Dynamics of stress generation and reduction in the nursing team at an oncology center

Objective: to represent the dynamics of stress generation, accumulation and reduction in the nursing team at an oncology therapy center. Method: a mathematical simulation model of system dynamics was developed based on data collection in loco. The model served to test the impact of three policies aimed at reducing stress in the team, namely i) increase in the service load; ii) increase in the size of shift teams and iii) reduction of service hours per bed. Results: the model showed that the policy of increasing the size of the team obtained the best results, with the absenteeism index stabilizing at 8%; staff at leave also stabilizing at 4-5 people per month, as well as accumulated stress reduced to baseline levels. Conclusion: measures to monitor physical and emotional demands, hiring staff, better technical training for so-called stressful activities, and a better distribution of tasks can be effective in reducing absenteeism rates and improving the quality of life of these workers.


Introduction
Health professionals have faced significant changes in work organization and work relationships, having to cope with stress to meet the demands of modern professional life (1) . Work-related stress (2) occurs when the worker reacts to demands and pressures that do not match their skills and knowledge and that challenge their ability to cope with stressful situations.
There are several effects of prolonged stress, such as depression and absenteeism, which in addition to representing physical and mental fatigue are signs of an aggravation to physical and emotional health (1)(2)(3) . In the hospital setting, the impact of occupational stress (4) in the performance of nursing professionals has been an important concern for managers because, in addition to affecting physical and mental health, it also affects their performance.
Due to the stress and the consequences that it can generate in the workplace, managers need to find ways to reduce it in teams and thereby improve the quality of care through reducing absenteeism (5) . However, little is known about which managerial policies are more efficient and about the time needed to effectively reduce absenteeism caused by stress.
Thus, researchers of this study chose to apply a methodology derived from systemic thinking, which focuses on the analysis of problems in which technical, human, and organizational components interact through computer simulation known as system dynamics (6) .
System dynamics can help in the explicit representation of the interrelationship between stressors and their effect on absenteeism. It can also point the way to better policies aimed at reducing the physical and emotional load of the nursing staff.
The purpose of this article is to represent the dynamics of stress generation, accumulation and reduction in the nursing team at an oncology therapy center. For this purpose, a mathematical model is used, following the methodology of the system dynamics.
The choice of this group of workers for the development of this model was due to the heavy physical, mental and emotional workload to which they are exposed, reflecting a sample strongly susceptible to illness at work. Sleep problems (5) , high levels of stress and exhaustion, and low job satisfaction are also common among nurses. Physical incapacity is not often the main reason for work leave, but it is presented as a preventive measure. Thus, the main contribution of this article is to provide a better understanding of the effectiveness of managerial policies aimed at reducing stress in nursing teams from the use of the model developed as a cost-effective test bench to evaluate the effectiveness of programs to improve quality of work or training sessions prior to implementation.

Method
The simulation model was developed following the methodological procedure of the system dynamics (6) .
System dynamics has been widely used to simulate problems in the areas of business and environmental management and energy planning, among others and more recently in several health problems (7)(8)(9)(10)(11) .
The system dynamics methodology uses differential equations to represent the behavior of the variables of interest in the model (6) , in which the main element is the so-called 'stocks'. Stocks are the variables that define the state of the system and change their value by the influence of rates. For example, the number of workers (stock) increases as more workers are hired (entry rate) and decreases as workers are cut off (exit rate). Mathematically, a system dynamics model can be represented by equations of the type (6) : Where: To participate, all informants should have experience in nursing, work, and personal experiences that could represent the status quo of the team. First, all participants answered the validated Burnout Inventory questionnaire for Brazilian culture (12) , which assesses workload and stress and the result revealed high rates.  Thus, the accumulated stress is the difference between the stress generated in period t, γ t e and the stress dissipated in the same period δ t e , represented in the language of system dynamics by the following equation: In other words, when the actual care capacity α t e is less than the scaled capacity β t e , the stress would accumulate above what it would have if the actual capacity met the demand completely.
The stress reduction δ t e responds proportionally to the accumulated stress ε t and inversely to the necessary shifts to dissipate stress, the constant τ, according to previous research (13) : The accumulated stress ε t contributes to the increase in the absenteeism rate -in addition to other factors κ 1redreducing the total available team ρ t d , and therefore compromising the formation of teams in shifts ρ t p , as shown by the following equations, where κ 1 , κ 2 , κ 3 are constants: The In summary, Figure 1 shows that when the reduction mechanism works properly, the system remains balanced.
However, when the reduction mechanism is not fully effective or when stress is generated at a higher rate, the accumulated stress tends to grow, leading to more work leaves and, therefore, increasing the rate of absenteeism and illness in the team.   hours per bed per shift). Figure 5 presents the results of this scenario for the same 5% and 10% increases in workload.
As can be seen in Figure 5, even with considerable increases in the demand (10%), the absenteeism rate

