Objective characteristics of jobs affect blood pressure at work, after work and at night

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1 Objective characteristics of jobs affect blood pressure Running head: Objective characteristics of jobs affect blood pressure Objective characteristics of jobs affect blood pressure at work, after work and at night (chapter in Fahrenberg & Myrtek (Eds.). Ambulatory Assessment in Progress) Renate Rau University of Technology Dresden epartment of Work & Organizational Psychology

2 Objective characteristics of jobs affect blood pressure 2 Objective characteristics of jobs affect blood pressure at work, after work and at night Introduction Four years ago, we discussed methods and results of psychophysiological analysis of stress and strain in real life work situations (Rau & Richter, 996). Based on Hacker s (985, 986) action regulation theory we reported results of stress/strain analyses according to all components of sequential completeness which should be included in all work activities (Miller et al., 960; Hacker, 985; 994; 998; Volpert, 987; Frese & Zapf, 994). These components were goal setting, preparing and organizing the tasks, executing, and feedback. The strain analysis of the reported studies was related exclusively to the working time and thus to short-term effects of work load, such as fatigue, boredom, vigilance etc. The methodological framework of the analysis and assessment of such short term effects is defined in the ISO 0075 (International Organization for Standardization ISO 0075, 99; ISO , 994). The study of such short-term effects can only be a first step towards discovering possible effects of work stress on health. The aim for an enlargement of the stress/strain paradigm from short-term effects to long term effects was not achieved with our first studies reported 996 (Rau & Richter). However, study of the effects of work stress during the time after work including the night is necessary when the workplace is seen as a potential source of stressors that might contribute to the development of heart disease risk factors. Furthermore, the time between work and night has to be considered since within this time further strained or relaxing activities can be carried out by the subjects. Since methods for an ambulatory monitoring of psychophysiological data have been become available, a growing number of studies include cardiovascular changes over 24 hours including ordinary work, leisure and night time. However, up to now the major interest has only been the analysis psychophysiological changes during working. Whereas there is a growing interest in recovery processes during the night, the time between work and night has hardly been examined (see studies regarding the time after work and night, e.g. Theorell, Knox et al., 985; Theorell, Perski et al., 988; Lundberg et al., 992; Frankenhaeuser, 993; Theorell, Ahlberg-Hulten et al., 993; Landsbergis et al., 994; Pickering, 993; Rau, 998; Schnall et al., 998). The study of work-related determinants of coronary heart disease has been mostly influenced by the job demand/decision latitude model proposed by Karasek and co-workers (Karasek, 979; Karasek & Theorell, 990). Data reported by Theorell et al. (99), Pickering, Schnall et al. (99), Rau (996), Schnall et al. (998) and Belkic, Emdad & Theorell (998) indicate that sympathetic nervous activity may be increased during occupational stress. In their studies, occupational stress was evaluated as high job strain, which is a combination of high demands at work with low decision latitude or control. Considerable evidence exists linking the exposure to job strain to hypertension (e.g. Schnall et al., 990; Theorell, Ahlberg-Hulten et al., 993; van Egeren, 992; Pickering, 993; Schnall et al., 998, Peter & Siegrist, 2000; Rau et al., in press). In a prospective cohort study (Whitehall II) 6895 male and 343 female civil servants were tested during three phases between 985 and 993 (Bosma, Stansfeld & Marmot, 998). It was found that low job control (but not job demand or social support) increased the risk of coronary heart disease (angina pectoris, severe pain

3 Objective characteristics of jobs affect blood pressure 3 across the chest, ischemia). Both self-reported and independently (by personnel managers) assessed job control showed roughly similar associations with coronary heart disease. Data of the reported studies regarding job demand and job control were mainly based on subjective work analyses (such as JCQ, Karasek et al., 998). Therefore, some researchers have started to employ analytic technique to overcome self-report bias and obtain more objective measures of job characteristics (e.g. Pieper, LaCroix & Karasek, 989; Theorell et al., 99; Landsbergis et al., 994). The average scores of psychosocial work characteristics for a particular job title are used for individuals with that job title (Johnson et al., 990; DOT 979). For example the Swedish classification system (Johnson et al., 990) consists of the following three psychosocial work characteristics: psychological demands, control, and social support, as well as the two physical work characteristics: physical job demands, and hazardous work. One of the ideas of this system is that it gives the researcher the possibility of avoiding individual bias that could be influenced by personality. However, with the changes in work organization (e.g. flexibility of working time, lean production) and the development of new occupations, the use of occupational group-based classification systems is becoming increasingly problematic. The classification system is based upon the idea that an occupation does not change over time and that, for instance, all secretaries who have been working at least twenty years in that occupation and who are older than 45 years have the same level of job control and psychological demands. However, the national occupational averages may have changed substantially over the intervening period. Additionally, Schwartz, Pieper & Karasek (988) have already reported that a large within variance exists in job characteristics. Therefore, an alternative operationalization of job strain other than the occupational classification system is indicated. Before discussing alternative methods, changes in the world of work are represented, since these changes require the development and use of objective methods of analysis. Changes in the world of work During the last two decades we have observed rapid changes in work organization and work content, such as:! Psychomental work load has risen while bodily activity has decreased Therefore, musculoskeletal diseases constitute one of the modern threats to employees health (Levi, Sauter & Shimomitsu, 999). Several studies have shown that physically monotonous and repetitive work, but also psychosocial factors at the work place, are associated with musculoskeletal diseases (e.g. Moon & Sauter, 996; Lundberg, Dohns et al., 999; Sandsjö et al., 2000; Hägg, 2000). For monotonous and repetitive work, employees typically have hardly any influence and control over their work situation and seem to be exposed to higher levels of chronic stress (Sjøgaard, Lundberg & Kadefors, 2000). Lundberg et al. (994) found enhanced effects of a mental stressor on trapezius electromyogram when this stressor was combined with physical load.

