DOI 10.1007/s00420-011-0730-8
O R I G I N A L A R T I C L E
Atypical work schedules are associated with poor sleep quality
and mental health in Taiwan female nurses
Pei-Chen Lin · Chung-Hey Chen · Shung-Mei Pan · Chih-Hong Pan · Chiou-Jong Chen · Yao-Mei Chen · Hsin-Chia Hung · Ming-Tsang Wu
Received: 12 April 2011 / Accepted: 7 December 2011 © Springer-Verlag 2011
Abstract
Purpose To investigate the eVects of shift work schedules on sleep quality and mental health in female nurses in south Taiwan.
Methods This study recruited 1,360 female registered nurses in the Kaohsiung area for the Wrst survey, and among them, 769 nurses had a rotation shift schedule. Among the 769 rotation shift work nurses, 407 completed another second survey 6–10 months later. Data collection included demographic variables, work status, shift work schedule, sleep quality (Pittsburgh Sleep Quality Index), and mental health (Chinese Health Questionnaire-12). Results Nurses on rotation shift had the poor sleep quality and mental health compared to nurses on day shift.
The nurses on rotation shift had a relatively higher OR of reporting poor sleep quality and poor mental health (OR, 2.26; 95% CI, 1.57–3.28; and OR, 1.91; 95% CI, 1.39– 2.63, respectively). Additionally, rotation shift nurses who had ¸2 days oV after their most recent night shifts showed signiWcantly improved sleep quality and mental health (PSQI decreased of 1.23 and CHQ-12 decreased of 0.86, respectively). Comparison of sleep quality between the Wrst and second surveys showed aggravated sleep quality only in nurses who had an increased frequency of night shifts.
Conclusion Female nurses who have a rotation shift work schedule tend to experience poor sleep quality and mental health, but their sleep quality and mental health improve if
P.-C. Lin · M.-T. Wu
Graduate Institute of Occupational Safety and Health, Kaohsiung Medical University, Kaohsiung, Taiwan
e-mail: pei401@gmail.com
P.-C. Lin
Research and Training, Kaohsiung Municipal Hsiao-Kang Hospital, Kaohsiung, Taiwan
C.-H. Chen
Institute of Allied Health Sciences and Department of Nursing, National Cheng Kung University, Tainan, Taiwan
C.-H. Chen · Y.-M. Chen
College of Nursing, Kaohsiung Medical University, Kaohsiung, Taiwan
S.-M. Pan
Department of Nursing, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung, Taiwan
S.-M. Pan
Superintendent OYce, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
C.-H. Pan · C.-J. Chen
Institute of Occupational Safety and Health, Council of Labor AVairs, Executive Yuan, New Taipei City, Taiwan
Y.-M. Chen
Department of Nursing, Kaohsiung Municipal Hsiao-Kang Hospital, Kaohsiung, Taiwan
H.-C. Hung (&)
Department of Nursing, Meiho University, 912 No. 23 Pingguang Road, PingTung, Taiwan e-mail: x00002157@meiho.edu.tw
M.-T. Wu (&)
Department of Family Medicine, Kaohsiung Medical University Hospital, 807 100 Shih-Chuan 1st Road, Kaohsiung, Taiwan e-mail: 960021@ms.kmuh.org.tw
M.-T. Wu
Center of Environmental and Occupational Medicine, Kaohsiung Municipal Hsiao-Kang Hospital, Kaohsiung, Taiwan
they have ¸2 days oV after their most recent night shifts. This empirical information is useful for optimizing work schedules for nurses.
Keywords Shift work · Nurses · Pittsburgh Sleep Quality Index (PSQI) · Chinese Health Questionnaire-12 (CHQ-12)
Introduction
Night shift work is common and is an essential work rotation for nurses since patients in hospitals need 24-hour care. Hence, the detrimental eVect of working a night shift is an important occupational hazard of nurses. Working a night shift can aVect the sleep/wake cycle by disrupting the synchronous relationship between the nat-ural circadian rhythm of the body and the environment. Studies show that at least 75% of shift workers are aVected by sleep disturbance (Akerstedt et al. 2008) and 32.1% of night and 26.1% of rotating shift workers have insomnia or excessive sleepiness (Drake et al. 2004). Compared to nurses who work day shifts, those work rotation shifts and Wxed night shifts are 2.82 and 1.80 times more likely to have poor sleep quality, respectively (Gold et al. 1992).
