (cold pressor test, active coping mental stressors) for gauging the effect on subsequent BP levels.⁸⁰ Because laboratory stressors are modulated by genetic and environmental factors, high daily life stress augments the BP effects of family history and baseline stress responses. Thus, the group of participants expressing both genetic susceptibility and higher stress reactivity is at greatest risk of elevated BP or other cardiovascular problems; in other words, the adverse effects of increased life stress or decreased stress buffers would be most pronounced among individuals who are high stress responders as well as genetically susceptible. These authors⁸⁰ proposed a new hypothesis, the Genetic and Environmentally Modified Stress Responsivity Hypothesis, for gauging the interactive and additive effects of the three critical factors—increased daily life stress/decreased buffers, high stress responsivity, and genetic susceptibility—rather than examining environmental stress factors in isolation.

At the physiological level, chronic exposure to stress is believed to be one of the most prominent environmental causes of hypertension.² Clearly, the genetic makeup of the individual and a family history of hypertension are crucial factors in the relationship, but even the physiological mechanism by which stress may affect BP is not fully understood. Although it is generally accepted that neural and hormonal mechanisms are of major importance in the early stages of elevated BP, structural changes in vessel wall may cause it to be maintained through the sympathetic nervous system, by delayed effects of adrenalin and other physiological changes.⁸¹ Moreover, different factors act differently to cause hypertension in different individuals. Family history and genetic predisposition may interact with a number of environmental factors including occupational stress to cause hypertension,⁸⁰ although insufficient attention has been paid to this important aspect of the problem.

Some researchers studied the effect of job strain on specific physiological variables causing sleep disturbances and hypertension (chronic endocrine and cortisol levels and sympathetic activity),¹⁷, ⁸¹, ⁸² as distinct from the effect of other environmental factors (lifestyle, diet, alcohol) on those same variables.⁶¹ Others used cardiovascular risk factors as the starting point and examined their effects on the perceived job stress,⁴⁷ emphasizing the weakness of one-time measurements compared with 24-hour monitoring. Schnall et al⁷⁶ found that job strain might cause long-term structural changes in the heart, as shown by increased left ventricular mass index.

Even evaluating the nature and mechanism of the stress response is considered problematic.¹² Is it dependent on the pituitary-adrenocortical system (qualitative), or is it measured in terms of the sympathetic-adrenal medullary system (SAM quantitative), reflecting the intensity of stress arousal? Although the biological mechanisms linking psychosocial work stress to ill health are not fully understood, a plausible biological linking mechanism could be the catecholamine and cortisol reactions observed during stressful conditions.¹⁷, ¹⁹, ⁴⁷, ⁸² Peter et al¹⁹ found that increased mean cholesterol values were associated with increased degrees of extrinsic effort/reward imbalance, thus supporting the hypothesis that effort/reward imbalance as a stressful experience at work could be related to cardiovascular risk. Maina et al¹⁷ obtained different results for measures of salivary cortisol output in relation to job strain assessed by the JCQ and the ERI models. It has been suggested that combining the results of the two models might give a better picture of psychobiological correlations of the work environment,⁴, ¹⁷ and perhaps this applies to the physiological variables as well.

Genetics and culture are also considered factors in the job-stress relationship. The results of a number of studies conducted on Japanese and other Far Eastern populations ⁵⁵, ⁸³, ⁸⁴ have been consistent with the findings in most Western studies. Japan even has a term for death from overwork—karoshi—and considers that overtime work burdens the cardiovascular system of white collar workers.⁸⁵, ⁸⁶

Other studies however, did not support them, and even pointed to an inverse relationship between job strain and hypertension, suggesting that genetic or cultural characteristics may be important factors in the effect of stress as a causative factor in hypertension in these populations.⁸⁷ Karasek et al⁹ claimed that inter-occupational differences in job characteristics present an important reference standard for assessing the relative importance of country differences. However, while pointing out that there are national differences in income distribution as well as in work-organizational structures and family stressors in different countries, the averages of job demands, job control, and job social support are similar across countries despite cultural differences and differences in income distributions. In some cross-country comparisons, effort/reward imbalance at work combined with overcommitment was found to be associated with poor self-related health in all countries, but not to the same extent. The effects in Eastern Europe were not systematically comparable to those in the West,⁸⁸ although it has been suggested that the psychological job characteristics may be more similar across national boundaries than across occupations.²⁹, ⁸⁹ When studying one geographical area across jobs, Schlussel et al⁹⁰ compared seven different worksites in one city and concluded that worksite and job characteristics were important predictors of BP differences in different groups.