4 Objective characteristics of jobs affect blood pressure 4! Increasing flexibility of work time, characterized on one hand by a shortening of work time to part time jobs and on the other hand by the increased use of overtime in organizations It is not surprising that the effect of overtime on health has been studied regarding cardiovascular risks (Starrin et al., 990; Uehata, 99, Harmar and Ilmarinen, 999), depression (e.g. Kawakami & Haratani, 999), non-insulin dependent diabetes mellitus (Kawakami et al., 999), disturbed cognitive functions (e.g. Proctor et al., 996) and fatigue (Schorr, 99) in a similar way to the work already done in stress research. Beside an increase of overtime work, there is also a shift towards contingent work arrangements. The traditional long-term contracts with an implicit understanding of ongoing employment are gradually disappearing (McLean Parks, Kidder & Gallgher, 998; Lewis & Cooper, 999; Levi, Sauter & Shimomitsu, 999). Because of the temporary character of their employment, temporary employees are generally expected to express less favorable job attitudes and less commitment to the organization (Pearce, 998). Often, they have little control over the termination, the duration and the content of their work (Beard & Edwards, 995). Low control, unpredictable work situation, roll ambiguity, uncertain personal income due to the temporary work can contribute to job strain, impaired well being and diseases (Martens et al., 999; Sverke, Gallagher & Hellgren, 2000). When contingent work is voluntarily chosen by employees themselves (e.g. for a better balancing of work and family roles), this can also have positive effects. More research is needed for evaluation of the different natures of contingent work.! The introduction of new systems of work organization like lean production, total quality management etc. which lead to major changes in work design Landsbergis, Cahill & Schnall (999) reviewed studies which examined the impact of new systems of work organization like Japanese production management/lean production on work content and job stress. Thirteen studies tested effects of lean production in the car industry. Lean production in the car industry is based on detailed standardization and short work cycles (about 60 seconds) and accompanied by high work intensity and low decision latitude and only a modest and/or temporary increase of decision authority and skill levels. Landsbergis, Cahill & Schnall (999) concluded that work in lean production systems can be considered to have high job strain. Additionally, lean production is designed to remove activities (e.g. walking space at work stations; walking time) and time (waiting time, slack time etc. up to seconds) or more generally to remove indirect work between subtasks that is not absolutely essential to production. Thus, employees do not have the possibility to carve out some time for buffering activities like rest, bodily activities or social activities.! use of information and communication technology (ICT) The use of ICT often leads to an increased work intensity during decreased time for a task, greater attentional demands, emotional loading interruptions and higher demands on the cognitive system as a result of increased processing of information (Roe, Zijlstra & Leonova, 996; Carayon & Zijlstra, 999). Furthermore, there is a tendency towards a reduction of resting periods by the reduction of subtasks that

5 Objective characteristics of jobs affect blood pressure 5 require low concentration. Resting periods are also reduced when task execution is controlled by the computer, e.g. when inputting information into forms. Immediately after one task is finished, the computer is ready to start the next task (Baitsch et al., 99).! Qualifications become obsolete during a vocational biography Therefore, life-time learning is required (Bergmann, 998). The best solution for such life-time learning is qualification by working. But with the introduction of new work organization systems like lean production, increases in skill levels are very modest (Landbergis, Cahill & Schall, 999). An additional problem in industrial societies is that people s abilities for life-time learning are reduced with the duration and frequency of unemployment (Bergmann, 996).! Under the headline of new work organization systems, the introduction of small group activities (e.g. total quality control, total quality management) which, in contrast to employers, has fewer or no positive effects for the employees, must also be discussed (Imai, 986). The question is here, whether group work is a result of the team concept or of workers collectivity. Workers collectivity means groups which are constructed by workers themselves to improve their social support at work. In contrast, the team concept is based on socially engineered groups that have been constructed to maximize productivity and to maintain managerially oriented norms and values (Johnson & Hall, 995). Thus, the team concept might encourage workers to treat each other as competitors rather than as coworkers. This increases the risk of social stress. When we look at the changes in the world of work, it is not surprisingly that employees today complain less about physical load, but rather about work-related psychical stress (Sauter et al., 999). Therefore, the analysis of work places that lead to psychical stress and in the longer term to job strain and an increased risk of disturbed well-being or the development of risk factors for diseases is not finished yet. However, inherent to the introduction of new systems of work organization is the change of work design. The question is, can we influence work design towards healthy work by considering the employer s aim of improved productivity, quality and profitability? This is a very complex question. To find first answers it should be examined whether there are objective methods of analysing and designing work places and whether these are suitable for the job demand/control model of Karasek (979). Confirmation to the job demand/control model is preferred because most studies done according to job strain are based on this model. Such confirmation would also allow us to examine whether the findings of a relationship between psychosocial work characteristics (as a rule analysed by questionnaires) and job strain can be confirmed by using an objective method of work analysis. Such a method is the Task Diagnostic Survey (Rudolph et al., 987; Hacker et al., 995) which is based on action regulation theory (Hacker, 985, 998). Job demands and decision latitudes across different work settings can be compared by means of this method, applied to each individual work place. In contrast to the occupational group-based classification system, the Task Diagnostic Survey allows the analysis and evaluation of specific workplaces, and thus the potential source

