Iran Journal of Nursing

Introduction
As key members of a medical team, nurses play a vital role in providing care and increasing the efficiency of medical services and treatments in patients. Personality includes the components of temperament and character. Examining the temperament and character of people can lead to the identification of traits that can lead to success or failure in different situations or jobs. Temperament and character are also very important in nurses and need attention in the nursing profession. Various factors can affect the temperament and character. One of these factors may be the circadian rhythm, which is often disrupted in nurses. Considering the importance of evaluating the personality dimensions of temperament and character in nurses and the effects of the circadian rhythm and the lack of a study in this field in Iran, this study aims to determine the relationship between circadian rhythm and temperament/character of nurses working in selected teaching hospitals in Tehran, Iran.

Method 
This is a descriptive-correlational study with a cross-sectional design. The study population consists of all nurses working in teaching hospitals affiliated to Iran University of Medical Sciences. The study samples were 200 eligible nurses who were selected using a consecutive sampling method from different departments of 4 hospitals. To collect data, a demographic form, the morningness-eveningness questionnaire (MEQ), and Cloninger’s temperament and character inventory (TCI) were used. The MEQ has 19 items, and its total score ranges from 16 to 86, with higher scores indicating more morningness and lower scores indicating more eveningness. There are 5 classifications based on the MEQ score: Definitely morning type (score 70-86), moderately morning type (score 59-69), neither type (score 42-58), moderately evening type (score 31-41), and definitely evening type (score 16-30). Its internal consistency using Cronbach’s alpha coefficient is 0.86, with favorable test-retest reliability. The TCI has 240 items. In this study, the 125-item form was used as a self-report tool, which has seven components; four components related to temperament (novelty seeking, harm avoidance, reward dependence, and persistence) with 60 statements, and three components related to character (self-directedness, cooperativeness, and self-transcendence) with 65 statements, which are answered by true or false. Its internal reliability using Cronbach’s alpha is 0.66-0.87. To describe the data, descriptive statistics (frequency, mean, standard deviation, skewness, kurtosis) were used. Multivariate regression analysis and Pearson correlation test were used to test the research hypotheses in SPSS software, version 16.

Results 
Most of participants (40.5%) had age 30-39 years, and were male (66.5%) and married (64%), with a bachelor’s degree (51.5%) and moderate economic status (67%), and were contractual (60.5%) nurses (59%), with a work experience of 1-4 years (38.5%) and a morning or evening shift (40%). The findings showed that the mean MEQ score was 49.9±74.26, and most of them (64%) were neither-type nurses. Among the TCI subscales, persistence with a mean score of 68.6±23.85 and self-directedness with a mean and score of 43.6±16.84 had the highest and lowest scores, respectively. among other subscales. Among the items of the TCI, empathy with a mean score of 72.5±29.44 and compassion with a mean score of 33.87±19.55 had the highest and lowest scores, respectively. The correlation test results showed that circadian rhythm in overall had a negative significant correlation with persistence (P=0.039) and self-transcendence (P=0.047). Also, circadian rhythm had a significant relationship with age (P<0.001), sex (P=0.044), employment status (P=0.003), and work experience P<0.001). Novelty seeking, reward dependence, persistence, self-directedness, cooperativeness, and self-transcendence had a statistically significant relationship with the demographic characteristics of nurses. 

Conclusion 
Most of the nurses in the study hospitals were identified as a neither-type according to the MEQ score. Regarding their TCI score, the highest score was related to the persistence component and the lowest score was related to self-directedness. The circadian rhythm of nurses had a significant negative correlation with some components of TCI. Considering the impact of circadian rhythm on the quality of nursing care and considering the results of the present study which showed that evening-type nurses had weaker performance than morning-type nurses, the officials and hospital managers should gain sufficient knowledge of circadian rhythms, identify evening-type nurses, provide training, facilities, and special privileges to nurses, and determine their works shifts according to their circadian rhythms, so that they can improve the quality level of patient care and increase patient satisfaction.

Ethical considerations
Compliance with ethical guidelines
Ethical approval was obtained from the ethics committee of Iran University of Medical Sciences (code: IR.IUMS.REC.1400.559). Necessary explanations were given to the participants regarding the study objectives and methods, the right to leave the study at any time, and the confidentiality of their information.

Funding
This article was extracted from a master’s thesis registered by the School of Nursing, Iran University of Medical Sciences. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Authors’ contributions
Editing & review, initial draft preparation, data collection: Mojgan Fatemi; Project administration, completion of the final draft: Naiemeh Seyedfatemi and Shiva Khaleqparast; Investigation, methodology: Shima Haghani.

Conflict of interest
The authors declare no conflict of interest.

Acknowledgments
The authors would like to thank all the nurses participated in this study for their cooperation.


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