Day surgery rates continue to increase. Outpatient procedures now account for more than 60% of all surgeries in some countries . In Sweden, a recent study found that day surgery accounted for 43% of all in-hospital procedures. Orthopaedic (33%), general (29%) and gynaecological (17%) procedures were the most common day surgeries, and the most common anaesthesia was a balanced general technique . Advances in surgical and anaesthetic techniques, particularly in day surgery, have rendered mortality and major morbidity rare events. Measurement of the quality of postoperative recovery from the patient's perspective is an important indicator of successful recovery after day surgery and anaesthesia .
Postoperative recovery consists of four dimensions, physiological, psychological, social and habitual recovery, and has been defined as an energy-requiring process of returning to normality and wholeness regarding activities of daily living and psychological well being . Patients admitted to day surgery are monitored postoperatively for only a short time prior to discharge, after which the responsibility for monitoring shifts from the hospital staff to the patient . Little is known about day surgery patients' postoperative recovery at home , and personality could influence their experience of recovery. Few studies have addressed the potential correlation between personality and how people recover after surgery [7,8]. Long-term follow-ups of patients undergoing coronary bypass surgery  and surgery for ulcerative colitis  have shown that personality traits involving poor optimism predict more postoperative depressive symptoms , and poor tolerance of frustration predicts more postoperative distress . To our knowledge, no studies have addressed the relationship between day surgery patients' personality traits and the quality of their postoperative recovery. Hence, this study aims to explore possible relationships between personality traits and the quality of postoperative recovery in patients undergoing day surgery.
Patients and methods
Our study included a consecutive sample of 260 patients undergoing day surgery at the department of day surgery in a university hospital in Sweden. The sample was drawn preoperatively from December 2004 to April 2005. We define day surgery as surgery performed on patients who are admitted, operated on, and discharged the same day. The inclusion criteria were those required for all day surgery patients at the hospital, that is, the patient should be aged over 18 years, be of reasonable health (ASA grades I or II, or in special cases, grade III), have a responsible adult and a telephone at home, and have adequate command of the Swedish language.
The short Big Five scale by Saucier  was used to assess personality traits. The short Big Five, the Mini-Markers subscale, was developed by Saucier  from the Big Five questionnaire by Goldberg . The Big Five consists of 40 adjectives, with responses on a 5-point scale rated from 1 (‘not at all’) to 5 (‘extremely’). Five traits are measured: ‘extroversion’ (sociable and outgoing), ‘agreeableness’ (altruism and empathy), ‘conscientiousness’ (impulse control, planning and organizing), ‘emotional stability or neuroticism’ (psychological maladjustment and more experiences of unpleasant emotions) and ‘openness to experience’ (imagination, curiosity and intellectualism) [9,11]. Compared with the original scale, Goldberg's 100-item scale is characterized by less use of difficult items and is easier to administer . The scores for each factor range from 8 to 40. Higher scores indicate greater extroversion, agreeableness, conscientiousness and emotional stability. Its psychometric properties are found to be acceptable, with a Cronbach's alpha of 0.83 . The instrument has been tested and found valid in a Swedish population, with a Cronbach's alpha of 0.84 .
Quality of recovery
To measure the quality of recovery, we used a modified version of the Quality of Recovery-40 (Mod QoR-40). Myles et al.[14,15] developed the first QoR-40 for different surgical procedures, but the modified instrument (Mod QoR-40) has been developed and tested specifically for day surgery patients . Psychometric properties supported three dimensions: ‘emotional state’ (eight items), ‘physical comfort’ (10 items) and ‘physical independence’ (five items). Three questions about general health, pain and current recovery complemented the three dimensions. The patient questionnaire includes 26 items to be answered.
Items in the three dimensions were scored on a 5-point scale (for positive items, 1, ‘none of the time’, to 5, ‘all of the time’; for negative items, the scoring was reversed). Higher scores indicate higher quality of recovery. The general questions about pain, health and recovery were scored on a 10-point scale (1, ‘very much pain’, to 10, ‘no pain’; 1, ‘very bad health’, to 10, ‘very good health’; 1, ‘no recovery’, to 10, ‘complete recovery’).
On admission to the day surgery unit, patients received both verbal and written information about the purpose and the procedure of the study and were informed that participation was voluntary. Demographics regarding sex, age, surgical procedure, ASA physical classification and the Big Five  were collected preoperatively. On discharge, patients received a Mod QoR-40 questionnaire  for postoperative day 1 and a prepaid return envelope. Questionnaires for days 7 and 14 were sent to the patients. No reminders were sent out.