6 Objective characteristics of jobs affect blood pressure 6 of stressors. Ambulatory blood pressure monitoring in strain research The effects of the exposure to job strain can not only be examined during working time. If this exposure plays a role in the development of sustained hypertension, it should be possible to demonstrate that job strain can cause a rise in blood pressure not only during work but also during leisure time and at night. The examination of the relationship between job strain and blood pressure changes should be based on ambulatory blood pressure monitoring. This method has the advantage that there is no observer bias and the number of readings is greatly increased. Additionally, this method is more ecologically valid than casual measure of blood pressure since blood pressure is measured during a person's normal daily activities including work (Schnall, Landsbergis & Baker, 994). However, the reliability of ambulatory blood pressure can be less than that of casual measures when some conditions such as setting, body position and physical activity, external noise (that affect blood pressure taking) etc. are not controlled for (Pickering, 99; Käppler, 994; Schmidt & Jane, 996; Fahrenberg, 996; Fahrenberg & Myrtek, 200). In a study with 78 normotensive and borderline hypertensive men, it was shown that physical job demands affect the blood pressure even at times without any motor activation (Rau et al., in press). Hierarchical regression analyses yielded highly significant effects of physical job demands on blood pressure during work in sitting position and during the night in men (R 2 ranged between.05 and.08 for diastolic blood pressure and between.07 and.0 for systolic blood pressure). Studies analysing the effect of an exposure to high job strain on leisure-time and night time have come to different and partly contradictory results. Data reported by Theorell et al. (99), Pickering, Schnall et al. (99) and Fox, Dwyer & Ganster (993) indicate that sympathetic nervous system activity may increase at work with high job strain and remain elevated at night, thus hampering nocturnal rewind. In borderline hypertensives, Theorell et al. (99) did not find an association between exposure to job strain and systolic blood pressure, while diastolic blood pressure was elevated at work and during sleep in those with high job strain occupations. The effect of exposure to job strain on ambulatory blood pressure was investigated in a three-year follow-up study by Schnall et al. (998). Using 24 hour ambulatory blood pressure monitoring on two occasions 3 years apart, they found that the group having high job strain at both baseline and follow-up had higher systolic ( mmhg) and diastolic (7 mmhg) blood pressure at work and at home as compared to the group that did not have high job strain at either assessment. On the other hand, in longitudinal studies by Theorell, Knox, Svensson, and Waller (985), Theorell et al. (988) and Landsbergis et al. (994), high demands combined with a low decision-latitude (high job strain ) were associated with elevated ambulatory systolic blood pressure at work but not during leisure time. An explanation for the different results of the relationship between job strain and cardiovascular activity during the time after work might be the relatively undifferentiated use of the labels leisure time and time at home. The activities after work consist both of stressing activities and of passive relaxation. Therefore, the labels leisure time and time at home have to be explained in future studies. Additionally, there are only a few studies that consider the effect of the exposure to job strain on the ability to relax or the data

7 Objective characteristics of jobs affect blood pressure 7 about sleep quality beside the effect on cardiovascular changes at night. Since the prospective Rotterdam Civil Servant Study (van Diest & Appels, 994), it is known that patients who had a myocardial infarction report for the time before their infarct that they felt excess fatigue. These feelings were attributed to prolonged overwork by many patients. This corresponds with the results by Ertel et al. (2000). For so called hightech jobs they found a significant correlation between working hours per week and a disturbed relaxation ability. Ambulatory assessment of a working day - an empirical study The aim of the present study is to explore the effect of objectively measured exposure to job strain on the cardiovascular reactions at work, after work and during sleep following a working day. The following hypotheses were tested: H : H 2: The exposure to high job strain as compared with exposure to low job strain is associated with an increased cardiovascular activation at work, after work and a delayed cardiovascular recovery at night. Negative health consequences on sleep such as reduced relaxation ability and sleep disturbances are expected for employees who are exposed to high job strain. Method Subjects 7 women aged between 20 and 60 years were tested. The women were employed in white-collar jobs and included software engineers as well as employees in public services. In order to recruit them, contact with the leadership of the company and with the Betriebsrat (this is a committee of chosen agents who represent the interests of employees facing the leadership of the company) was necessary to get the permission for the study within the companies and during working time. Afterwards women were recruited through spoken presentations at the companies and written presentations by using the internal company systems. As a rule we recruited all women of a division within a department. All women were paid 50 DM for participating in the study. The sample was reduced because only women regularly working 40 hours per week with complete data from the ambulatory assessment were included in the statistical analyses. 05 women fulfilled both conditions. There was a further down sizing of the sample because of the classification according to the exposure to job strain. The method of classification is described in the next section. After that the sample will be described which was finally used in the statistical analyses. Objective task analysis The classification of the exposure to high versus low job strain was based on the