Shift work can also adversely aVect psychological health and well-being. A night shift work schedule is associated with increased risk of poor mental health and anxiety/ depression (Bara and Arber 2009). One study demonstrated that 69.8% of nurses who worked night shift and rotation shift had poor mental health, whereas only 55.6% of those who worked day shift had poor mental health (Suzuki et al. 2004).
Since poor sleep quality and mental health of nurses can adversely aVect the patient treatment, (Gold et al. 1992; Suzuki et al. 2004; Arimura et al. 2010), eVectively arrang-ing shift schedules to attenuate the eVects of rotation work schedules among health workers is essential. Although the eVects of shift work schedules have been studied in other occupations (Rosa and Colligan 1997; Knauth and Hornberger 2003), few studies have discussed the eVects of rotation shift work schedules in nurses (Wilson 2002; Ber-ger and Hobbs 2006), and no studies have provided evi-dence-based information about the optimal and appropriate rotation shift work. Thus, in addition to examine whether night shift work adversely aVects sleep quality and mental health, this study also compared diVerent night shift sched-ules in terms of their eVects on sleep quality and mental health. The objective was to determine the suYcient amount of rest needed after a night shift and reduction in night shifts needed to attenuate the detrimental eVect of night shift work.
Methods Study population
The potential study subjects were female registered nurses aged 20–45 years old in the Kaohsiung metropolitan area of southwestern Taiwan, which included Kaohsiung city and county. This study was approved by the Kaohsiung Nursing Association and Internal Review Board of Kaohsiung Medical University Hospital (KMUH-IRB-940086).
Two of the strategies recommended by Kaohsiung City and Kaohsiung County Nurse Associations were used to recruit study subjects. First, the nursing department super-visors of seven hospitals (two medical centers and Wve regional/district hospitals) in Kaohsiung city were willing to assist in distributing informed consent forms to their nurses. Of the total number of consent forms distributed, 882 signed informed consent forms were retrieved by July, 2005. A self-administrated structured questionnaire was then mailed to 882 nurses who gave consent to the study and 456 (51.7%) responded.
The name and address of the remaining 7,173 nurses were then obtained from the Kaohsiung City and County Nurse Association. Of the 7,173 self-administrated struc-tured questionnaires and informed consent forms mailed, 1,030 (14.4%) signed informed consent forms and com-pleted questionnaires were retrieved from July 2005 to October 2005.
In April 2006, 776 follow-up questionnaires were mailed to those who reported working rotation shift schedules in the Wrst questionnaire information. Of these, 508 (65.5%) responses were retrieved.
Measurement
Demographic variables
Demographic variables included age, marital status, num-ber of children, duration of employment, and medical cen-ter (yes or no). Compared to men, women in Chinese populations tend to assume more responsibilities for family care even though they have their own jobs. Thus, the vari-ables of marital status and number of children may con-found the relation between nursing works and sleep quality and mental health. In addition, data regarding hospital size and duration of employment were also collected, because they were probably related to physical and mental load.
Shift schedule and shift work arrangement
Workplace and work schedule were evaluated by ques-tionnaires, and shift work was divided into three main work
schedules: day shift, non-night shift, and rotation shift. A non-night shift was deWned as a shift ending before mid-night. Rotation shift was deWned as a work schedule that included the day shift (from 8 AM to 4 PM), evening shift (from 4 PM to 12 midnight or from 2 PM to 10 PM), and night shift (from 12 midnight to 8 AM).
Nurses who worked rotation shift were asked three fur-ther questions about their work schedule: 1. How frequently did your shift change in the last 2 months?; 2. How many days oV did you receive when you switched from the night shift to other shifts?; 3. In the last 2 months, how many night shifts did you work?
Sleep quality
Sleep Quality was measured by Pittsburgh Sleep Quality Index (PSQI), which measures self-reported sleep habits over the last month (Buysse et al. 1989). The Index measures seven components using nineteen individual items. The total score ranges from 0 to 21. To Wt the characteristic of sleep pattern in the study population, the original questions “When have you usually gone to bed at night?” and “When have you usually gotten up in the morning?” were modiWed as “How long have you slept between going to bed and getting up?” Higher scores reXected poorer overall sleep quality. A previ-ous study of primary insomniacs and healthy controls in community-dwelling adults reported that the cutoV score of 5 in the Chinese version PSQI has a sensitivity and speciWcity of 98 and 55%, respectively (Tsai et al. 2005).