The Regional Research Ethics Committee approved this study (Dnr 03-333). All participants were treated according to the ethical principles of human research. Each patient's verbal consent for the study was obtained before inclusion. They were provided with written information, and confidentiality of the data was assured. Patients had the right to withdraw from the study at any time.
We used Statistica version 7.0 (StatSoft, Tulsa, Oklahoma, USA) to analyse the data. Descriptive statistics are presented as arithmetic means and SD or frequencies when appropriate. Correlations were analysed using Spearman's rank correlation. All available data were used in the regression analysis, that is, if a patient answered the ‘emotional state’ but not the ‘physical state’ dimensions of the Mod QoR-40, he or she was included in the emotional state regression versus Big Five. For this reason, the correlation table presents both the number of included patients and the regression coefficient. Group differences (e.g. men or women, smokers or nonsmokers, etc.) were analysed using the Mann–Whitney U test. We estimated trends over the 14-day follow-up period by a three-point regression analysis (days 1, 7 and 14) of the scores calculated for each patient and expressed as the change in score per day. The trends were normally distributed and tested against zero using Student's paired t test. Statistical significance was set at a P value of less than 0.05.
Our study included 260 patients, but 12 of these patients became hospitalized and had to be excluded. Of the remaining 248 patients, 14 and 31 (total 45) patients did not answer the Big Five or the Mod QoR-40, respectively, and of the remaining 203 patients, another 10 patients did not answer the Mod QoR-40 on at least two occasions. Ultimately, 193 patients were available for study (Table 1). In addition, 168 patients answered at least some items in the Mod QoR-40 (and Big Five) on every occasion (168 out of 248, 68%), and 143 out of 248 patients (58%) answered all dimensions on all occasions.
Individual differences as regards the five traits were fairly small, with the coefficient of variation (mean/SD) averaging 11%. We found no differences between sexes in any of the five traits (Table 1).
Quality of recovery
Similar to the larger population , the quality of recovery increased significantly for both sexes from day 1 to days 7 and 14 in all dimensions (average trends were significantly greater than zero; P ≤ 0.004; Student's paired t test for men and women separately). Men had lower values of the trends in all traits, but this difference was statistically significant only for ‘physical comfort’, ‘physical independence’ and ‘general health’ (Student's unpaired t test; P < 0.01).
Relationships between personality traits and sex, age, smoking and ASA status
Table 1 presents mean values for the Big Five. No significant differences were found in personality traits between men and women or between smokers and nonsmokers. Patients with ASA I had higher mean scores for ‘agreeableness’ (31.7) than ASA II patients (30.6), P = 0.028 (Mann–Whitney U test). We did not find this in the other personality traits.
Relationships between personality traits and quality of recovery
We found no significant correlations between any of the Big Five personality parameters and the Mod QoR-40 on day 1 (including pain and general health) or the current recovery score obtained on day 14. There were few convincing correlations between the Big Five personality score and the change in any of the dimensions of Mod QoR-40, including pain and general health. The two highest correlations involved changes in ‘physical independence’ in the Mod QoR-40 from day 1 to 7 and ‘extroversion’ (r = 0.20; n = 172; P = 0.010) and ‘openness’, respectively (r = 0.18; n = 167; P = 0.021). All these correlations disappeared completely, however, by day 14 (P > 0.30 comparing day 1 with day 14 on all three occasions). As concerns the difference between days 7 and 14, we found possible negative correlations between ‘physical independence’ on the one hand and ‘agreeableness’ and ‘conscientiousness’ on the other (r = −0.17; n = 158; P = 0.028–0.030 for both).
To further elucidate whether true and time-consistent relationships really exist between personality and postoperative recovery, we used a three-point linear regression to calculate trends in Mod QoR-40 over the 14-day recovery period for each patient and each dimension. These trends, expressed in change per day, showed a relatively good normal distribution. However, we found no significant correlations between personality traits and these trends in Mod QoR-40 (P varying between 0.08 and 0.96; Spearman's rank regression).
The results of our study show that there are some, although minor, relationships between personality traits and the quality of postoperative recovery after day surgery. These relationships were observed in only a single dimension of quality of recovery, that is, ‘physical independence’, which correlated with the personality traits ‘extroversion’ and ‘openness’ on postoperative days 1 and 7. ‘Extroversion’ means energy, positive emotions and the tendency to seek stimulation and the company of others, and ‘openness’ means appreciation for art, emotions, adventure, unusual ideas, imagination, curiosity and a variety of experience [11,17–19]. Hence, extroverted and open individuals seem to experience more ‘physical independence’, that is, to be able to return to work or resume usual home activities such as washing, brushing teeth and shaving. The ‘physical independence’ dimension also correlated with ‘agreeableness’ and ‘conscientiousness’ in changes between postoperative days 7 and 14. ‘Conscientiousness’ means a tendency to show self-discipline, act dutifully and aim for achievement (planned rather than spontaneous behaviour), whereas ‘agreeableness’ means a tendency to be compassionate and cooperative rather than suspicious and antagonistic towards others [11,17–19]. All these correlations seem to be logical. However, as mentioned above, correlations were minor and variation in the Big Five among individuals was small, indicating a homogenous population.
