Cognitive functions of shift workers: paramedics and firefighters – an electroencephalography study

Figures & data

Figure 1. Attention network test pattern. Note: * cue; + fixation point.

Figure 2. N-back task pattern. Note: Left button, matched stimuli; right button, non-matched stimuli.

Table 1. Reaction time to a matched and non-matched stimulus in the N-back task.

	1-Back condition		2-Back condition
Measurement	Matched stimulus	Non-matched stimulus	Matched stimulus	Non-matched stimulus
After a day shift, P vs C	P: M 449.13, SD 91.29	P: M 393.70, SD 46.44	P: M 450.56, SD 102.8	P: M 357.07, SD 86.31
	C: M 410.41, SD 56.10	C: M 433.16, SD 74.88	C: M 394.20, SD 54.68	C: M 410.75, SD 54.68
	U = 118.0; p = 0.248	U = 89.0; p = 0.035	U = 87.0; p = 0.029	U = 79.0; p = 0.015
Day off in the morning, F vs C	F: M 411.93, SD 56.28	F: M 385.53, SD 49.31	F: M 410.0, SD 49.85	F: M 383.67, SD 52.64
	C: M 428.59, SD 71.73	C: M 376.09, SD 46.71	C: M 374.90, SD 68.04	C: M 395.19, SD 63.91
	U = 112.0; p = 0.558	U = 117.0; p = 0.692	U = 73.0; p = 0.04	U = 122.0; p = 0.835
Day off in the evening	P: M 417.72, SD 66.52	P: M 396.07, SD 61.38	P: M 421.62, SD 75.37	P: M 391.02, SD 103.4
	F: M 368.40, SD 34.01	F: M 401.07, SD 47.09	F: M 405.33, SD 110.9	F: M 421.13, SD 57.85
	C: M 381.88, SD 47.14	C: M 428.06, SD 61.68	C: M 373.12, SD 53.06	C: M 428.59, SD 78.45
Day off in the evening, P vs C	U = 105.0; p = 0.113	U = 116.0; p = 0.222	U = 90.0; p = 0.038	U = 106.0; p = 0.121
Day off in the evening, F vs C	U = 103.5; p = 0.365	U = 102.0; p = 0.335	U = 109.5; p = 0.496	U = 120.0; p = 0.777
Day off in the evening, P vs F	U = 70.0; p = 0.019	U = 126.5,0; p = 0.759	U = 101.0; p = 0.219	U = 90.5; p = 0.108

Note: Comparison of measurements between two groups with the Mann–Whitney U test. C = control group; F = firefighters; P = paramedics.

Table 2. Reaction time and answer correctness for all conditions of the ANT.

Behavioural measure	No cue condition	Central cue condition	Spatial cue condition	Congruent condition	Incongruent condition
Day off in the evening
Reaction time	P: M 561.17, SD 74.09	P: M 550.05, SD 68.58 F:	P: M 520.60, SD 82.65	P: M 496.16, SD 69.28	P: M 591.72, SD 82.04
	F: M 566.29, SD 74.71	M 550.10, SD 76.49 C:	F: M 523.12, SD 80.08	F: M 504.74, SD 78.05	F: M 588.27, SD 78.28
	C: M 524.50, SD 85.31	M 515.13, SD 86.83	C: M 483.96, SD 78.32	C: M 467.35, SD 80.55	C: M 548.37, SD 86.73
Answer correctness	P: M 0.95, SD 0.08	P: M 0.95, SD 0.06	P: M 0.95, SD 0.07	P: M 0.97, SD 0.07	P: M 0.93, SD 0.07
	F: M 0.93, SD 0.13	F: M 0.94, SD 0.10	F: M 0.94, SD 0.12	F: M 0.95, SD 0.09	F: M 0.92, SD 0.14
	C: M 0.97, SD 0.06	C: M 0.97, SD 0.04	C: M 0.97, SD 0.05	C: M 0.99, SD 0.03	C: M 0.95, SD 0.07
Day off in the morning
Reaction time	F: M 561.16, SD 64.05	F: M 558.82, SD 74.61	F: M 522.28, SD 75.13	F: M 508.72, SD 73.58	F: M 586.12, SD 70.35
	C: M 515.66, SD 50.47	C: M 507.00, SD 58.45	C: M 473.14, SD 60.74	C: M 458.83, SD 51.39	C: M 538.37, SD 61.64
Answer correctness	F: M 0.94, SD 0.14	F: M 0.94, SD 0.12	F: M 0.94, SD 0.12	F: M 0.96, SD 0.11	F: M 0.93, SD 0.15
	C: M 0.99, SD 0.02	C: M 0.98, SD 0.02	C: M 0.99, SD 0.01	C: M 1.00, SD 0.01	C: M 0.97, SD 0.003

Note: Measurements on the day off in the morning and evening. ANT = attention network test; C = control group; F = firefighters; P = paramedics.

Figure 3. Evoked potentials in the attention network test to proper stimuli presented in all conditions during recording on the day off in the evening. Note: The full colour version of this figure is available online. CNV = contingent negative variation. Red, paramedics; green, firefighters; blue, control group.

Table 3. P200 potential in the ANT on the frontal and occipital electrodes.

Condition	Electrode	χ^2, Kruskal–Wallis test	p	p (P vs C)	p (P vs F)
No cue	Frontal Occipital	9.58	0.008	0.082	0.009
		11.81	0.003	0.070	0.002
Central cue	Frontal Occipital	13.78	0.001	0.030	0.001
		10.01	0.007	0.084	0.007
Spatial cue	Frontal Occipital	6.86	0.032	0.188	0.036
		6.08	0.048	0.420	0.044
Congruent	Frontal Occipital	12.00	0.002	0.107	0.002
		12.34	0.002	0.101	0.002
Incongruent	Frontal Occipital	11.21	0.004	0.064	0.004
		9.96	0.007	0.092	0.007

Note: Kruskal–Wallis test with Dunn’s post-hoc test. ANT = attention network test; C = control group; F = firefighters; P = paramedics.

Figure 4. Relative value of power (mean and standard deviation) on the occipital electrode in the θ band in the time window of ca. 100–500 ms after presentation of the proper stimulus in the spatial cue condition in the attention network test in the group of paramedics.