Table 3

Final three-level models for outcomes (perceived stress and fatigue) using a stepwise approach with AIC criterion

	Stress (PSS-10) (n=2422)*			Fatigue (Pichot) (n=2431)*
	Estimates	CI	P value	Estimates	CI	P value
Fixed effects†
Time	−0.00	−0.16 to 0.16	0.957	0.48	0.31 to 0.66	<0.001
Interviewer (ref=1 (for hospitals A and C))
2 (for hospitals B and D)	1.62	0.85 to 2.40	<0.001	−0.36	−1.47 to 0.76	0.531
HCW-level variables
Gender (ref=female)
Male	−0.83	−1.73 to 0.06	0.068	−1.52	−2.63 to −0.40	0.008
Age (ref=<25)
26–35				1.26	0.09 to 2.44	0.035
36–45				0.50	−0.79 to 1.78	0.450
46–55				−1.01	−2.37 to 0.35	0.147
>55				−2.83	−4.49 to −1.17	0.001
Commuting time to work (ref=>1 hour)
>2 hour				1.82	0.80 to 2.83	<0.001
1 hour–2 hours				0.30	−0.37 to 0.96	0.382
Personal life event (ref=no)
Yes, negative	2.27	1.81 to 2.74	<0.001
Yes, positive	0.46	−0.19 to 1.12	0.164
Professional life event (ref=no)
Yes, negative	1.62	1.11 to 2.12	<0.001
Yes, positive	0.40	−0.34 to 1.14	0.289
Break cancelled due to work overload (ref=never)
Almost never	1.04	0.27 to 1.82	0.008
Quite often	1.54	0.77 to 2.32	<0.001
Very often	1.78	0.92 to 2.65	<0.001
Professional status (ref=temporary CDD)
Contract (contractuel CDI)				2.23	−0.53 to 4.99	0.114
Permanent (titulaire)				0.45	−1.04 to 1.93	0.554
Knowing work schedule in advance (ref=never)
Sometimes	−2.30	−4.81 to 0.22	0.074
Always	−1.87	−4.23 to 0.49	0.121
Support from colleagues—Karasek subscale	−0.12	−0.24 to −0.01	0.035
Support from supervisor—Karasek subscale	−0.23	−0.33 to −0.13	<0.001	−0.34	−0.45 to −0.24	<0.001
HSOPSC item-1‡ (ref=agree)
Neutral	0.00	−1.01 to 1.02	0.995	0.70	−0.52 to 1.91	0.260
Not agree	0.81	−0.10 to 1.71	0.082	1.76	0.81 to 2.70	<0.001
HSOPSC item-8§ (ref=agree)
Neutral	0.46	−0.58 to 1.51	0.385
Not agree	0.96	0.07 to 1.84	0.034
Work overcommitment—Siegrist subscale	0.71	0.63 to 0.78	<0.001	0.65	0.56 to 0.73	<0.001
Sickness presenteeism (ref=never)
Almost never	0.04	−0.48 to 0.57	0.871	0.63	0.04 to 1.22	0.037
Quite often	1.04	0.45 to 1.63	0.001	2.48	1.82 to 3.15	<0.001
Very often	1.61	0.55 to 2.66	0.003	4.03	2.84 to 5.22	<0.001
Ward-level variables
Specialty (ref=surgery/obstetrics)
Other medical specialties¶	−0.36	−1.30 to 0.59	0.459	1.59	0.24 to 2.94	0.021
ICU/reanimation	−1.08	−2.01 to −0.15	0.023	−0.24	−1.60 to 1.13	0.733
Number of beds per ward	−0.03	−0.05 to −0.01	0.009	−0.04	−0.07 to −0.00	0.024
Going outside the ward (ref=never)
Sometimes	1.28	−0.87 to 3.43	0.243	0.98	−2.09 to 4.04	0.533
Often	1.53	−0.70 to 3.76	0.178	0.86	−2.30 to 4.03	0.592
Always	1.87	−0.44 to 4.18	0.112	2.59	−0.70 to 5.89	0.123
Use of interim nurses (ref=never)
Sometimes	0.05	−0.81 to 0.91	0.915	−0.36	−1.59 to 0.88	0.571
Often	0.96	−0.14 to 2.06	0.088	1.96	0.35 to 3.56	0.017
Random effects *
Level 1—time	17.80 (4.23)			22.04 (4.69)
Level 2—healthcare worker	12.30 (3.51)			19.69 (4.44)
Level 3—ward	0.00 (0.00)			0.50 (0.70)
Marginal R²/Conditional R²**	0.507/NA			0.299/0.634
AIC	14 743.16			15 433.57

*The slightly different samples for each outcome refer to the difference between the factors included in the final model for each outcome, following the variable selection. Indeed, the number of missing values per variable has an impact on the number of observations that will be considered in the final mode.
†In multilevel models, fixed effects are usually equivalent to the regression coefficients, while random effects usually account for the underlying structure of the data and characterised by estimates of variability σ²(σ). Fixed effects can be interpreted as slopes in the traditional sense.
‡HSOPSC item-1: item-1 from the Hospital Survey on Patient Safety Culture. ‘Hospital management provides a work climate that promotes patient safety’.
§HSOPSC item-8: item-8 from the Hospital Survey on Patient Safety Culture. ‘The actions of hospital management show that patient safety is a top priority’.
¶The marginal R² considers only the variance of the fixed effects, while the conditional R² takes both the fixed and random effects into account.
AIC, Akaike information criterion; CDD, Fixed-term contract; CDI, Permanent employment contract; HCW, healthcare worker; ICC, intra-class correlation coefficient; ICU, intensive care unit; PSS-10, Perceived Stress Scale 10-item scale.