It is important to analyze and limit the effects of job demands on employees' health. This is reflected by the objective of the German Safety and Health at Work Act (ArbSchG, 1996), that is, to secure and protect employees' health in the workplace through occupational health interventions. In October 2013, an amendment of this law added the assessment of psychological stress at work as a duty of the employers in § 5 (ArbSchG, 1996) stressing the importance of psychological risk factors for the health of the employees. Also, the assessment should be based on empirical results (§ 4 ArbSchG, 1996). The provision of these empirical results is an import task of research in occupational psychology. Thus, this study wants to contribute to a better understanding of the relationship between risk factors (job demands) and health behavior (presenteeism) in the field of scientific research. This field is of crucial importance in the rise of information societies. In 2014, 236,000 persons were officially employed as scientific staff in Germany (Konsortium Bundesbericht Wissenschaftlicher Nachwuchs, 2017), underlining that this field is of considerable relevance.

On the one hand, a sample from this field was chosen because the combination of job demands like unique tasks (e.g., writing a doctoral thesis), which cannot be done by colleagues in a case of absence (lack of replaceability), accumulation of work and time pressure may be very specific. On the other hand, the interactions of different types of job demands are not well understood (van Woerkom et al., 2016), especially in terms of relationships to health behavior like presenteeism (working while being ill). Therefore, the results from other occupations may not be applicable to scientific staff. In the following, we provide an overview of job characteristics that are typical for the scientific field.

The working conditions of scientific staff in different countries are already well described, including the scientific staff in Germany (Cyranoski et al., 2011). For reasons of comparability of the job characteristics, we will focus on young scientific professionals and exclude professors from the analyses. The majority of these young scientific professionals may aim for a PhD (PhD students) or may already have finished their doctor thesis but has no professorial job (postdocs). We will analyze PhD students and postdocs in a single group because their job characteristics may be similar (Konsortium Bundesbericht Wissenschaftlicher Nachwuchs, 2017). For instance, German PhD students and postdocs are often confronted with role conflicts and inconsistent expectations regarding participation in research, teaching, and administration as well as increasing workload and working hours (Kaba-Schönstein and Bonse-Rohmann, 2011; Konsortium Bundesbericht Wissenschaftlicher Nachwuchs, 2013). In Germany, PhD students and postdocs are frequently present and easily accessible in their workplace. They have a special function for the communication of their working group, that is, the participation in administrative tasks, while their integration in the distribution of tasks, responsibilities, and decisions is often unclear (Stock et al., 2002).

Furthermore, Germany also lacks permanently employed, independent instructors and scientists who are employed at a level below full professorships. Codes of conduct in teaching and science bind the majority of PhD students and postdocs while their decision latitude depends on their supervising professors (Borgwardt, 2013). In addition, structural developments and conditions increase the complexity and dynamics within German scientific institutions (Klinder and Fuhrmann, 2011).

In practice, the increasing demands on scientific staff (employed below the level of full professorship) present themselves as increasing evaluations and competitions like teacher evaluations, a rising pressure to publish, and a heightened proportion of research financed by third party funding (Kaba-Schönstein and Bonse-Rohmann, 2011). This as well as the constant need to reapply for jobs because of non-permanent contracts results in very high quantitative and qualitative job demands and consequently in time pressure (Semmer et al., 1999) and accumulation of work, which describes the degree to which work is left undone, for example, in the case of employees' absence through sickness.

However, the exclusive description of the status quo is not sufficient. High job demands like temporary employment have the potential to negatively influence employees' health (e.g., Waenerlund et al., 2011). At the same time, health-related behavior is a mediator between working conditions and health (e.g., Deery et al., 2014). Thus, it is necessary to analyze the relationship between working conditions and health-related behavior; in this case the health-related behavior of academic employees, to further investigate and quantify this negative effects on health in a specific field.

