Basic attributes of female shift nurses
The mean age of the participating nurses was 25.0 (range = 21.0–40.0). In terms of religion, the largest group (48.8%) was not religious. The vast majority of the participants (95.1%) were either single or divorced. Most (70.7%) had a bachelor’s degree or higher. With regard to years of service, the largest group (43.9%) have worked for 1–3 years (Table 1).
Table 1
Basic information of shift nurses (N = 41)
Characteristics | n | Value (%) |
Religion | | |
None | 20 | 48.8 |
Buddhism / Taoism | 17 | 41.5 |
Christianity / Catholicism | 4 | 9.8 |
Marital status | | |
Married | 2 | 4.9 |
Single or divorced | 39 | 95.1 |
Educational background | | |
Junior college | 12 | 29.3 |
University or above | 29 | 70.7 |
Years of service | | |
1–3 years | 18 | 43.9 |
3–5 years | 9 | 22.0 |
5–7 years | 8 | 19.5 |
Over 7 years | 6 | 14.6 |
| Median | Range |
Age (years) | 25 | 21–40 |
CAR differences among shifts
The CARi values of the nurses in morning, evening, and night shifts were 8.04 ± 4.26, 7.49 ± 4.28, and 4.83 ± 3.60. An ANOVA revealed CARi differences among different shifts (F(2, 120) = 7.13, p = .001). Figure 2 presents the CARi trends in the nurses working different shifts.
Level-1 (intraindividual) variance of the CARi, cortisol levels upon waking, and cortisol levels 30 minutes after waking was 12.42, 4.91, and 15.75, respectively, whereas Level-2 (interindividual) variance was 5.87 (p < .05), 5.71 (p < .001), and 15.45 (p < .001), respectively. For the different shifts, the ICCs were 0.3208, 0.5379, and 0.4952, respectively, all higher than the threshold of 13.8% for high correlation25). This means that the interclass differences among the nurses of different shifts in CARi, cortisol levels upon waking, and cortisol levels 30 minutes after waking cannot be ignored and that cross-level analysis is necessary [26]. Thus, a respective 32.08%, 53.79%, and 49.52% of the total variance in CARi, cortisol levels upon waking, and cortisol levels 30 minutes after waking are caused by interindividual variance.
As shown in Table 2, significant differences existed between the CARi of night-shift nurses and that of day-shift nurses (B = -3.41, p < .001), and between the CARi of night-shift nurses and evening-shift nurses (B = -2.92, p < .01), indicating that night-shift nurses exhibited significantly lower CARi than did day-shift nurses or evening-shift nurses. The other variables did not have a significant impact on CARi and no variables were shown to have a significant impact on cortisol levels upon waking, whereas significant differences existed for cortisol levels 30 minutes after waking between night-shift nurses and day-shift nurses (B = -3.88, p < .001), and between night-shift nurses and evening-shift nurses (B = -3.31, p < .01), indicating that night-shift nurses exhibited significantly lower cortisol levels 30 minutes after waking than did day-shift nurses or evening-shift nurses. The other variables did not have a significant impact on cortisol levels 30 minutes after waking.
Table 2
Influence of study variables on CAR (N = 41)
Independent variables | CARi | Cortisol levels upon waking | Cortisol levels 30 minutes after waking |
Fixed effect | | | |
Level 1 | | | |
Intercept | 11.02 | 3.96 | 15.16* |
Shift | | | |
Evening vs day | -0.50 | -0.06 | -0.56 |
Night vs day | -3.41*** | -0.52 | -3.88** |
Night vs evening | -2.92** | -0.45 | -3.31** |
Work stress | | | |
Personal reactions | -0.02 | 0.01 | -0.01 |
Work concerns | -0.01 | -0.01 | -0.02 |
Work competence | 0.01 | -0.03 | -0.02 |
Inability to complete personal tasks | 0.07 | 0.09 | 0.15 |
Level 2 | | | |
Age | -0.18 | -0.01 | -0.19 |
Religion | | | |
Buddhism / Taoism a | 0.38 | 0.53 | 0.93 |
Christianity / Catholicism a | 0.24 | -0.67 | -0.42 |
Marital status (Single or divorced) b | 0.99 | 3.22 | 4.22 |
Educational background (University or above) c | 1.19 | 0.53 | 1.74 |
Years of service | | | |
3–5 years d | -0.57 | 0.77 | 0.20 |
5–7 years d | 0.14 | 0.44 | 0.56 |
Over 7 years d | 0.33 | -0.09 | 0.19 |
Random effect | | | |
Level 2 (Variance component between groups) | 8.84** | 6.03** | 18.99** |
Level 1 (Variance component within group) | 9.99*** | 5.03*** | 13.11*** |
*p < .05; **p < .01; ***p < .001 |
a Religion as the reference group |
b Married as the reference group |
c Junior college as the reference group |
d 1–3 years of service as the reference group |
Work stress differences among shifts
The work stress scores of the nurses in morning, evening, and night shifts were 113.41(SD = 64.35), 119.17(SD = 58.94), and 125.46(SD = 57.72), respectively. An ANOVA revealed no significant differences in work stress among the nurses working different shifts.
