Effort-Reward Imbalance and Quality of Life Among Female Nurses at a General Hospital in Japan

An effort-reward imbalance (ERI) model is a measurement of psychosocial work stress. The ERI model with both the effort-reward ratios and the concept of overcommitment (OC) indicates that work stress is related to high effort with low reward. Effort is evaluated by measuring work demands. Reward includes money, esteem, status, and control over promotion prospects, and job security. Overcommitment is a set of attitudes, behaviors, and emotions that reflect excessive work effort13,14,18). This model has been used to study psychosocial work stress in various occupational groups. It has been suggested that the ERI model has a predictive power for poor physical or mental health2-3,6-8,10,12,14-16,18-21). Concerning overcommitment, according to Siegrist and Tsutumi et al., overcommitment causes emotional exhaustion and exacerbates the negative effects of the effort-reward imbalance14,18). Weyers et al. found that nurses who report higher ERI with high overcommitment scores were twice as likely to suffer from poor psychological health compared to those who report higher ERI with low overcommitment scores21). Aust et al. and Ire et al. found that overcommitment was significantly reduced in an intervention group through stress management programs or counseling1,4).

that poor physical and mental health were significantly related to higher effort-reward imbalance 10) .Weyers et al. examined the relationship between ERI, physical health, and mental health among nurses in Denmark and found that risks for poor health functioning were elevated among nurses who were experiencing high effort and low reward 21) .All previous studies suggested a significant relationship between ERI and health-related quality of life, and higher ERI is likely to be a risk factor for poor health.In Japan, Watanabe et al. investigated the relationship between ERI and health-related quality of life among Japanese employees of a manufacturing plant, and suggested that ERI was associated with health-related quality of life 20) .However, no research has been conducted among Japanese nurses to examine the relationship between ERI and health-related quality of life.
Nurses are exposed to high-stress work environments, including irregular work schedules, shift work, and interaction with patients and other hospital staff members.Tsutsumi found that the level of ERI in nurses and dental technicians in Japan was almost twice that of workers in production companies 18) .The research investigating the relationship between ERI and health-related quality of life among nurses is necessary to elevate their quality of life or to prevent physical or mental impairments or disease.
We had already investigated the relationship between the ERI and depressive state in the same sample 5) .In the previous study, depressive state was measured by one item of the quality of life (WHOQOL-26), i.e., item 26, which questioned how often the subject feels despair, anxiety or depressed mood.And we found that effort-money (effort-job promotion) imbalance and overcommitment had significantly influenced on depressive state.However, depressive state is an important problem for mental health but only a part of health functioning.In the present study, we investigated the relationship between the ERI and health functioning as a whole.
The aim of the present study was to investigate the effects of ERI on quality of life among nurses at a Japanese general hospital.

Subjects and procedure
A part of the present study was described elsewhere 5) .Subjects consisted of all the nurses (n=682) at a general hospital in Japan, which is located in urban and has 611 beds.We conducted the present study in November 2007.The questionnaire was distributed by supervisors and was returned by 465 nurses (response rate, 68.2%).Male nurses were excluded from the sample because there were so few (n = 13).Subjects with missing ERI values were also excluded (n = 46).The final sample consisted of 406 female nurses (59.5%).
Participants were asked to fill out a questionnaire explaining the voluntary of the survey, and we assumed that participants consented to the survey with answering the questionnaire.This self-report survey was approved by the Committee for the Prevention of Physical Disease and Mental Illness among Health Care Workers in the general hospital.

Work environment
The survey included demographic variables such as age and work-related variables (work style, occupational status, overtime hours, and shift work).Age was coded into a fourcategory classification and ranged from 20s to 50s or over (<30, 30 to <40, 40 to <50, and 50).Work style was either full-time or part-time.Occupational status responses included: manager, middle manager or subordinate.Overtime work responses were in hours per week.Shift work categories included: no shift work, shift work with night shift, or shift work without night shift.Table 1 shows the characteristics of the subjects.