Presenteeism (a health-related behavior) is a serious issue in the workplace. A representative study in Germany showed that fifty percent of the employees worked at least two times within the past 12 months while being ill. Thirty-six percent did this even against medical advice at least once within the past 12 months (DGB-Index Gute Arbeit GmbH, 2009). Moreover, presenteeism has negative correlations with monetary and health outcomes like productivity and decreased future health (and therefore future absence from work; Taloyan et al., 2012; Janssens et al., 2013; Miraglia and Johns, 2015). At the same time, the pressure to be present at the workplace induced by supervisors is positively related to presenteeism in employees even if absence would be legitimate, for example, because of serious illness. This pressure is primarily high in organizations with low replaceability (e.g., in scientific organizations; Marr, 1996; Ashby and Mahdon, 2010; Henneberger and Gämperli, 2014). Also, time pressure and accumulation of work are probable in the context of low replaceability and are positively correlated with presenteeism (Aronsson and Gustafsson, 2005; Demerouti et al., 2009). These direct links seem to point out to mediating mechanisms explaining the relationship between job demands triggering attendance pressure (e.g., supervisorial pressure) and presenteeism (Miraglia and Johns, 2015). However, the understanding of these mediating mechanisms (Miraglia and Johns, 2015) and of the interactions between different job demands (van Woerkom et al., 2016) as well as their relationship with presenteeism is limited, especially in the scientific field.

Therefore, the first aim of this study is to examine the relationships between specific job demands (supervisorial pressure, time pressure, and accumulation of work) and the health behavior of academic staff in case of illness, specifically in the form of presenteeism. A second aim is to contribute to the literature by clarifying how these different job demands interact and how these interactions may be related to presenteeism in the scientific field. The results may contribute to both, future presenteeism research as well as the development of guidelines for practitioners.

We will first introduce a behavior based concept of presenteeism. Subsequently, antecedents of presenteeism within the context of the job demands-resources framework (JD-R; Bakker et al., 2014) and the conservation of resources theory (COR; Hobfoll, 2001) will be presented. Finally, we will develop our conceptual model (Figure 1) as well as our hypotheses. Our conceptual model states a positive direct and indirect relationship (via time pressure) between supervisorial pressure and presenteeism as well as a moderation of the relationship between supervisorial pressure and time pressure through accumulation of work.

Many different definitions of presenteeism are used in the literature. For example, presenteeism is defined as excellent attendance, working with productivity loss, or as the opposite of absenteeism, which is the absence from work (for an overview see Johns, 2010). However, a behavior based definition of presenteeism (Hägerbäumer, 2011) may be preferable (Johns, 2010), for instance, “Presenteeism is the behavior of employees to work while having symptoms of a disease” (Hägerbäumer, 2011, p. 76).

This behavior based definition by Hägerbäumer (2011) provides some advantages. The first advantage is that it is a completely behavior based concept that does neither include any antecedents (e.g., job insecurity) nor consequences (e.g., productivity loss) of presenteeism. Thus, antecedents and consequences can be analyzed empirically and independently from presenteeism, which is important for the scientific utility (Johns, 2010).

The second advantage is that the definition by Hägerbäumer (2011) does not include an evaluation of the behavior like “Sickness presence, that is, going to work despite judging one's current state of health as such that sick leave should be taken” (Aronsson and Gustafsson, 2005, p. 958). This is important because presenteeism can have positive or negative consequences. On the one hand, there may be positive consequences of presenteeism, for instance, on psychological diseases, chronic pain, and musculoskeletal disorders (Bödeker and Hüsing, 2008; Howard et al., 2009). On the other hand, research found an increasing effect of presenteeism on future suboptimal health and sickness absences (Gustafsson and Marklund, 2011; Taloyan et al., 2012).