Mental health
The Chinese Health Questionnaire 12-item (CHQ-12) was used to evaluate the mental health status. The CHQ-12 was translated from General Health Questionnaire (GHQ) and modiWed by adding culturally relevant items (Cheng and Williams 1986). The 12-item self-rated CHQ-12 was designed to assess nonorganic and nonpsychotic mental disorder in a population. The total score ranged from 0 to 12 where a higher total CHQ-12 score indicated worse mental health. The optimal cutoV point was 3/4 by relative operating characteristic (ROC) analysis (Chong and Wilkinson 1989). The sensitivity and speciWcity of CHQ-12 were 77.8 and 76.9%, respectively; therefore, only scores ¸4 score were considered indicators of poor mental health (Chong and Wilkinson 1989).
Statistical analysis
Of the 1,486 questionnaires received, 45 questionnaires were excluded because they did not provide shift schedule information, and 81 were excluded because they did not provide suYcient information to calculate of PSQI or/and
CHQ-12 scores. The remaining 1,360 nurses were recruited for the Wnal analysis.
Among the 508 questionnaires received in the second survey, 17 were excluded because the respondent quit the job, 33 were excluded because the respondent transferred to day shift. Another 13 were excluded because they did not provide suYcient information to calculate PSQI or/and CHQ-12 scores. The remaining 445 questionnaires were then merged with the 769 questionnaires received from respondent who worked rotation shift according to the Wrst survey. After excluding 38 incomplete questionnaires from Wrst survey, the second phase of the study analyzed 407 participants.
The participants were categorized by shift work sched-ules as day shift, non-night shift, and rotation shift. Demo-graphic variables, sleep quality, and mental health were compared among these three groups using Chi-squared test and ANOVA (analyses of variances) test. SigniWcant demo-graphic variables observed in the univariate analysis, including age, duration of employment, marital status, number of children, and medical center (yes or no), were included in the multivariate models. Analysis of covariance (ANCOVA) tests were used to compare the three groups after adjusting for other factors on the sleep quality and mental health. Linear and logistic regression models were further used to adjust for potential confounding factors.
For those who worked rotation shift, the adjusted mean (SE, standard error) of the sleep quality and mental health was described in the shift arrangement variables (frequency of shift change, number of days oV after night shift and cumula-tive night shift days), and these shift arrangement variables were compared separately after ANCOVA tests of demo-graphic factors. Chi-squared test of PSQI categories and CHQ-12 categories across the shift arrangement variables and the regression analyses were performed to examine the inde-pendent eVect of groups on the PSQI and CHQ-12 scores.
Changes in sleep quality and mental health scores were further compared between the primary and secondary sur-veys using paired t test stratiWed by groups with unchanged, increased, and decreased frequency of night shifts in the last two months between these two surveys. The JMP 8.0 for Windows was used to perform all the statistical analy-ses, and the signiWcance level (P value) was set to 0.05. Results
The mean age of the 1,360 participants was 29.9 years, and 56.5% of the subjects worked rotation shift. More than one-half of the nurses in the rotation shift were younger than 30 years (58.4%), were single (67.5%), and had no children (72.7%), and these proportions signiWcantly diVered from day shift and non-night shift workers (Table1).
Sleep quality and mental health were signiWcantly worse in the rotation shift (adjusted mean PSQI, 8.99; adjusted mean CHQ-12, 4.98) than in other work schedules after adjusting for age, duration of employment, marital status, number of children, and medical center (yes vs. no) (Table2). Compared to nurses who worked day shift, the average PSQI and CHQ-12 scores signiWcantly increased (1.59 and 0.72, respectively) in nurses who worked rotation shift after adjusting for confounding factors (Table2).
At cut-points of >5 in PSQI and ¸4 in CHQ-12, 78 and 58% of the study participants had poor sleep quality and men-tal health, respectively. The percentages of poor sleep quality and mental health were even higher in nurses on rotation shift (84.3 and 65.9%) (Table3). After adjusting for other covari-ates, nurses who worked rotation shift had a 2.26-fold (95% CI = 1.57–3.28) higher risk of poor sleep quality and a 1.91-fold (95% CI = 1.39–2.26) higher risk of poor mental health compared to nurses who worked day shift.