8 Objective characteristics of jobs affect blood pressure 8 quadrant model of Karasek (979). In the present study the operationalization of the job demands and job decision latitude that creates the risk of job strain was not based on dichotomizing self-reports of job demands and decision latitude, but on objectively measured work characteristics using the Task Diagnosis Survey (TDS: Hacker et al., 995). The TDS scales were rated by experts, one occupational psychologist and one or two colleagues of each subject. The Task Diagnosis Survey is based on Hacker's model of action regulation (Hacker, 985, 994). This survey consists of the following five work-related dimensions: S S S S S technological and organizational work characteristics (2 scales for temporal degrees of freedom, procedural degrees of freedom, quantity/quality-conflicts, work-related decision processes, feedback, partial activity, work cycle time, possibility of prediction, information about organization, information about results, etc.), work-related cooperation and communication (three scales for amount of cooperation, kind of cooperation, kind of communication), mental regulation requirements (one scale for the level of mental operations), learning potential (two scales for qualification application, requirement to learn new things), responsibility (two scales for responsibility for results, processes or people, and individual versus group responsibility for results). The evaluation of analysed work dimensions is supported by thresholds for each of the TDS scales. Thresholds are defined as the lowest scale value that should be met in order to avoid fatigue, stress, monotony, psychosomatic complaints, or losing skills. These lowest scale values are empirically tested values of the TDS. If all of the scalethresholds are linked, a profile will be visible. In the TDS, this profile is known as the minimal profile. In addition to the use of the TDS, women were asked about their regular working hours and about their overtime work (in hours per week). In this study, employees were classified as exposed to high job strain when the objective task analyses yielded scores of decision latitude and job demand below their threshold values defined by the TDS. In detail, the decision latitude was determined by the TDS scale procedural degrees of freedom. This scale measures the objective possibilities of determining the working procedures. When the procedure is fixed, i.e. an employee has no freedom to decide what is to do and how something is to be done, or to choose the sequence of working procedures, then the scale procedural degrees of freedom does not meet the threshold value and has to be evaluated as below the minimal profile. Job demands were determined by the TDS scale temporal degrees of freedom. This

9 Objective characteristics of jobs affect blood pressure 9 scale asks about employees possibility of planning the time for executing the subtasks within a day or within a week. Indirectly, this is a question of work intensity. When the time for each step is strongly limited and the technical-related phases of each step are short (ranged between three and a maximum of 30 minutes), the scale temporal degrees of freedom does not meet the threshold value and has to be evaluated as below the minimal profile. The question of overtime work provides additional information for the operationalization of job demand. Employees may tend to work longer, when time pressure occurs because the daily amount of work can not be executed during regular working hours. Therefore, women were additionally classified as exposed to high job strain, when the scores of the procedural degrees of freedom scale were below the minimal profile and excessive work was done, defined by doing overtime work. When the scores of the scales procedural degrees of freedom and temporal degrees of freedom are higher than the thresholds for the minimal profile and women do not work overtime, employees are classified as exposed to low job strain. Table Description of the Sample High Job Strain Low Job Strain No Exposure to High or Low Strain All Subjects n Subjects Working Full Time and having Complete Data n 7 a 4 a 47 N 3 05 Missing 4 b 2 Note. a subjects used in further analyses (N = 58); b missing because incomplete data (n = 4) or because subjects did not work regular time on the day of 24-hour assessment (n = 8) Women who were exposed to neither high nor to low job strain (n = 47) were not included in the statistical analyses. A total of 7 women were classified as exposed to high job strain and 4 women were classified as exposed to low job strain. The sample which is used in the statistical analysis consists of 58 women (see Table ). Chi-squared analyses and t - tests were conducted comparing women exposed to high job strain and women exposed to low job strain on a number of demographic measures. The two job strain groups did not significantly differ on age, bodymass index or number of children (see Table 2). However, the number of smokers tended to be higher in the low strain group [n = 2 (29.3%), non-smokers, n = 29 (70.7%)] compared with the number of smokers in the high strain group [n = (5.9%); non-smokers, n = 6 (94.%)], χ 2 (58) = 3.78, p <.0. Table 2 Age, Bodymass-Index (BMI), Number of Children based on the Exposure to Low and High Strain Jobs

