Psychosocial factors and mental work load: a reality perceived by nurses in intensive care units1

OBJECTIVE: To analyse the perception of psychosocial factors and mental workload of nurses who work in intensive care units. It is hypothesised that nurses in these units could perceive psychosocial risks, manifesting in a high mental work load. The psychosocial dimension related to the position's cognitive demands is hypothesised to mostly explain mental work load. METHOD: Quantitative study, with a descriptive, cross-sectional, and comparative design. A total of 91% of the intensive care unit populations of three Chilean hospitals was surveyed, corresponding to 111 nurses. The instruments utilised included (A) a biosociodemographic history questionnaire; (b) the SUSESO-ISTAS 21 questionnaire; and (c) the Mental Work Load Subjective Scale (ESCAM, in Spanish). RESULTS: In total, 64% and 57% of participants perceived high levels of exposure to the psychosocial risks Psychosocial demands and Double shift, respectively. In addition, a medium-high level of overall mental load was observed. Positive and significant correlations between some of the SUSESO-ISTAS 21 and ESCAM dimensions were obtained. Using a regression analysis, it was determined that three dimensions of the psychosocial risk questionnaire helped to explain 38% of the overall mental load. CONCLUSION: Intensive care unit nurses felt that inadequate psychosocial factors and mental work overload existed in several of the tested dimensions.


Introduction
Nurses who work in intensive care units (ICUs) take care of people with acute and/or chronic health problems that require permanent, specialised and highly specific nursing care. In addition, the nurses  (1)(2) .
Other work factors exist that can be damaging for these professionals, such as the organisational characteristics of the health care environment, the constant and high mental demands, routine performance issues, an insufficient number of human resources, and nocturnal and shift work. These factors can generate emotional alterations (e.g., irritability), the presence of somatic symptomatologies (e.g., migraines, gastrointestinal problems), dissatisfaction, burnout, stress (3) or mental fatigue (4). For these reasons, working conditions (5) -and organisational, work, technological and psychosocial factors in particularcarry great importance.
Psychosocial factors are understood to be the interaction between work, workers, the environment, satisfaction with the work performed and organisational conditions. In addition, these factors may also involve the capacity of the worker, his/her needs, culture and personal situations. These factors positively and negatively influence the health, welfare and performance of the worker (6)(7)(8) .
The consequences of psychosocial factors on health have been explored in various models, such as the Karasek and Theorell Job Demand-Control-Social Support model (9) and the Siegrist Effort-Reward Imbalance models (10) .
These psychosocial factors can be grouped as (a) psychological demands; (b) balance between tasks and work, family, and social time; (c) control over work; (d) social and instrumental support of colleagues and superiors, particularly quality of leadership; (f) work rewards; and (g) job security. These theoretical models have served as the basis for the development of the Copenhagen Psychosocial Questionnaire (CoPSoQ), an instrument adapted and validated in many countries, among them Chile, for the investigation, evaluation and prevention of psychosocial risks (11)(12) .
The objective of this research fundamentally involves the analysis of psychosocial risks that affect workers, their tasks and the organisation. In the area of Nursing, studies on stress and burnout have proliferated (13)(14) , leaving behind other psychosocial variables, such as mental workload (15)(16) , which is what has powered the development of this study.
Mental load is a multidimensional construct defined as the interaction between cognitive demands of a task (e.g., memory, attention), characteristics of the person (e.g., educational level, self-efficacy) and the characteristics of the situation (e.g., temporary pressure). Among its causes, the characteristics of the task must be mentioned (e.g., memory and attention demands), along with temporary pressures and work pace, functions to be performed, the degree of autonomy, and interactions with other people (17) .
The imbalance between demands of the task and workers' skills and characteristics can cause mental work overload or underload. Work overload is understood to be situations in which the worker is faced with more demands than he or she is capable of confronting.
Mental underload, however, is produced in positions with few tasks and little cognitive demand (qualitative underload) and/or simple tasks with sufficient time for execution (quantitative underload). Mental demands are one of the main sources of mental load, negatively affecting perception and resulting in damaging effects on both the heath of the workers and the achievement of the organisation's objectives (17)(18) .
The objective of this study is to analyse the   Of this total, 111 nurses responded to the questionnaire (91%). Data were not obtained from the remaining 9% (11 nurses) who were on leave or were absent from their respective institutions during the data harvesting period or who did not want to participate.