A case of illness can be seen as a loss of resources and therefore as a stressful situation (Hobfoll, 1989) requiring action (coping strategy) to avoid further loss (e.g., due to missing deadlines). A possible coping strategy may be presenteeism as an attempt to maintain performance and limit detrimental effects due to illness at work. Health status and performance also vary because of present demands (stressors) and available resources. If the employee is not fully recovered from recent demands, job demands can turn into job stressors (Meijman and Mulder, 1998). Within the JD-R (Bakker et al., 2014), job demands can trigger a health impairing process (Bakker and Demerouti, 2007). In stressful situations, for instance getting the flu while facing important deadlines at work, people try to keep up their performance (Hockey, 1993) and to avoid further loss of resources, an attempt which requires physical and/or psychological effort (Hobfoll, 1989; Bakker and Demerouti, 2007). According to the COR theory (Hobfoll, 1989) people draw on other resources like their health, wellbeing, or social capital in stressful situations, in order to avoid a net loss of resources (coping). Because coping is always associated with the use of appreciated resources, coping can initiate a vicious circle of loss and negative net investments for persons with already small repertoires of resources. They therefore try to avoid the loss until all resources are used up (Hobfoll, 1989). Thus, a careful consideration between costs (invested resources) and anticipated benefits (maintaining potentially or actually threatened resources) has to take place (Hägerbäumer, 2011). In fact, job demands may be related to organizational outcomes like presenteeism through strain (Bakker and Demerouti, 2007; Demerouti et al., 2009; Thun and Løvseth, 2016) and impaired health (Miraglia and Johns, 2015).

Descriptives, reliabilities, and correlations between the variables are presented in Table 1. Four control variables were significantly related to presenteeism (i.e., sex, difficulties to pay bills, health status, irritation) and were thus included in the regression analyses (see Table 1).

Irritation was the only control variable significantly related to time pressure (B = 0.15, SE = 0.06, p < 0.05; Table 2) and presenteeism (B = 0.23, SE = 0.07, p < 0.01). Sex, difficulties to pay bills, and health status were not significantly related to time pressure nor presenteeism. Supervisorial pressure (B = 0.49, SE = 0.06, p < 0.01) was significantly positively related to time pressure. Both, supervisorial pressure (B = 0.32, SE = 0.07, p < 0.01, direct effect) and time pressure (B = 0.28, SE = 0.07, p < 0.01) were significantly positively related to presenteeism.

In line with Hypothesis 1, time pressure partially mediated the positive relationship between supervisorial pressure and presenteeism (B = 0.14, SE = 0.04, p < 0.05; indirect effect). The model explained 38.5% of the variance. Therefore, Hypothesis 1 was supported.

Hypothesis 2 postulated that accumulation of work moderates the positive relationship between supervisorial pressure and time pressure such that the relationship is stronger if accumulation of work is high compared to if accumulation of work is low (first stage moderated mediation). Accumulation of work (B = 0.16, SE = 0.06, p < 0.05) was significantly positively related to time pressure. Contradicting Hypothesis 2, the interaction between supervisorial pressure and accumulation of work was significantly, but negatively related to time pressure (B = −0.16, SE = 0.07, p < 0.05). The effect of supervisorial pressure on time pressure is weaker if accumulation of work is high (Figure 2).

As additional information, the conditional indirect effect of supervisorial pressure on presenteeism (through time pressure) with its continuous lower (−1 SE) and upper bounds (+1 SE) are displayed for three different levels of accumulation of work, that is, for the mean, for one SD below the mean and for the maximum obtained value (as one SD above the mean was outside the range of data; Figure 3).

The conditional indirect effect was positive, significant, and strongest when accumulation of work was low (B = 0.18, SE = 0.06, p < 0.05). For accumulation of work equal to its mean (B = 0.14, SE = 0.04, p < 0.05) and high levels of accumulation (B = 0.11, SE = 0.03, p < 0.05) the conditional indirect effect weakened. The index of moderated mediation was significantly negative (B = 0.05, SE = 0.02, p < 0.05; Table 2). In summary, the data do not support Hypothesis 2, that is, accumulation of work moderates the positive relationship between supervisorial pressure and time pressure such that the relationship is weaker (not stronger) if accumulation of work is high compared to if accumulation of work is low (first stage moderated mediation).