Among the 769 rotation shift nurses, average PSQI and CHQ-12 were signiWcantly decreased in those who had received ¸2 days oV after the last night shift than in those who had received 1 day oV (Table4). The poor sleep qual-ity and mental health were also ameliorated in the group of nurses with ¸2 days oV after their last night shift compared to those with 1 day oV since their last night shift. However, only the amelioration of poor mental health reached to be statistically signiWcant (Table5). In addition, the more days of night shift in the 2 months, the higher averaged PSQI scores were found (Table4).
In the 407 nurses on rotation shift, PSQI scores did not sig-niWcantly diVer between the Wrst and second surveys (paired t test, P value = 0.6374). However, in the group of nurses who indicated that their night shift had increased between the Wrst and second surveys, PSQI scores had signiWcantly increased by 0.82 between the Wrst and second surveys (Table6). In contrast, all mean CHQ-12 scores signiWcantly increased
Table 1 Demographic characteristics by diVerent work schedule among the 1,360 nurses
SD standard deviation, Single unmarried and divorced
PSQI Pittsburgh Sleep Quality Index, CHQ-12 Chinese Health Questionnaire-12
Day shift Non-night shift Rotation shift P value
N % Mean § SD N % Mean § SD N % Mean § SD
Age 288 303 769 20–24 16 5.6 82 27.4 255 34.2 <0.0001 25–29 63 22.0 110 37.8 194 26.0 30–34 81 28.3 43 14.4 123 16.5 35–39 91 31.8 48 16.1 61 8.2 40–45 35 12.2 16 5.4 13 1.7 Missing 2 4 23 Years of employment <0.0001 <2 8 2.8 28 9.2 172 22.4 2–4 14 4.9 75 24.8 138 17.9 5–9 75 26.0 94 31.0 274 35.6 ¸10 191 66.3 106 35.0 185 24.1 Marital status <0.0001 Single 91 31.6 156 51.5 519 67.5 Married 197 68.4 147 48.5 250 32.5 Number of children <0.0001 0 114 39.6 170 56.3 559 72.7 1 42 14.6 45 14.9 87 11.3 ¸2 132 45.8 87 28.8 123 16.0 Missing 1 Medical center <0.0001 Yes 65 22.6 54 17.8 336 43.8 No 223 77.4 249 82.2 432 56.3 Missing 1
Sleep quality (PSQI) 7.32 § 3.49 7.20 § 3.27 9.04 § 3.55 <0.0001
Table 2 Scores of PSQI (Sleep quality) and CHQ-12 (mental health) categorized by work schedules using ANCOVA and multiple regression
statistics among the 1,360 nurses
a SigniWcant statistic in the comparison of day shift versus rotation shift
b SigniWcant statistic in the comparison of shift without night versus rotation shift
c Adjusting for age (years), duration of employment, marital status, number of children, and medical center (yes or no)
LSMean Least square mean; SE standard error
PSQI Pittsburgh Sleep Quality Index, CHQ-12 Chinese Health Questionnaire-12
PSQI CHQ-12
LSMeanc§SE P value (se)c P value LSMeanc§SE P value (se) P value
Work schedule <0.0001a, b <0.0001a, b
Day shift 7.40 § 0.22 Reference 4.26 § 0.16 Reference
Non-night shift 7.21 § 0.20 ¡0.19 (0.30) 0.5284 4.19 § 0.15 ¡0.06 (0.22) 0.7889 Rotation shift 8.99 § 0.13 1.59 (0.28) <0.0001 4.98 § 0.10 0.72 (0.20) 0.0003
Table 3 Adjusted odds ratios (AOR) of poor sleep quality (PSQI) and mental health (CHQ-12) among the 1,360 nurses with diVerent work
schedules
a Adjusting for age (years), duration of employment, marital status, number of children, and medical center (yes vs. no)
PSQI Pittsburgh Sleep Quality Index, CHQ-12 Chinese Health Questionnaire-12, CI conWdence interval
PSQI CHQ-12