10 Objective characteristics of jobs affect blood pressure 0 Job Strain Low (n =4) High (n = 7) Age M SD t (58) = ns BMI M SD t (58) =.52 ns Children a no one more than one χ 2 2 (46) = 4.53 ns Note. a 2 women did not answer the question for children Ten of the 58 women were on anti-hypertensive medication (five in the low and five in the high strain group). A chi-squared analysis was performed to examine hypertensive and normotensive status as a function of the exposure to low and high job strain. Analysis revealed no significant difference [χ 2 (58) = 2.50, ns]. The women who were hypertensives or on anti-hypertensive medication were excluded from all statistical analyses of physiological data. Procedure All women were tested during 24 hours on a normal working day. Women performed their regular work for eight hours, with leisure time in the afternoon and the evening, and then they slept. Women arrived at the laboratory which was set up in the companies between 7 and 8 am. The ambulatory equipment was put on and then they were given instructions for blood pressure reading (keep the arm as motionless as possible) and for answering the diary questions on the handheld computer (see next section). After the whole procedure, which took around 5 minutes, women were dismissed. After the 24 hours of ambulatory assessment, women returned to the laboratory again. The physiological data and the handheld computer data were transferred to the laboratory computer. Based on this data, women were questioned about their activities, special emotions and stress they experienced within the last 24 hours. The whole procedure took 30 minutes in the laboratory. Women were asked to complete questionnaires regarding sociodemographic data, relaxation ability and sleep disturbances. Relaxation ability was assessed using the

11 Objective characteristics of jobs affect blood pressure FABA-questionnaire (Richter et al., 996). In this questionaire critical values are defined to identify subjects with a disturbed relaxation ability. The critical values differ depending on gender and age (younger group: < 30 years, middle-aged group: years, older group: > 50 years). Sleep disturbances were evaluated using the Sleep Wake Experience List (van Diest, 990), which asks the women for their sleep experiences during the last three months. This questionnaire also defined critical values for each dimension (e.g. falling asleep, waking up during the night etc), and for the general diagnosis of a sleep disturbance. These critical values are independent of gender and age. Recording of setting and variables of introspection Before the day of ambulatory assessment, task analysis and an interview about normal daily activities were carried out in order to define specific individual programs for questions of the setting on the handheld computers. Women were asked about their regular activities at work and at home as well as about people they are usually in contact with. Handheld computers (PSION 3a) were used as computer diaries. Women kept these computer diaries to record their location (e.g. at work, at home, in the garden etc.), body position (standing, sitting, lying), and activities (an individual checklist was presented with the activities which had been identified during preinterview, e.g. reading, repairing something, doing the housework etc.) during the whole day until going to bed. In addition, Women repeatedly answered questions concerning perceived control, perceived stress and moods. The control and the stress dimension were rated on seven-point scales from not at all to completely. Positive and negative affect ratings were used for indicating mood. The items for positive and negative affect were drawn from the PA/NA-model by Schallberger & Pfister (in press). This instrument is based on a 2-factor model of affect which is similar to that of Watson and Tellegen (985). Questions for affects were bipolar and were rated on seven-point scales from -3' (e.g., sad) to +3 (e.g., very happy). The questions on the handheld computer had to be answered hourly by the women over the whole 24 hour period with the exception of the night. Women were called to answer the questions by the computer s alarm-beep. Recording of blood pressure Blood pressure readings were taken by the Korotkoff-method using ambulatory monitoring systems (BOSO TM2420). A microphone was placed over the arteria brachialis of the left arm under the blood pressure cuff. The blood pressure monitor was programmed to take blood pressure every 5 minutes throughout the day and every 60 minutes throughout the night. A shorter interval of blood pressure taking during night would be disturbing for the night sleep. In addition, heart rate and motor activity were continuously recorded using a two-channel ambulatory monitoring system (Minilogger, MedNATIC). Heart rate recordings were taken (in bpm) by a modified Lead derivation from Nehb (cf. Halhuber et al., 986). Motor activity was recorded by means of an activity sensor attached to the left thigh. The 24 hour data were stored in the memory unit of the equipment system and then transferred to a computer which then constructed an individual data file. Artifacts (defined for systolic blood pressure