The results of the hypotheses' tests by regression analyses are essentially the same when tested without control variables (respective tables upon request from the authors).

With this study, we contribute to the understanding of psychological risk factors at work in order to help secure and protect employees' health. Job demands can be risk factors because they can lead to negative outcomes, such as increasing health problems (Schaufeli and Taris, 2014). Thus, the first aim of this study was to examine the relationships between specific job demands and the behavior of academic staff in case of illness, that is, presenteeism. The results of this study support that both, supervisorial pressure and time pressure have a positive relationship with presenteeism in the scientific field. This is in line with the findings by Ashby and Mahdon (2010) and Demerouti et al. (2009). Moreover, the data provide evidence for an indirect relationship between supervisorial pressure and presenteeism via time pressure (Hypothesis 1). High levels of supervisorial pressure are related to higher time pressure, which in turn is related to higher levels of presenteeism. These findings are in line with previous findings, which found that supervisors have an influence on employees' (perceived) work characteristics (Picocolo and Colquitt, 2006; Nielsen et al., 2008; Rooney et al., 2009; Holstad, 2014; Rigotti et al., 2014) and that workload is related to health indicators like fatigue and headache (Nixon et al., 2011) as well as health behavior like absenteeism (Bakker et al., 2003) and presenteeism (Demerouti et al., 2009). Thus, this study may support the application of findings about negative supervision, time pressure, and presenteeism from occupations like facility management, banking, auditing, education, and social services to the scientific field.

The second aim of this study was to contribute to the clarification of how different job demands interact and how these interactions may be related to presenteeism in the scientific field. Although well established in the broader stress literature (Lavee et al., 1987), the effect of concurrent demands, which increase the probability for negative outcomes through one specific stressor, is not well researched in professional contexts. Our data provide support for a multiplicative rather than additive interaction of supervisorial pressure and accumulation of work for time pressure. This interplay between the three job demands is related to presenteeism, but in an unexpected way. We argued for a strengthened conditional indirect relationship between supervisorial pressure and presenteeism (via time pressure) if accumulation of work is high. An intensification is plausible within the context of COR (Hobfoll, 2001), because it states that resource loss resulting from dealing with a job demand weakens the resource pool and therefore the capacity to deal with another job demand. Also, van Woerkom et al. (2016) showed for employees of a Dutch mental health care organization that the relationship between one job demand and negative outcomes (absenteeism) strengthened with another increasing work demand. However, our results show that the conditional indirect effect of supervisorial pressure on presenteeism is actually weakened if accumulation of work is high. In other words, in case of high accumulation of work the supervisorial pressure had only a minor association with presenteeism compared to in a situation with low accumulation of work in our study. It seems possible that job demands do not accumulate but substitute each other in the scientific field. Thus, future research is necessary to clarify which findings of interacting job demands in other occupations can be applied to scientific staff. Comparative studies between different occupations may give interesting insights into the complex processes of presenteeism.

Our findings may reflect a substitution effect, that is, substitutes for leadership “will not only tend to affect which leader behaviors (if any) are influential, but will also tend to impact the criterion variable” (Kerr and Jermier, 1978, p. 395). Within the leadership substitutes theory (Kerr and Jermier, 1978), situational (e.g., intrinsically satisfying tasks), individual (e.g., indifference toward rewards), and organizational characteristics (e.g., organizational formalization) can undermine the effect of leadership behavior (Podsakoff et al., 1993; Yagil, 2002). Thus, if the task itself requires frequent attendance, a strict controlling supervisor may be unnecessary. Therefore, accumulation of work may substitute supervisorial pressure and reduce its relationship with time pressure among scientific staff. Also, individual characteristics of PhD students and postdocs, like intrinsic interest in the task, may have an impact. If the task itself is satisfying, supervisorial pressure may be unnecessary to foster the attendance. One indicator may be the low average of supervisorial pressure (M = 2.80, SD = 1.80, on a seven-point scale). Taking into account the motivational potential of the tasks is a very interesting avenue for future research.