Surprisingly, we found no correlation between the ‘emotional state’ dimension in Mod QoR-40 and any of the personality factors in the Big Five, not even in ‘emotional stability’. A fundamental personality trait in psychology is ‘emotional stability or neuroticism’. It has been defined as an enduring tendency to experience negative emotional states. Low scores indicate that the individual is more likely than the average person to experience feelings of anxiety, anger and guilt and to interpret ordinary situations as threatening and minor frustrations as hopelessly difficult. Individuals with high scores are more emotionally stable and less reactive to stress [11,17–19]. Our study found the mean score for ‘emotional stability’ (Big Five) to be high, as were the scores for the ‘emotional state’ dimension (Mod QoR-40), indicating that the participants were emotionally stable . However, it is reasonable to assume that an inclusion criterion for day surgery would be that the patient is emotionally stable.
Most of the patients (72%) were classified as ASA physical status I. These patients had a significantly higher mean score of ‘agreeableness’ than patients classified as ASA II. Being an inpatient would imply a lower physical status, that is, a higher proportion of ASA scores of more than I. Hence, it is possible that personality differs between inpatients and day surgery patients. Furthermore, can the patient's personality play a greater role, that is, in correlation with the patient's quality of postoperative recovery? This question needs to be explored in greater detail.
The results of this study did not show any relationships between personality traits and sex. Earlier cross-cultural research has shown a universal pattern of gender differences in personality traits, in which women report higher levels of ‘emotional stability’ and ‘agreeableness’ than men across nations. Higher levels of ‘extroversion’ and ‘conscientiousness’ were also reported in women. Surprisingly, gender differences in personality traits were greater in prosperous, healthy and egalitarian cultures in which women have more opportunities that are equal to those of men [20,21]. It has also been found that emotional stability is negatively related to relationship satisfaction in married and dating couples .
Earlier, studies with long-term follow-up of inpatients have shown a relationship between personality traits and well being after coronary bypass surgery  and in health and distress after surgery for ulcerative colitis . However, the personality scale used in the present study, Big Five, differs from the two studies mentioned above. Big Five, developed by Saucier , is proclaimed to be easy to administer . To minimize any distress to preoperative patients experiencing anxiety and pain, it is essential that a patient-based outcome measure should be acceptable to patients and easy to administer. Acceptability has been described as ‘a description of the speed of completion of the questionnaire and the proportion of patients who find it difficult, impossible, or unacceptable for any reason’ . The acceptability of the Big Five can be discussed as some of the participants in our study said that they thought it was difficult to rate the degree of agreement of their personality with some of the descriptive adjectives, for example, ‘unimaginative’ 1–5 (‘not at all’ to ‘extremely’). Others commented on the number of adjectives, the time for rating and the occasion. Perhaps the results would have been different if the patients had completed this assessment at home, the day before surgery, although the time between arriving at the day surgery department and the start of anaesthesia or surgery was short. This could have been experienced as stressful for the patient and might have influenced their responses. However, personality traits do not change easily, or, if they change, they change slowly or after special interventions such as psychotherapy [7,11].
The Mod QoR-40 scale has been found to be acceptable and useful in assessing the quality of recovery up to 14 days in day surgery patients, and it demonstrates sensitivity to change . A recent systematic review  aimed at identifying instruments to measure postoperative quality of recovery outcomes within 1 week after day surgery – to advise on the selection of appropriate measures for research and quality assurance – found that the QoR-40 was the only instrument that fulfilled the criteria.
In day surgery patients, we found minor relationships between personality traits and the quality of recovery. This was observed in ‘physical independence’, which correlated with ‘extroversion’ and ‘intellect’ and with ‘agreeableness’ and ‘conscientiousness’. Also, day surgery patients appear to be a homogenous group with a stable personality, indicating that they have a disposition towards being sociable, task-orientated, considerate of others, active, energetic, experience minor distress and anxiety, have goal-directed behaviour, and have a receptive orientation towards varied experiences and ideas. However, studies need to further explore whether personality traits are related to the quality of postoperative recovery in inpatients and day surgery patients and whether personality differs between inpatients and day surgery patients.
The Health Research Council in Southeast Sweden supported this research, with additional support from the Kalmar County Council, Linköping University, and The Research Committee of Örebro County Council.
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