12 Objective characteristics of jobs affect blood pressure 2 (SBP) and diastolic blood pressure (DBP) as any of the following: SBP < 50 mmhg, SBP > 250 mmhg, DBP > SBP, DBP < 30 mmhg, DBP > 50 mmhg, HR < 40 bpm) were excluded. Posture (supine, sitting, standing) and levels of physical activity have a strong influence on ambulatory blood pressure and heart rate (Pickering, 99). To ensure the comparability between work and home data, all analyses are based on data recorded only in the sitting, standing or lying position, and excluding physical activity (in analysing data of the activity sensor). Statistical Analyses For data analysis, the 24-h-measurements were divided into 5 periods: S S S S work was defined as all the time spent doing paid work; journey to and from work; leisure time was defined as consisting of a number of occupations in which an individual may indulge of his own free will. Leisure time can be spent in recreation, relaxation, self-improvement, or social participation (Dumazedier, 960); obligatory time was defined as time spent for household duties, child care, social work (e.g. taking care for the elderly or ill, political work, work in a club, etc.) or vocational advanced training, but also for hygiene, eating (Hoff, 986; Opaschowski, 997); S night was defined as time spent in bed without any activities (lights out). Time at work was defined from women s handheld computers and the setting protocols based on post-exploration (just after the 24 h ambulatory monitoring). Night-time was defined as all sleeping hours judged from participants handheld computers, the postexploration and the motor activity data. All readings for systolic and diastolic blood pressure, and for heart rate within each period of time (work, obligatory time, leisure time, night) were averaged to represent that period. Furthermore, a value representing the nocturnal change in the blood pressure in relation to the mean level during the daytime was calculated. The reason is that sleep has the effect of decreasing ( dipping ) blood pressure by an average of 0 to 5 percent of the daytime level in most individuals. However, some people s blood pressure does not dip over night or the blood pressure decrease is relatively small. Non-dipping is believed to be pathologic because it exposes the patient to a higher blood pressure load throughout the 24-h day (Käppler, 994; Dimsdale & Heeren, 998). Studies using dipping as a parameter differ according to the definition for the time frame of dipping, and for the physical activity during the daytime. Most investigators contrast the daytime blood pressure with the night-time blood pressure, using limited intervals, e.g. between 6 am to 0 pm for daytime and 0 pm to 6 am for night-time (e.g. Ferrara et al., 998; Uzu et al., 999; Weir et al., 998; ). However, Nystrom et al. (996) found that such standardized day and night-time limits may lead to misclassification. Another important effect on blood pressure is the physical activity. Examining the effect of daily activity on nocturnal blood pressure fall, del Arco-Galan & Suarez (994) and Leary et al. (2000) reported that the classification of non-dippers is dependent on their physical activity

13 Objective characteristics of jobs affect blood pressure 3 during the day. However, most published studies do not report how this activity problem was dealt with. Due to the problems with time limits and activity, the present study used a more precisely defined time frame and took into account the physical activity by excluding the blood pressure of segments with activity (i.e. segments with movement like walking, physical work, and all motor activity recorded by the activity sensor that was > 5 % were excluded) before averaging the daytime blood pressure. Daytime starts with the beginning of the ambulatory measurement. Night-time starts with the time of going to bed, no activities (e.g. sex, reading), and lights out, and finishes next morning with time given by subject s alarm clock or by getting up. Due to this restriction on data without activity, the 0 percentage difference was used as a boundary for the classification of dipper and non-dipper (instead of the 5 % difference, which is also frequently used). At first the nocturnal reduction rates (NRR) of SBP and DBP were calculated according to the following formula: NRR (%) = [(daytime mean - nighttime mean) / daytime mean] x 00 Then the women were divided into two groups according to the presence (dipper) or absence (non-dipper) of a reduction in both systolic and diastolic blood pressure during the night by an average of more than 0% of the daytime blood pressure. Between-group differences were performed to assess the relations between job strain (yes versus no) and blood pressure, sleep characteristics as well as the introspective variables (e.g. affect, perceived control etc.). Between-group differences for continuous variables were assessed by using ANOVA and two-sample t-tests, and those for discrete variables were assessed by using chi-squared tests. All ANOVAs with blood pressure included the women s age and the bodymass index as covariates. Results Objective task analyses depend on strain The results of the multivariate variance analyses of the five work-related dimensions with the exposure to high or low job strain yielded highly significant differences in all dimensions with the only exception being the dimension responsibility (see Table 3). Table 3 Results of Multivariate ANOVA for the five Work-related Dimensions (A-E) and the General Job Quality (F), as well as of the Between Group Differences for each Scale Work-Related Dimensions (A - E) and Pertinent Scales Max Mp Strain ANOVA Low M High M df df2 F p A) technolog./organizational work characteristics Pillai-test: ***

14 Objective characteristics of jobs affect blood pressure 4 work cycle time sequential completeness number sub-tasks organization tasks possibility of prediction information about organization information about results procedural degrees of freedom temporal degrees of freedom work-related decision processes feedback quantity/quality-conflicts physical demands *** *** *** *** *** *** *** *** ** B) work-related cooperation and communication Pillai-test: *** amount of cooperation kind of cooperation kind of communication *** * *** C) responsibility Pillai-test: responsibility for results, processes or people individual vs. group responsibility for results D) mental regulation requirements mental demands *** E) learning potential Pillai-test: *** qualification application requirement to learn new things *** F) general job quality (all scales of TDS) Pillai-test: *** Note. n = 4 for the exposure to low job strain; n = 7 for the exposure to high job strain; *p<.05; **p<.0; *** p<.000; Max = maximum of scale (the minimum of each scale is zero); Mp = threshold value of TDS which define the minimal profile; the minimal profile should be met in order to avoid fatigue, stress, monotony, psychosomatic complaints, or to lose skills; underlined are values which are below the Mp This means that the task design of women who were exposed to low job strain was significantly better than that of those exposed to high job strain. In detail, the scores of all scales of the dimensions work-related cooperation and communication, mental regulation requirements and four of the eleven scales describing the technological-/ organizational work characteristics dimension were higher for women who were exposed to low job strain than those exposed to high job strain. Women did not differ in the possibility of applying their qualifications depending on the job strain exposure, but in their possibility of learning new things by carrying out the job (see line E in Table 3). Women of the high job strain group as compared with those of the low job strain group had significantly fewer possibilities to learn new things. Comparing the scores of the low strain group with the minimum task requirements, six of all 2 scores did not obtain the threshold of the minimal profile. These six scales were all scales of only one dimension, the technical and organizational work characteristics. In contrast, 3 of all scores of the high strain group in four of the five dimensions did not obtain the minimal profile. This means that the task design of women who were exposed to high job strain lead to a higher risk of negative strain outcomes than that of those