Discussion
This study presents the dynamics of stress generation, accumulation and reduction in the nursing team of an oncology sector and the absenteeism using a system dynamics model. The model used information and insights resulting from dialogues with some professionals in this sector.
It consisted of multiple feedback cycles containing a diverse range of components, including the number of team members, the effect of work leaves, the effect of stress on teams, the workload, the patient care and the rest hours.
The model offers data that allows the manager to control the demands of the work and to follow the evolution of stress among these professionals. In addition, it is possible to predict trends for future scenarios under various scenarios (14) , such as the situation of US military personnel with post-traumatic stress disorder and a possible aggravation of this situation due to the country's involvement in new conflicts.
One of the key values of systems models is that they show how a set of changes affects many aspects of a complex structure (13) . The creation of mathematical models represents the productive chain and favors to diagnose and to monitor problematic points in its structure using computational simulations, employing an easy-to-understand representation.
A unique perspective is offered to researchers and practitioners to view stress in the workplace as a dynamic process (7) .  on building good levels of employee performance if these effects are addressed, thus promoting the development of a better society as a whole (16) .
It is up to the organizations to adopt management policies aimed at improving the conditions of the health sector (17) , because at the moment they conclude that it was in the work that the suffering and the wear and tear were generated, the subject deserves attention of the management devices. Meetings with teams are important for planning activities that seek the valuation of different knowledge with emphasis on the experiences of professionals in order to maintain the workers' health.
Identifying and monitoring workplace problems using systems dynamics models can provide greater safety to the manager and thereby better monitoring of team work. In addition, a person working in a better work environment is more likely not to be stressed and not to be absent from work compared to a person working in a physically exhausting and psychologically depressing environment (18) .
Health and wellness management should begin with changing attitudes; the promotion of basic psychological satisfaction (i.e., autonomy, relationship and competence), well-being and health can avoid negative consequences for employees and organizations and can maximize organizational performance (19) . In addition, interpersonal relationships, dialogue (20) , and the meeting of the physical and emotional demands of the professionals are factors considered important to improve the quality of life at work.
Another important factor is the fact that patient satisfaction (5) is linked to staff absenteeism and, to increase patient satisfaction, managers need to find a way to reduce staff absenteeism in order to avoid burnout and improve the atmosphere in the workplace.
The model, with its dynamics, proposes changes to improve team support, psychosocial aspects, mutual collaboration in the execution of tasks, and work and family balance. Actions that seek to mediate relationship problems in teams are important (21) , because stress, disagreement and horizontal violence are common in workplaces.
In addition, oncological treatment involves work overload, lack of equipment, long and aggressive treatments, side effects, feelings of despair and panic of patients and death (22) , thus demanding more involvement, knowledge and emotional balance.
In a long-term perspective, it will be interesting to further explore the issues related to human interrelated factors to better understand the complexities of human

Conclusion
The presented system dynamics model is able Given the complexity of the nursing service and despite the limitations, it is expected that the present study will provide another alternative for nursing managers in coping with stress, absenteeism, and improving the quality of life at work.
Finally, additional research should be encouraged by applying the systems dynamics methodology to study stress and consequences in the work environment. www.eerp.usp.br/rlae