Effort-reward imbalance
Work stress was measured using the Japanese version of the ERI (23 items) translated by Tsutsumi 19) .The ERI consists of three subscales: efforts (6items, e.g., quantitative and qualitative load), rewards(11items) and overcommitment(6items).The rewards subscale is further divided into three subgroups: esteem (5items, e.g., "I receive the respect I deserve from my superiors."),job security (2 items, e.g., "My job security is poor.")and job promotion (4 items, e.g., "My job promotion prospects are poor.").Overcommitment is measured by six items which refer to respondent's inability to withdraw from work obligations and to develop a more distant attitude towards job requirements.The validity of this questionnaire has been confirmed 18) .Higher ERI ratio and overcommitment scores indicate high-risk conditions.Means and standard deviations of ERI subscales and overcommitment are presented in Table 1.

Health-related quality of life
Quality of life was measured by the Japanese version of WHOQOL-BREF (WHOQOL-26) 17) .The WHOQOL-26 contains 26 items divided into the following domains: Physical Health (7 items), Psychological (6 items) Social Relationships (3 items), and Environment (8 items).The four domain scores denote an individual's perception of their quality of life in each particular domain.Higher scores represent better quality of life.The WHOQOL has been applied to assess health functioning 9,11) .

Statistical analysis
Four kinds of ERI ratios (effort-reward imbalance, effort-esteem imbalance, effort-job security imbalance and effort-job promotion imbalance) were calculated according to Tsutsumi 19) .The effort-reward imbalance was calculated as effort  11/reward  6.The effort-esteem imbalance was calculated as effort  5/esteem  6.The effort-job security imbalance was calculated as effort  2/security  6.The effort-job promotion imbalance was calculated as effort  4/job promotion  6.Higher scores of the three imbalances and overcommitment were defined as high-risk conditions.The lower tertile of the four domain scores of QOL were each assigned to the poor health functioning group (n =117, 111, 183, 120 for Physical Health, Psychological, Social Relationship, and Environment, respectively).The upper tertile of each of the four domain scores of QOL was assigned to the good health functioning group ( In the next step, the relationships between health functioning and work-related or ERI variables were examined using stepwise logistic regression.We used the tertile of the four domain scores as dependent variables and the ERI ratios, overcommitment scores, and the work-related scores as independent variables.The results are shown as odds ratios (ORs) with 95% confidence intervals (CIs).All analyses were conducted using SPSS 11 (SPSS Inc., Chicago, IL, USA).

Results
The four effort-reward ratios and overcommitment scores significantly correlated with poor health functioning in the four domains (Table 2~Table 5).

ERI and physical health domain
Shift work and overtime hours per week also significantly correlated with poor physical health functioning (Table 2).According to the stepwise logistic regression analyses between Physical Health and the work-related variables (shift work and overtime hours per week), the three imbalances (effort-esteem imbalance, effort-job security imbalance and effort-job promotion imbalance), and overcommitment, significant correlations were found with Poor Physical Health: a higher effort-job promotion ratio (OR, 0.24; 95% CI, 0.09-0.64)and higher overcommitment (OR, 0.64; 95% CI, 0.64-0.83)(Table 6).

ERI and psychological domain
We found significant differences for work style, shift work and overtime hours per week between the two groups (Table 3).According to the stepwise logistic regression analyses between Psychological and the work-related variables (shift work and overtime hours per week), the three imbalances, and overcommitment, significant correlations were found with Poor Psychological Health: a higher effort-job promotion ratio (OR, 0.25; 95% CI, 0.09-0.70)and higher overcommitment (OR, 0.71; 95% CI, 0.62-0.81)(Table 6).

ERI and social relationship domain
We found no significant differences for age or work-related variables (work style, occupational status, shift work, and overtime hours per week) (Table 4).According to the stepwise logistic regression analyses between Social Relationship and the three imbalances and overcommitment, significant correlations were found with Poor Social Relationship: a higher effort-esteem ratio (OR, 0.31; 95% CI, 0.13-0.71)and higher overcommitment (OR, 0.86; 95% CI, 0.79-0.94)(Table 6).

ERI and environment domain
We found significant differences for work style and shift work between the two groups (Table 5).According to the subsequent stepwise logistic regression analyses between Environment and the work-related variables (work style and shift work), the three imbalances and overcommitment, significant correlations were found with Poor Environment: a higher effort-job promotion ratio (OR, 0.27; 95% CI, 0.11-0.64),higher overcommitment (OR, 0.85; 95% CI, 0.77-0.94),and shift work (OR, 1.99; 95% CI, 1.04-3.80)(Table 6).