Poor N (%) Good N (%) P value AORa 95% CI Poor N (%) Good N (%) P value AORa 95% CI
Work schedule <0.0001 <0.0001
Day shift 199 (69.1) 89 (30.9) 1.00 136 (47.2) 152 (52. 8) 1.00
Non-night shift 214 (70.6) 89 (29.4) 1.04 0.71–1.51 150 (49.5) 153 (50.5) 1.00 0.71–1.40 Rotation shift 648 (84.3) 121 (15.7) 2.26 1.57–3.28 507 (65.9) 262 (34.1) 1.91 1.39–2.63
Table 4 Scores of PSQI (sleep quality) and CHQ-12 (mental health) categorized by shift work arrangements using ANCOVA and multiple
regression statistics among the 769 nurses with rotation shift
a SigniWcant statistic in the comparison of · 6 days versus ¸ 15 days in cumulative days of night shift in the 2 months b Adjusting for age (years), duration of employment, marital status, number of children, and medical center (yes or no)
LSMean Least square mean, SE standard error
PSQI Pittsburgh Sleep Quality Index, CHQ-12 Chinese Health Questionnaire-12, CI conWdence interval
PSQI CHQ-12
N LSmeanb§SE P value (se)c P value LSmeanb§SE P value (se)b P value
Shift work arrangement
Period of shift change 0.6462 0.6811
<1 week 500 9.11 § 0.16 Reference 5.09 § 0.12 Reference
¸1 week–<1 month 156 8.78 § 3.20 ¡0.30 (0.34) 0.3699 4.92 § 2.55 ¡0.21 (0.25) 0.3891 ¸1 month 113 9.03 § 0.37 ¡0.10 (0.42) 0.8142 5.02 § 0.27 ¡0.09 (0.31) 0.7753
Day oV after the last night shift <0.0001 0.0001
1 day 586 9.32 § 0.15 Reference 5.24 § 0.11 Reference
¸2 days 183 8.09 § 0.26 ¡1.23 (0.30) <0.0001 4.38 § 0.19 ¡0.86 (0.22) 0.0001 Cumulative days of night
shift in the 2 months
0.0315a 0.6718
·6 days 281 8.61 § 0.22 Reference 4.93 § 0.16 Reference
7–14 days 307 9.13 § 0.20 0.53 (0.30) 0.0798 5.07 § 0.15 0.15 (0.22) 0.4867
between the Wrst and second years regardless of the change in frequency of night shifts (Table6).
Discussion
This study showed that nurses who worked rotation shift appeared to have poorer sleep quality and mental health com-pared to the two other groups those worked without night shift. Of nurses who worked night shift, those with 2 days oV after the last night shift had improved sleep quality and men-tal health. Comparison of the Wrst and second surveys indi-cated that increased frequency of night shifts worsened sleep quality. However, decreased frequency of night shifts appar-ently did not improve sleep quality. In all of these nurses, mental health was worse than that in the previous year.
The night shift nurses in this study had the worst sleep quality (PSQI score: 9.04) compared to those who worked day shift (PSQI score: 7.32) or non-night shift (PSQI score: 7.20). This Wnding is consistent with other studies (Ruggiero 2005; van Mark et al. 2010). Ruggiero reported that nurses who worked a Wxed night shift and rotation shift had higher PSQI scores (7.86 and 7.31, respectively) compared to those who worked day shift (PSQI score, 6.37) (Ruggiero 2005). A study of the general population by van Mark et al. (2010) also reported that shift workers had a signiWcantly higher mean PSQI score compared to day workers (6.73 vs. 4.66) regardless of occupation. In another study that used Epworth Sleepiness Scale (ESS) in a questionnaire survey, Drake et al. (2004) reported that the prevalence of insomnia or excessive sleepiness was 32 and 26% in night and rotation shift workers, respectively, but only 18% in day workers.