Materials and methods
For this investigation, three instruments were The ESCAM provides an average subjective mental work load in addition to specific scores for each dimension.
The scores range between 1 and 5, where 5 is high mental load and 1 is low, and includes cut-off points for the 25th, 50th and 75th percentiles. The scale has been validated for use in the Chilean population (20) .
The principal researcher applied the instruments in the order previously described using individual interviews The ethical principles of E. Emmanuel were considered throughout the study (21) .
For the data analysis, the Statistical Package of Social Sciences (SPSS)®, version 19.0, was utilised.
Statistical data cleaning was performed to verify that no multivariate outliers were present within the Mahalanobis distance (22) . Subsequently, descriptive statistics were calculated (averages, medians, standard deviations and percentages) for each of the variables.

Results
A total of 91% of the population of nurses working in ICUs of the three regional hospitals in Chile was surveyed, corresponding to 111 nurses (eleven nurses were absent or refused to participate, which corresponded to 9% of the sample    Table 1).
A total of 64% of the participants felt that their position involved a high volume of work in relation to the time available to perform it, requiring complex decision-making and constant attention, implying a high emotional wear. Likewise, 57.7% declared that, in addition to their position, they had to attend to familydomestic work demands. Additionally, 47.7% thought that their roles were not clearly defined and that the support of superiors and colleagues was insufficient.
In the Active work and skill development and Rewards dimensions, medium levels of psychosocial risk were perceived.
With respect to the mental work load, the overall mental work scores (M= 3.47) were above the scale median, with scores ranging from 2.5 to 4.9 (see Table   2). Likewise, in the mental load profile, scores above * Rotating shifts are an internal system of personnel distribution; in this study, it is called the "fourth shift", which corresponds to 12 working hours during the day (from 8:00 am to 8:00 pm), followed by a day of 12 working hours at night (from 8:00 pm to 8:00 am), followed by two days free. This rotation is utilised in the three participating units. It should be noted that in Chile, people work 44 hours weekly, independent of the shifts during which the work is performed.  Table 3). The correlation between the SUSESO-  Table 4). The condition

Discussion
The objective of this work was to analyse psychosocial and mental load factors that impact the work of ICU nurses. In general, participants perceive that their position is associated with psychosocial factors that carry high risks to health and mental work overload. ICU workers feel that they have greater autonomy and more significant tasks and professional development opportunities than those in intermediate care (2,23) . As for the type of contract, substitute workers compared to workers with fixed and indeterminate contracts receive fewer rewards in their positions. That is to say, they perceive less stability in their employment and less recognition on the part of their superiors and experience greater worry about the changes in the tasks assigned.
Additionally, those who work in rotating shifts perceive less social and instrumental support and have lower clarity of their roles than those who work day shifts. To set the level of load in each dimension, the scores were compared to the cut-offs established in a prior study that was conducted with a Spanish sample (18) . with the Job Demand-Control-Social Support model (9) and with Imbalance Effort Rewards model (10) , which highlight the influence of psychosocial factors on nurses' health (24)(25) .
In addition, it has been observed that the psychosocial factors Psychological demands, Rewards and Double shift explain more than one-third of the subjective mental load. In line with the third hypothesis formulated, the psychosocial factor related to the emotional and cognitive demands of the position is the one that most helps to independently explain overall mental load, which coincides with the empirical and theoretical aspects mentioned (1,17) .