## 3 Results
### Predictors of Sleep Disturbances  
The stepwise linear regression results concerning the dependent variable sleep disturbance in each data collection moment allowed us to identify the predictors: shift type, trunk flexion, work seniority, horizontal trust, social support from colleagues and auto-efficacy in 2017 (\(F\)(9284) = 10.111, \(p\)\(<\) 0.001; \(R^{2}\) = 0.243 and adjusted \(R^{2}\) = 0.219); shift type and trunk rotation in 2019 (\(F\)(5284) = 11.315, \(p\)\(<\) 0.001; \(R^{2}\) = 0.166 and adjusted \(R^{2}\) = 0.151). The multiple linear regression model results are shown in Table 7. \begin{table}
\begin{tabular}{l c c c c c c} \hline
**2017** & **SoWD (n = 82)** & \multicolumn{3}{c}{**WaSaD (n = 212)**} & \multicolumn{3}{c}{**Shift Type Effect**} \\ \hline  & **Fixed Night** & **Fixed Early** & **Fixed Daytime** & **Rotating (n = 86)** & **Total (n = 294)** & **\(F\)** & \(p\)** \\ \hline General health \(\lx@sectionsign\) & 3.24 (0.71) & 3.29 (0.65) & 2.95 (0.69) & 3.07 (0.75) & 3.07 (0.71) & 3.370 \({}^{\text{a,b}}\) & 0.019 \({}^{\text{*}}\) \\ \hline Sleep disturbances \(\lx@sectionsign\) & 3.58 (1.08) & 3.09 (1.03) & 2.36 (0.93) & 2.40 (0.92) & 2.63 (1.05) & 19.100 \({}^{\text{a,c}}\) & \textless{0.001 \({}^{\text{*}}\)} \\ \hline Fatigue perception & 6.55 (1.28) & 6.82 (1.32) & 7.10 (1.28) & 7.17 (1.47) & 7.01 (1.36) & 2.276 \({}^{\text{a}}\) & 0.080 \\ \hline
**2019** & **SoWD (n = 94)** & \multicolumn{3}{c}{**WaSaD (n = 196)**} & \multicolumn{3}{c}{**Shift type effect**} \\ \hline  & **Fixed night** & **Fixed early morning** & **Fixed daytime** & **Rotating (n = 79)** & **Total (n = 290)** & **\(F\)** & \(p\)** \\ \hline General health \(\lx@sectionsign\) & 2.61 (1.23) & 2.07 (1.23) & 2.38 (1.04) & 2.38 (1.09) & 2.35 (1.12) & 1.602 \({}^{\text{d}}\) & 0.193 \\ \hline Sleep disturbances \(\lx@sectionsign\) & 3.46 (1.04) & 3.03 (1.00) & 2.36 (0.92) & 2.46 (0.91) & 2.66 (1.02) & 14.801 \({}^{\text{d,e}}\) & \textless{0.001 \({}^{\text{*}}\)} \\ \hline Fatigue perception & 3.67 (0.89) & 2.97 (1.06) & 2.35 (0.92) & 2.46 (0.92) & 2.67 (1.04) & 22.256 \({}^{\text{d,f}}\) & \textless{0.001 \({}^{\text{*}}\)} \\ \hline \end{tabular}  
* ANOVA. \({}^{\text{b}}\) [PERSON] multiple comparisons test showed significant differences between fixed early morning and fixed daytime shift types (\(p\) = 0.027). \({}^{\text{*}}\) [PERSON] multiple comparisons tests showed significant differences between fixed night and fixed daytime, fixed night and rotating, fixed early morning and fixed daytime, and fixed early morning and rotating shift types (\(p\) = 0.001 in all comparisons). \({}^{\text{d}}\) ANOVA with Welch correction. \({}^{\text{e}}\) Games–Howell multiple comparisons tests showed significant differences between fixed night and fixed daytime (\(p\) \(<\) 0.001), fixed night and rotating (\(p\) \(<\) 0.001), fixed early morning and fixed daytime (\(p\) \(<\) 0.001), and rotating shift types (\(p\) = 0.0005). \({}^{\text{f}}\) Games–Howell multiple comparisons tests showed significant differences between fixed night and early morning (\(p\) = 0.0005), fixed night and rotating (\(p\) \(<\) 0.001), fixed early morning and fixed daytime (\(p\) \(<\) 0.001), fixed early morning and fixed daytime (\(p\) \(<\) 0.001), fixed early morning and fixed daytime (\(p\) = 0.0002) (There were no significant differences in fatigue perception between the two WaSaD shift types). \({}^{\text{g}}\) COPSQQ scales where the higher value is unfavorable. \({}^{\text{*}}\)\(p\)\(<\) 0.05.  
\end{table} 
Table 6: Mean (SD) for general health, fatigue perception and sleep disturbances variables in 2017 and 2019 by shift type and shift types comparisons.