Table 5 Adjusted odd ratios (AOR) of poor sleep quality (PSQI) and mental health (CHQ-12) by diVerent shift schedules arrangement among the
769 nurses with rotation shift
a
Adjusting for age (years), duration of employment, marital status, number of children, and medical center (yes vs. no)
PSQI Pittsburgh Sleep Quality Index, CHQ-12 Chinese Health Questionnaire-12, CI conWdence interval
PSQI CHQ-12
Poor N (%) Good N (%) P value AORa 95% CI Poor N (%) Good N (%) P value AORa 95% CI
Shift work arrangement
Period of shift change 0.6740 0.4557
<1 week 419 (83.8) 81 (16.2) 1 336 (67.2) 164 (32.8) 1
¸1 week–<1 month 135 (86.5) 21 (13.5) 1.18 0.70–2.08 102 (65.4) 54 (34.6) 0.92 0.62–1.38 ¸1 month 94 (83.2) 19 (16.8) 0.73 0.38–0.91 69 (61.1) 44 (38.9) 0.66 0.41–1.07 Days oV after the
last night shift
0.0176 0.0374
1 day 504 (86.0) 82 (14.0) 1 398 (67.9) 188 (32.1) 1
¸2 days 144 (78.7) 39 (21.3) 0.58 0.44–1.10 109 (59.6) 74 (40.4) 0.69 0.49–0.98 Cumulative days of night
shift in the 2 months
0.4114 0.8919
·6 days 231 (82.2) 50 (17.8) 1 184 (65.5) 97 (34.5) 1
7–14 days 260 (84.7) 47 (15.3) 1.22 0.77–1.92 201 (65.5) 106 (34.5) 0.94 0.66–1.34 ¸15 days 157 (86.7) 24 (13.3) 1.29 0.75–2.27 122 (67.4) 59 (32.6) 0.96 0.63–1.45
Table 6 The changes of sleep quality (PSQI) and mental health (CHQ-12) between the Wrst and second surveys among the 407 nurses with
rota-tion shift
a Adjusting for baseline number of night shift days
SE standard error
N Pittsburgh Sleep Quality Index Chinese Health Questionnaire-12 First year Second year Mean diVerence §SE
P value (se)a P value First
year Second year Mean diVerence §SE
P value (se)a P value
Change of total days of night shift in second survey
Unchanged 198 8.74 8.50 ¡0.24 § 0.21 0.2571 Reference 4.84 5.25 0.41 § 0.19 0.0296 Reference
Increased 98 8.87 9.68 0.82 § 0.30 0.0070 1.08 (0.38) 0.0042 5.10 5.88 0.78 § 0.28 0.0075 0.43 (0.32) 0.1845 Decreased 111 8.83 8.80 ¡0.03 § 0.30 0.9280 0.13 (0.38) 0.7225 4.86 5.32 0.45 § 0.23 0.0490 ¡0.18 (0.33) 0.5789
A plausible biological explanation for the association between night shift work and sleep quality might be the endogenous signal of darkness, melatonin, which is an important component of the internal timekeeping system (Pandi-Perumal et al. 2008). Melatonin promotes falling asleep and sleep by inhibiting suprachiasmatic nucleus, and the secretion of melatonin is suppressed by light. Hence, alteration of melatonin levels by extended exposure to light could trigger the desynchronicity between the internal hor-monal environment and the external environment, which may explain why nurses who work night shift are suscepti-ble to poor sleep quality.
SuYcient rest after a night shift may also attenuate the disturbance of sleep for nurses with rotating schedules. Internal circadian rhythms adjust very slowly in the sleep/wake cycle, and shift workers can often return to night sleep and daytime activities while their altered sleep/ wake schedule is not maintained long enough to allow suY-cient adaptation (Lamond et al. 2003). Hence, the ergo-nomic recommendation is that at least 2 days oV after the last night for decreasing the reduction in sleep before morn-ing shift (Rosa and Colligan 1997; Knauth and Hornberger 2003; Berger and Hobbs 2006). After a night shift, two days oV are generally recommended on application of shift system, especially in industries. However, no empirical data support that this recommendation is widely observed in nurses who work rotation schedule. This study found that nurses who had 2 or more days oV after night shifts had sig-niWcantly improved sleep quality compared with those who with only one day oV, which supported the general recom-mendation.
Since an increased frequency of night shifts can worse sleep, successive night shifts should be minimized to avoid diYculty adapting to circadian rhythms and to avoid accu-mulation of sleep deWcits. Schernhammer et al. (2004) indi-cated that the number of nights worked within a 2-week period has a signiWcant negative correlation with melatonin level (r = ¡0.30, P = 0.008). In their study, subjects who worked over 4, 1–4, and 0 night shifts within the past 2 weeks had urinary creatinine-adjusted 6-sulfatoxymelato-nin concentration (ng/ml) of 12, 18, and 27, respectively. The results of the current study and follow-up study agreed that the frequency of night shifts within a 2-month period correlated negatively with sleep. Additionally, nurses who had worked an increased number of night shifts between Wrst and second survey had signiWcantly worse sleep qual-ity during the second year compared to the Wrst year, and their average PSQI increased from 8.87 to 9.68 (P value = 0.007). These results suggest that appropriately limiting the frequency of night shift might attenuate their detrimental eVects.