Level-1 (intraindividual) variance of the work stress of the female shift nurses was 843.93, while Level-2 (interindividual) variance was 2815.89 (p < .001). The ICC was 0.7694, indicating that differences in work stress among the nurses of different shifts cannot be ignored and that 76.94% of the total variance is caused by interindividual variance.
As can be seen in Table 3, the regression coefficients of all of the variables did not reach the level of significance in personal reaction and overall work stress. For work concerns, only age (B = -3.25, p < .05) reached the level of significance, indicating that older nurses derived less stress from work concerns. With respect to the inability to complete personal tasks, significant differences existed between night-shift nurses and day-shift nurses (B = 4.39, p < .001), and between night-shift nurses and evening-shift nurses (B = 3.95, p < .001), thus night-shift nurses derived significantly more stress from the inability to complete personal tasks than did day-shift nurses or evening-shift nurses.
Table 3
Influence of research variables on work stress of shift nurses (N = 41)
Independent variables | Personal reaction | Work concerns | Work competence | Inability to complete personal tasks | NSCG total score |
Fixed effect | | | | | |
Level 1 | | | | | |
Intercept | 63.03* | 87.49** | 63.37* | 7.18 | 221.79** |
Shift | | | | | |
Evening vs day | 2.91 | 3.55 | -1.30 | 0.44 | 5.61 |
Night vs day | 5.25 | 1.95 | 0.31 | 4.39*** | 11.91 |
Night vs evening | 2.34 | -1.61 | 1.61 | 3.95*** | 6.29 |
Level 2 | | | | | |
Age | -1.55 | -3.25* | -1.29 | -0.04 | -6.17 |
Religion | | | | | |
Buddhism / Taoism a | 8.86 | 6.93 | 4.53 | 1.57 | 21.88 |
Christianity / Catholicism a | -4.44 | -10.49 | -6.59 | 0.90 | -20.70 |
Marital status (Single or divorced) b | 7.63 | 12.66 | 0.98 | 0.52 | 21.98 |
Educational background (University or above) c | 9.95 | 6.10 | 1.31 | 1.70 | 19.16 |
Years of service | | | | | |
3–5 years d | 8.52 | 8.13 | 2.55 | 0.15 | 19.47 |
5–7 years d | 6.97 | 17.17 | -0.84 | 0.23 | 23.72 |
Over 7 years d | -7.94 | 28.39 | 4.34 | -2.96 | 22.35 |
Random effect | | | | | |
Level 2 (Variance component between groups) | 571.72*** | 345.46*** | 227.96*** | 17.97** | 2930.95*** |
Level 1 (Variance component within group) | 180.57*** | 88.09*** | 121.17*** | 17.16*** | 821.90*** |
*p < .05; **p < .01; ***p < .001 |
a Religion as the reference group |
b Married as the reference group |
c Junior college as the reference group |
d 1–3 years of service as the reference group |
Influence of work stress on CAR
An ANOVA of the stress from personal reactions, work concerns, work competence, and inability to complete personal tasks for nurses working the three different shifts presented no significant differences. With the shift and other personal attributes controlled, the four aspects of work stress also showed no significant differences in their influence on the CARi, cortisol levels upon waking, or cortisol levels 30 minutes after waking of female shift nurses (Table 3).