In relation to evaluation scales and objectivity, some studies using Karasek’s JCQ model found a relationship with ABPM levels, whereas other studies using more “subjective” measures of occupational stress found no such relationship, or even an inverse association. On this point, Peter et al⁴⁷ argued that the concepts “psychological job demands” and “decision latitude” are theoretically considered to be “objective” characteristics of the work environment. But, they pointed out, there are currently no established models for measuring these parameters in an “objective” fashion. The workers’ response may be influenced not only by the work environment, but by individual characteristics of the worker and life stresses, thus misclassifying the response to stress. Nevertheless, occupational stressors can be measured more objectively by methods that do not rely primarily on individuals’ perceptions of stress; these methods have also shown associations with cardiovascular outcomes. An example is the averaging of job characteristics scores across job titles.⁹¹, ⁹²

On a technical point, Choi et al⁹³ compared the differential item functioning of 27 JCQ items in six languages and found that half the items may be associated with differences in translation: skill discretion and decision authority tended to be underestimated in some versions, as were the psychological demands and variations in estimation of worker support. These factors should be considered when comparing results between countries.

The method by which BP is measured may also affect the results of long-term studies. It is of importance especially in light of the finding that mean ambulatory systolic BP is higher during work than during nonwork, this is one of the key findings supporting the hypothesis that work is playing an important role in elevation of BP. It is reasonable to suppose that one-time in-office measurements will not be representative, and vastly different in their implications, compared with 24-hour ABPM, which includes hours spent at home and at night.⁷⁷, ⁹⁴ Even then, can one assume that 24-hour measurements will be constant over a period of days? Literature dealing with job strain and stress sometimes ignores the fact that most secondary hypertensives are nondippers, making relating nondipping at to job stress misleading.⁹⁵

Casual clinic BP measurements are considered to be less reliable than 24-hour BP measurements, for reasons of observer error, white coat effect, and the known variability in a person’s BP (one particular study is an exception⁶⁵). This may account for why most studies of job stressors that use casual clinic BP measurements show no significant relationship between work exposures and BP, whereas such a relationship is found when ABPM measurements are used. Not only is ABPM a more reliable measure than casual BP, it also ties BP changes to mood and psychological state, gives a picture of dynamic BP fluctuations throughout the day and night, and enables comparisons between work and home, and wake and sleep. ABPM measurements have led to the definitions of people with normal clinical BP but elevated awake ABPM as having “masked” or “occult” or “hidden” hypertension.⁹⁶

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Conclusions 

In view of the enormous amount of evidence pointing to a relationship between job stress and hypertension, attention should now be focused on the practical health implications of the evidence, and on operative solutions and interventions to balance or minimize the relationship.

It has been suggested that the formulations defining job strain, decision latitude, and demands could influence the results: adding organizational influence to the task-level decision latitude variables invariably produced a stronger association between hypertension and job strain.⁹⁷ Lindquist et al’s finding⁹⁸ that work stress per se had no direct effect on BP levels prompted them to propose that individual coping strategies and lifestyles should be targeted as much as the work environment when formulating workplace health promotion programs. It has also been suggested that job satisfaction, with all its correlates, should be measured as an organizational level outcome because theoretically based interventions depend on organizational changes beyond the employees’ abilities to perform.⁵ In one example of interventional measures aimed at reducing occupational stress in bus drivers, self-reported health complaints did not decrease after the intervention, nor did perceived effort and work-related fatigue.¹⁹ However, the intervention, admittedly on a small sample of drivers, allowed more control and reduced conflict between service and schedules.

Kales et al²⁰ proposed two approaches: making population-based wellness strategies available, such as encouraging aerobic exercises, weight control, sleep hygiene, stress management; screening and individual counseling for individuals at higher risk of hypertension and prehypertension; and time-limited work clearance to ensure that hypertensives do not continue to work indefinitely with uncontrolled BP, by providing incentives to stabilize BP or restricting duties.

Siegrist²¹ proposed that specific employment groups at elevated risk of stress be identified and preventive efforts developed. In addition, theory-guided interventions could be implemented and evaluated within single companies and organizations at the individual level (reduction of commitment), the interpersonal level (improvement of leadership, providing esteem rewards), and the structural or organizational level (compensatory wage systems, gain-sharing, non-monetary gratifications). Lucini⁹⁹ reported reduction of job strain when an anti-stress program was introduced at the workplace that reversed autonomic symptoms. Others have emphasized the importance of managers stating clear goals, objectives and lines of authority, in addition to providing proper training for the workers.²⁵ Rosenthal et al¹⁰⁰ reported a method of relaxation based on slow breathing exercises that reduces BP—a potentially useful tool at the work site and at home.

Finally, national and international regulations that ensure and enhance healthy work, fair employment contracts, and welfare measures could be promulgated. Such joint efforts would reduce a significant part of the burden of CVDs. They would go far toward implementing the declaration of the International Labour Organization that “decent work involves opportunities for work that is productive and delivers a fair income, security in the workplace and social protection for families, better prospects for personal development and social integration, freedom for people to express their concerns, organize and participate in the decisions that affect their lives, and equality of opportunity and treatment for all women and men.”

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Acknowledgment 

We thank Dr. Jenni Tsafrir for her editorial work and significant input.

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References 

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