This high stress of shift work may also result in poor mental health if (Conway et al. 2008) social marginalization
(Costa 2003) and family conXict (Fujimoto et al. 2008) because of the shift work decrease satisfaction of physical and psychical needs. Epidemiological and electroencepha-lographic studies also show that sleep disturbance and chronic insomnia are common triggers of depression and as predictors of depressive disorder (Srinivasan et al. 2009). In nurses, deterioration of mental health may be detrimental not only to their own physical health but also to the health of their patients. The previous studies indicate that medical errors correlate negatively with mental health status (Suzuki et al. 2004; Arimura et al. 2010).
This study also showed that the rotation shift group had signiWcantly poorer mental health compared to the other two groups because of their poor sleep quality. Among the nurses in the rotation shift, the CHQ-12 score was better in those who had received at least 2 days oV after since their last night shift than in those who had received only 1 day oV (CHQ-12 score: 4.44 vs. 5.26). Therefore, adequate rest time apparently beneWts both mental health and sleep quality.
The second survey further showed that all nurses in the rotation shift group had signiWcantly worse mental health compared to the previous year, and those with a high fre-quency of shift work seemed to the largest decrease in the mental health. These observations suggest that increased frequency of shift work might be associated with detrimen-tal mendetrimen-tal health. The trend of poor mendetrimen-tal health of all nurses also reXected that nurses are to be in less friendly sit-uations. This is a wake-up alarm for working environment of nurses and quality of patient care. In recent years, hospi-tal accreditation for regional/district hospihospi-tals and the pay-ment system for the National Health Insurance Scheme have increased the work load of nurses in Taiwan. In addi-tion to caring for patients, nurses need to provide docu-ments required for hospital accreditation and docudocu-ments required by the National Health Insurance system. How-ever, a few nurses received formal education and training to perform these additional duties, which may detrimentally aVect their mental health. Further studies of insuYciencies in the training of nurses would help hospital managers and nursing educators recognize and further minimize the impact.
The main limitation of this study is the low response rate. However, the mean ages of respondents in the initial survey performed by Kaohsiung City and County Nurses Association were 30.2 and 29.9 years, respectively, which were similar to the mean ages in this study (30.1 and 29.7 years, respectively). Therefore, we are conWdent that our Wnding can be representative of Kaohsiung area nurses aged 20–45 years.
This study found that female nurses who work rotation shift experience poor sleep quality and mental health and that 2 or more days oV after the last night shift might
improve their sleep quality and mental health. These Wnd-ings provide useful empirical information for arranging shift schedules. To adjust rotation schedules to improve the health of nurses and the care of patients, further interven-tional or longitudinal research is needed to clarify the eVects of diVering shift schedules of nurses. Future studies may consider whether the managers of hospital nursing departments should reconsider the appropriate number of days oV after the last night shift and the appropriate number of consecutive night shifts.
Acknowledgments The authors express their thanks to Kaohsiung County Nurses Association and Kaohsiung City Nurses Association. The project was supported by the Institute of Occupational Safety and Health (No: ISOH95-M318, IOSH96-M318) and the National Science Council (No: NSC97-2314-B-037-018-MY3).
ConXict of interest The authors declare that they have no conXict of
interest.