15 Objective characteristics of jobs affect blood pressure 5 exposed to low job strain. The question about overtime showed that 3 (of 4) women of the high job strain group and 9 (of 4) women of the low job strain group worked long hours. In detail, the three women of the high job strain group did an averaged overtime of 32.3 minutes a week (min = 0 hours, max = 5 hours a week). The nine women of the low job strain group did an averaged overtime of 52.7 minutes overtime a week (min = 0 hours, max = 0 hours a week). It is important to note that all women of the low strain group had adequate procedural degrees of freedom (basis for their classification as exposed to low job strain was that the procedural degrees of freedom were above the TDS minimal profile), whereas the procedural degrees of freedom for women who were exposed to high job strain were too low. All in all, neither did the two strain groups differ in the question whether they did overtime work [χ 2 (2, N = 58) =.36, ns) nor in the question about the amount of overtime (t (58)= ; ns). Physiological changes depend on the exposure to job strain The results of examining the question of differences in cardiovascular activation depending on the exposure to job strain are based on a reduced sample because women who were on anti-hypertensive medication had to be excluded from the statistical analyses. Furthermore, the number of women differs slightly in the five tested time intervals because of missing values. Such missing values resulted from the fact that not all women passed all time intervals during the day (e.g. some women had no leisure time) or women s body activation was too high during one or more daily interval and thus the data of such intervals had to be excluded from physiological data analyses. Daily blood pressure was influenced by the exposure to job strain. Results of ANOVA shown in Table 4 yielded significant differences in systolic and diastolic blood pressure during work and obligatory time with higher blood pressure values for the women who were exposed to high job strain compared with those exposed to low job strain. Additionally, systolic and diastolic blood pressure during the night differed significantly between the women of the high job strain group and the low job strain group with higher values for the high job strain group. There was no significant difference in the time (latency) required to attain the lowest systolic and diastolic blood pressure between women exposed to high job strain and those exposed to low job strain [SBP-latency, high job strain: 3 hours and 5 minutes; low job strain: 2 hours and 54 minutes; F (, 34) = 0.0, ns; DBP-latency, high job strain: 2 hours and 29 minutes; low job strain: 3 hours 2 min; F (. 34)=0.92, ns]. However, the lowest diastolic blood pressure obtained, but not the lowest systolic blood pressure, was significantly higher in women exposed to high job strain than in those exposed to low job strain (see Table 4). The analysis of the lowest systolic blood pressure yielded only a marginally significant difference depending on the exposure to strain. Table 4 Analyses of Variance for Blood pressure by Exposure to Job Strain Daily Segment Job Strain SBP DBP

16 Objective characteristics of jobs affect blood pressure 6 M SD M SD Work High Low F (, 45) = ** * Obligatory Time High Low F (, 45) = * * Leisure Time High Low F (, 42) = ns ns Recovery Period High Low F (, 40) = * (*) Night High Low F (, 43) = * * Lowest Value High Low F (, 43) = (*) (*) NRR High Low F (, 44) = ns ns Note. NRR = nocturnal reduction rate Neither a significant difference in the nocturnal reduction rate for the systolic blood pressure nor for the diastolic blood pressure were observed depending on strain. Heart rate recorded during work, leisure time, obligatory time, night and during recovery, as well as the lowest heart rate, the latency to attain this lowest heart rate and the nocturnal reduction rate did not differ between women who were exposed to high and those exposed to low job strain (F s ranged between 0.02 and 3.0, p s between.086 and.374). Altogether, 4 of 45 normotensive women were classified as non-dipper (for 3 women dipping-status could not be determined). A significantly higher percentage of women exposed to high strain were non-dippers, n = 6 (54,5%) [dippers, n = 5 (45.5%)] as compared with women exposed to low strain, non-dippers, n = 8 (23.5%), dippers, n = 26 (76.5%), χ 2 ( N = 45) = 3.73, p <.05. Changes of mood depend on strain Daily mood was not influenced by strain. For the Positive and the Negative Affectivity, no significant differences were observed between women of the high job strain group and the low job strain group (see Table 5). However, women who were exposed to high job strain perceived significantly more stress and less control during their obligatory time than