Another interesting issue is the concept of presenteeism for scientific staff itself: supervisors may care less whether their staff attends work though being ill, as long as the work is done anyways. Supervisors may expect their staff to work from home in case of illness, thus presenting a challenge for the notion and measurement of presenteeism in the scientific field but also to the many other kinds of jobs where people may work from home. Accounting for this issue is central to the future research of antecedents and consequences of presenteeism.

Overall, our study contributes to a better understanding of the interplay of leadership, job demands and the behavior in case of illness among scientific staff by considering interactions between different types of job demands and leadership.

Although highly speculative, threshold models following social exchange theories, such as Adams's (1965) equity theory, may explain the results. Adams postulates that people strive for equity, that is, a balanced relationship between their efforts (e.g., working performance) and benefits (e.g., good working conditions) in social contexts. This evaluation includes the comparison of the experienced ratio of efforts and benefits either with a desired reference or with the ratio of significant others. Thereby, equity theory implies the existence of a threshold for reactions toward changes of the ratios. A threshold is passed if the own ratio is significantly different from the ratio of a significant other (e.g., a colleague).

This concept is also known in the literature about psychological contract breach. Rousseau and Tijoriwala (1998) define psychological contracts as “an individual's belief in mutual obligations between that person and another party, such as an employer (either a firm or another person). This belief is predicated on the perception that a promise has been made and a consideration offered in exchange for it, binding the parties to some set of reciprocal obligations” (p. 679). Thus, contract breaches are perceptions by persons that obligations in this exchange process have not been met (Rousseau, 1995). People evaluate if changes in these obligations are in their “zone of acceptance” (Rousseau, 1995, p. 148). If the change is important enough, that is, if the breach is outside the zone of acceptance, people may respond to it, for instance, with quitting their jobs. Although first signs of psychological contract breach do not seem to affect the attitudes of the employees, responses suddenly take place when a threshold is reached (Rigotti, 2009).

It is possible that academic staff evaluates its efforts and benefits ratio in a case of illness. Thus, specific levels of a job demand (e.g., supervisorial pressure) may relate to specific levels of perceived time pressure, that is, to perceived high levels of time pressure and therefore to show high levels of presenteeism while one job demand is increased (Hypothesis 1). Our data may show that high levels of supervisorial pressure are related to highest levels of time pressure, such that a threshold is reached. Thus, if another job demand is increased additionally (e.g., accumulation of work) the strain through these job demands seems to surpass this threshold and the perceived time pressure does not increase anymore (Figure 2). Therefore, the relational pattern between job demands and perceived time pressure might change, namely, the positive relationship between a single job demand and time pressure is weakened.

This study was carried out with informed consent from all subjects about our respect of their confidentiality and anonymity. All subjects participated voluntarily and were free to stop the survey at any time. Based on this assumptions, this kind of study do not need a ethical approval of a committee in Germany.

Both, TS and CD exchanged research ideas, discussed recent developments of topics like presenteeism and leadership and designed the outline of the article together during several meetings. CD collected data via an online survey within the context of a research project of the Department of Work and Organizational Psychology, Leipzig University, Leipzig (Germany). CD did the preparation and the analyses of the data. Both, TS and CD interpreted and discussed the results during several meetings and colloquia. CD drafted the article and TS revised/edited the article critically for important intellectual content. Both, TS and CD discussed the different versions of the draft during several meetings and telephone calls. TS did the language editing and proofing to improve the clarity of the manuscript and help highlight our research. TS and CD both made substantial contributions to the work reported in the article. Both, TS and CD give their final approval of the version to be published. Both agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.CD will act as a corresponding author for the paper.