References
Akerstedt T, Ingre M, Broman JE, Kecklund G (2008) Disturbed sleep in shift workers, day workers, and insomniacs. Chronobiol Int 25(2):333–348. doi:10.1080/07420520802113922
Arimura M, Imai M, Okawa M, Fujimura T, Yamada N (2010) Sleep, mental health status, and medical errors among hospital nurses in Japan. Ind Health 48(6):811–817. doi:JST.JSTAGE/indhealth/ MS1093
Bara AC, Arber S (2009) Working shifts and mental health–Wndings from the British Household Panel Survey (1995–2005). Scand J Work Environ Health 35(5):361–367
Berger AM, Hobbs BB (2006) Impact of shift work on the health and safety of nurses and patients. Clin J Oncol Nurs 10(4):465–471 Buysse DJ, Reynolds CF 3rd, Monk TH, Berman SR, Kupfer DJ
(1989) The Pittsburgh Sleep Quality Index: a new instrument for psychiatric practice and research. Psychiatry Res 28(2):193–213. doi:0165-1781(89)90047-4
Cheng TA, Williams P (1986) The design and development of a screening questionnaire (CHQ) for use in community studies of mental disorders in Taiwan. Psychol Med 16(2):415–422 Chong MY, Wilkinson G (1989) Validation of 30- and 12-item versions
of the Chinese Health Questionnaire (CHQ) in patients admitted for general health screening. Psychol Med 19(2):495–505
Conway PM, Campanini P, Sartori S, Dotti R, Costa G (2008) Main and interactive eVects of shiftwork, age and work stress on health in an Italian sample of healthcare workers. Appl Ergon 39(5):630–639. doi:10.1016/j.apergo.2008.01.007
Costa G (2003) Shift work and occupational medicine: an overview. Occup Med (Lond) 53(2):83–88
Drake CL, Roehrs T, Richardson G, Walsh JK, Roth T (2004) Shift work sleep disorder: prevalence and consequences beyond that of symptomatic day workers. Sleep 27(8):1453–1462
Fujimoto T, Kotani S, Suzuki R (2008) Work-family conXict of nurses in Japan. J Clin Nurs 17(24):3286–3295. doi: 10.1111/j.1365-2702.2008.02643.x
Gold DR, Rogacz S, Bock N, Tosteson TD, Baum TM, Speizer FE, Czeisler CA (1992) Rotating shift work, sleep, and accidents re-lated to sleepiness in hospital nurses. Am J Public Health 82(7):1011–1014
Knauth P, Hornberger S (2003) Preventive and compensatory mea-sures for shift workers. Occup Med (Lond) 53(2):109–116 Lamond N, Dorrian J, Roach GD, McCulloch K, Holmes AL, Burgess
HJ, Fletcher A, Dawson D (2003) The impact of a week of simu-lated night work on sleep, circadian phase, and performance. Oc-cup Environ Med 60(11):e13
Pandi-Perumal SR, Trakht I, Srinivasan V, Spence DW, Maestroni GJ, Zisapel N, Cardinali DP (2008) Physiological eVects of melato-nin: role of melatonin receptors and signal transduction pathways. Prog Neurobiol 85(3):335–353. doi:10.1016/j.pneurobio.2008. 04.001
Rosa RR, Colligan MJ (1997) Plain language about shiftwork Ruggiero JS (2005) Health, work variables, and job satisfaction among
nurses. J Nurs Adm 35(5):254–263. doi: 00005110-200505000-00009
Schernhammer ES, Rosner B, Willett WC, Laden F, Colditz GA, Han-kinson SE (2004) Epidemiology of urinary melatonin in women and its relation to other hormones and night work. Cancer Epi-demiol Biomarkers Prev 13(6):936–943
Srinivasan V, Pandi-Perumal SR, Trakht I, Spence DW, Hardeland R, Poeggeler B, Cardinali DP (2009) Pathophysiology of depression: role of sleep and the melatonergic system. Psychiatry Res 165(3):201–214. doi:10.1016/j.psychres.2007.11.020
Suzuki K, Ohida T, Kaneita Y, Yokoyama E, Miyake T, Harano S, Yagi Y, Ibuka E, Kaneko A, Tsutsui T, Uchiyama M (2004) Men-tal health status, shift work, and occupational accidents among hospital nurses in Japan. J Occup Health 46(6):448–454. doi:JST.JSTAGE/joh/46.448
Tsai PS, Wang SY, Wang MY, Su CT, Yang TT, Huang CJ, Fang SC (2005) Psychometric evaluation of the Chinese version of the Pittsburgh Sleep Quality Index (CPSQI) in primary insomnia and control subjects. Qual Life Res 14(8):1943–1952. doi:10.1007/ s11136-005-4346-x
van Mark A, Weiler SW, Schroder M, Otto A, Jauch-Chara K, Grone-berg DA, Spallek M, Kessel R, Kalsdorf B (2010) The impact of shift work induced chronic circadian disruption on IL-6 and TNF-alpha immune responses. J Occup Med Toxicol 5:18. doi:10.1186/1745-6673-5-18
Wilson JL (2002) The impact of shift patterns on healthcare profes-sionals. J Nurs Manag 10(4):211–219. doi:10.1046/j.1365-2834. 2002.00308.x.
