Examining courses of sleep quality and sleepiness in full 2 weeks on/2 weeks off offshore day shift rotations

Figures & data

Figure 1. Flowchart.

Table 1. Sample characteristics of the final study sample.

	N	Mean	SD	Range
Age (years)	42	42	12.1	[21–63]
BMI	41	26.5	3.4	[21–36]
Job tenure (years)	41	6.6	6.2	[1–27]
Sleep quality past month (PSQI)	38	6.4	1.6	[4–12]
Mean mid sleep corrected (hh:mm)	38	03:01	00:37	[02:00–04:17]
	N	%
Job demands
Mentally demanding	14	34
Physically demanding	5	12
Both mentally and physically demanding	22	54

Participants were excluded from the measure if missing values were found.

PSQI: Pittsburgh Sleep Quality Index; BMI: body mass index.

Table 2. Mean scores of the investigated sleep quality and sleepiness parameters for the pre-offshore (1 week), offshore (2weeks) and post-offshore (1 week) work periods.

	Pre-offshore			Offshore			Post-offshore
	Mean	SD	Range	Mean	SD	Range	Mean	SD	Range
Actigraphy
TIB (min)	495.4	77.5	293–759	453.6	63.3	250–869	502.3	105.3	51–977
TST (min)	420.1	67.5	209–684	389.3	57.9	210–857	427.4	100.8	19–912
SL (min)	10.9	16.1	0–93	11.1	17.3	0–130	9.4	15.3	0–84
SE (%)	85.1	6.9	57.6–99.5	86.1	6.7	59.6–99.8	84.8	7.8	37.3–99.7
CSD
Sleep quality	3.5	0.8	1–5	3.3	0.8	1–5	3.5	0.8	1–5
Level of rest	3.4	0.9	1–5	3.0	0.9	1–5	3.2	0.9	1–5
KSS
Morning	3.7	1.6	1–8	4.0	1.7	1–9	4.0	1.7	1–9
Evening	4.3	1.9	1–9	4.6	1.9	1–9	4.9	2.2	1–9

TIB: time in bed; TST: total sleep time; SL: sleep latency; SE%: sleep efficiency percentage; CSD: consensus sleep diary; KSS: Karolinska Sleepiness Scale.

Table 3. Mean differences and odds ratios of daily Karolinska Sleepiness Scores (KSS), consensus sleep diary (CSD) items and actigraphy recordings between the pre-offshore (1 week), offshore (2 weeks) and post-offshore (1 week) work periods.

	Pre-offshore			Offshore	Post-offshore
	Mean diff	95% CI	p Value		Mean diff	95% CI	p Value
KSS
Morning	−0.25	−0.41 to –0.08	0.004	–	−0.12	−0.31 to 0.06	0.193
Morning & Chronotype	−30	−0.48 to –0.12	0.001	–	−0.07	−0.26 to 0.12	0.479
Evening	−0.22	−0.41 to –0.04	0.020	–	0.16	−0.04 to 0.37	0.121
Evening & BMI	−0.22	−0.41 to –0.03	0.023	–	0.14	−0.06 to 0.35	0.177
Evening & PSQI	−0.17	−0.36 to 0.03	0.092	–	0.11	−0.11 to 0.32	0.326
CSD
Sleep quality	0.18	0.08 to 0.29	0.001	–	0.26	0.14 to 0.38	<0.001
Level of Rest	0.34	0.23 to 0.45	<0.001	–	0.26	0.14 to 0.38	<0.001
Actigraphy
TIB	42.13	31.49 to 52.76	<0.001	–	50.11	38.51 to 61.71	<0.001
TST	29.12	19.25 to 39.10	<0.001	–	40.25	29.43 to 51.07	<0.001
	OR	95% CI	p Value		OR	95% CI	p Value
SL	0.92	0.67 to 1.27	0.617	–	1.19	0.85 to 1.69	0.313
SE%	1.81	1.26 to 2.61	0.001	–	1.60	1.08 to 2.38	0.021

Offshore work period serves as reference category.

PSQI: Pittsburgh Sleep Quality Index; TIB: time in bed; TST: total sleep time; SL: sleep latency; SE%: sleep efficiency percentage.

Potential explanatory variables were added to the model if the regression coefficient of the baseline model decreased the regression coefficients of the adjusted model by at least 10%. This was the case for morning KSS (chronotype) as well as evening KSS (BMI and PSQI).

Figure 2. Courses of objective TIB, TST, SE% and SL actigraphy recordings across full 2 weeks on/2 weeks off offshore shift rotations.

Figure 3. Courses of self-reported sleep quality, level of rest and sleepiness across 2 weeks on/2 weeks off offshore shift rotations.