17 Objective characteristics of jobs affect blood pressure 7 women exposed to low job strain. In addition, the women of the high job strain group perceived significantly less control during their leisure time than those of the low job strain group. Table 5 Results of Multivariate ANOVA for Rating Mood, Stress and Control during the three Daily Segments Work, Obligatory and Leisure Time, and one Measurement Point Before Going to Bed, as well as of the Between Group Differences for each Scale Daily Segment Variable Exposure to Job Strain ANOVA Low M High M df df2 F p Work Pillai-test: ns Positive Affectivity Negative Affectivity perceived stress perceived control ns ns ns ns Obligatory Time Pillai-test: (*) Positive Affectivity Negative Affectivity perceived stress perceived control ns ns * (*) Leisure Time Pillai-test: ns Positive Affectivity Negative Affectivity perceived stress perceived control ns ns ns * Before going to bed Pillai-test: ns Note. Positive Affectivity Negative Affectivity perceived stress perceived control Rating the items for the Positive Affectivity and Negative Affectivity was based on bipolar seven point scales ranged between -3 to +3.The lower the score the more negative the experience. Rating the items for perceived stress and control was based on unipolar seven point scales ranged between not at all () to completely (7). (*) p <.0; * p <.05 ns ns ns ns Evaluation of sleep and relaxation ability The distribution of subjects with sleep disturbances such as insomnia did not differ depending on strain, χ 2 ( N = 54) = 0.28, ns. However, significantly more women with disturbed relaxation ability were found in the high strain group than in the low strain group. Furthermore, significantly more women exposed to high job strain had problems falling asleep than those exposed to low strain group (see Table 6). However, the sleeping duration rated by the Sleep Wake Experience List (van Diest, 990) with a limit of seven hours (less than seven hours sleep duration is a short sleep duration; sleep duration is regarded normal if subjects slept 7-8 hours) did not differ depending on the exposure to job strain. The shortest rated sleep duration which was found in the high job strain group was six hours and in the low strain group five hours.

18 Objective characteristics of jobs affect blood pressure 8 Table 6 Relaxation Ability and Problems Falling Asleep as related to Job Strain Exposure Variable Exposure to Job Strain Low High Disturbed Relaxation Ability Yes No χ 2 ( N = ) 6.93** Problems to Fall Asleep Yes No χ 2 ( N = ) 6.60** Reduced Sleeping Duration Yes ( < 7 hours) No ( > 7 hours) χ 2 ( N = ) 0. Note. ** p <.00. One of the 58 women did not completely fulfilled the questionnaires. The sleep duration was not only rated by questionnaire for the last three months, but also tested for the night of ambulatory monitoring. There were no differences found in the sleeping duration during the monitored night between the two job strain groups, t (58) = -.4, ns. Women exposed to high job strain spent seven hours and minutes in bed (lights out, no motor activity), and women exposed to low job strain spent seven hours and 20 minutes in bed. It has to be examined whether the burden following the working time caused the disturbed recovery. Therefore, the amount of leisure time, obligatory time and time for household duties were examined between the two job strain groups. The results of variance analyses (Table 7) showed no differences in the amount of the leisure time, obligatory time and time within the obligatory time for household duties. Table 7: Duration of Daily Segments as Related to the Job Strain Exposure Daily Segment Job Strain duration (in min) M SD Obligatory Time

19 Objective characteristics of jobs affect blood pressure 9 Low High t () Time for Household Duties Leisure Time Low High t () Low High t () ns ns ns Discussion Objectively assessed job strain By using an objective method of analysing psychosocial work characteristics and conditions of work places, a configuration of subscales for classifying work places was defined according to the exposure to high versus low job strain. Based on this classification, it was examined whether the other work characteristics tested by objective work analysis (Task Diagnosis Survey, Rudolph et al., 985; Hacker et al., 995) differ between the two job strain groups. Work places with a potential to expose employees to high job strain showed deficits in four of the five work related dimensions tested by TDS (a total of 66.7 % of all tested subscales were below the minimal profile). Special emphasis should be given to the low rated subscales of sequential completeness, organization tasks, possibility of prediction, work-related decision processes, feedback and quantity/quality-conflicts as well as all subscales of the dimension work-related cooperation and communication. Each of the work characteristics defined by these subscales needs to be re-designed since the values did not meet the threshold values of the minimal profile. This minimal profile of the Task Diagnosis Survey (Rudolph et al., 985; Hacker et al., 995) defines the values that should be attained in order to exclude the probability of negative short-term effects such as fatigue, monotony, stress or psychical saturation. Work places of both the women exposed to low job strain as well as the women exposed to high job strain were characterized by too low physical demands (TDSsubscale physical demands asked for posture and movement-activity). Low physical demands, combined with time pressure and lack of influence over one s work (high job strain), are seen as high risk for muscular problems, e.g. lower back, shoulder and neck pain (Lundberg, Dohns et al. 999; Sandsjö et al., 2000; Wærsted, 2000). Therefore, the low physical demands have to be evaluated as an additional stress factor for women who were exposed to high job strain. However, independently of the exposure to low or high job strain, chronic under-activity has generally been considered to contribute to health problems (see the allostasis model of McEwan, 998; Sjøgaard, Lundberg, Kadefors, 2000).