Discussion
The four effort-reward ratios and overcommitment scores of the poor health functioning group were significantly higher than those of the good health group in the four domains of the WHOQOL (Table 2~5).Moreover, all the effort-reward ratios of the poor health functioning group were above 1, and therefore were defined as a high-risk condition for poor physical and mental health 19) .
The significant association between Physical Health or Psychological domains of the WHOQOL and the ERI was similar to previous findings among hospital staff members, including nurses in other countries 10,15,21) .
The strength of our study is also that we investigated in detail the independent contribution of the three ratios of effort-reward imbalance (effort-esteem imbalance, effort-job security imbalance and effort-job promotion imbalance) and overcommitment to health functioning measured by the WHOQOL.Physical Health, Psychological, and Environment domains of the WHOQOL were each significantly associated with a higher effort-job promotion ratio and higher scores of overcommitment (Table 6).Social Relationship domain was significantly associated with a higher effort-esteem ratio and higher scores of overcommitment (Table 6).According to Chandola et al., the ERI has been extended to include general and close social relationships, and lack of close social relationships was For our results, the association between effort-esteem imbalance and Social Relationship partially agreed with the findings of Chandola et al., possibly indicating that nurses with higher effort-esteem imbalance tend to be dissatisfied with their social relationships.
For work-related variables and the WHOQOL, only shift work was significantly associated with the Environment domain.
The present findings suggest that nurses must reduce subjective feelings of overcommitment.In addition, improving the work situation-for example, better promotion prospects, higher salaries, respect from supervisors, or reducing the burden of shift workmay improve the physical and mental health of nurses.
In this study, overcommitment was associated with all four domains of the WHOQOL.In accordance with previous studies 1, 4,14,18) , overcommitment is a set of attitudes, behaviors and emotions that reflect excessive work effort, and is combined with a strong desire for approval.Therefore, the overcommitment that many nurses experience may be reduced through mental health services such as group cognitive psychotherapy.Such interventions may improve immediate and long-term health functioning.In the future, investigations should be done to determine whether such mental health services actually improve health functioning among nurses through a reduction of overcommitment.
From the position of occupational health practitioners, it is possible to improve working conditions such as shift work, or respect from superiors.Concerning shift work, planning shift duty in an orderly manner (ie.morning shift → afternoon shift → night shift → morning shift) will reduce the burden of work shift.We may be able to educate the supervisors and administrators about issues related to mental health of nurses; the stressors or burden for nurses, respect to their skill or the adequate support in difficult situations.
Nevertheless, the present study has some limitations.First, the sample size was small and only one general hospital was surveyed.A larger sample should be examined in the future.Second, our results were inconclusive about the impact of ERI on health-related quality of life.We should conduct follow-up studies to investigate the change of health functioning through reduction of nurses' overcommitment or improvement of the effort-job promotion imbalance and effort-esteem imbalance.
In spite of the limitations, our findings provide insight into the factors influencing health functioning among nurses in the general hospital.From a practical point of view, our suggestion to reduce feelings of overcommitment among nurses may be valuable for professionals who care for hospital nurses, such as occupational health practitioners.

Table 1 .
n =114, 116, 128, 121 for Physical Health, Psychological, Social Relationship, and Environment, respectively).The medium scores (n =175, 179, 95, 165 for Physical Health, Psychological, Social Relationship, and Environment, respectively) were all excluded from further analyses.Mean and standard deviation of the four domain scores of QOL are presented in Table 1.Characteristics of study subjects. www.intechopen.com

Table 2 .
Comparison between Poor and Good Physical Health groups.

Table 3 .
Comparison between Poor and Good Psychological groups.

Table 4 .
Comparison between Poor and Good Social Relationship groups. www.intechopen.com

Table 5 .
Comparison between Poor and Good Environment groups.

Table 6 .
Odds ratios of QOL domains by effort-reward imbalance and overcommitment.health 2) .Social Relationship domain of the WHOQOL included three items: satisfaction with human relations, support from friends, and satisfaction with sex life.