Shift work and sleep disorder comorbidity tend to go hand in hand

Figures & data

Table 1. Socio-demographic characteristics (mean, SD: standard deviation) of day workers and shift workers, within the age range of 21–60 years, and drawn from a representative sample of 2089 persons. Data as indicated in first column. Pairwise comparisons were made using Pearson χ², t-test or Mann–Whitney U-statistic.

Socio-demographics	Day workers (n = 971)	Shift workers (n = 250)
Gender (% males)	51.8	52.4
Age (mean years (SD))	41.0 (10.4)	39.4 (11.9)
Partner (% partnered)^1	79.2	69.3**
Child(-ren) at home (%)^2	59.2	59.8
Education (mean rating 1–8)^3	5.2 (2.1)	4.4 (1.9)***
Income (mean rating 1–7)^4	4.2 (1.6)	3.9 (1.5)
Housekeeping (mean rating 1–3)^5	2.0 (1.0)	2.1 (1.1)

1. Percentage of individuals with a regular partner

2. Percentage of individuals with 1 or more children living at home

3. Score 1 for no formal education, score 8 for Master degree

4. Score 1 for well below average, score 4 for average, score 7 for well above average

5. Score 1 for ‘myself’, score 2 for ‘both of us equally’, score 3 for ‘my partner’.

** p < 0.01; *** p < 0.001

Table 2. Mean (SD) scores for 12 sleep-related variables (range of variation), classified into 4 clusters.

Sleep-related variables	Day work (N = 971)	Shift work (N = 250)
Sleep Duration**
Sleep duration (4–9h)	6.92 (1.02)	6.89 (1.12)
Sleep need (4–9h)	7.50 (0.89)	7.42 (1.07)
Napping frequency (0–4 x/wk)	0.55 (0.97)	0.83 (1.09)**
Sleep Timing***
Morningness – Eveningness (1–9)	5.01 (2.34)	5.55 (2.29)**
Poor sleep & Inability to sleep at usual times (1–5)	1.59 (0.93)	1.95 (1.12)***
Sleep onset variability (1–5)	1.87 (1.0)	2.61 (1.28)***
Sleep Quality*
Good – poor sleeper (1–5)	2.49 (0.90)	2.64 (0.96)*
Poor sleep quality & not well-rested (1–5)	2.12 (1.14)	2.33 (1.20)**
Worry about health consequences poor sleep (1–5)	1.76 (1.01)	1.96 (1.08)**
Daytime Functioning
Fatigue (1–5)	2.73 (0.97)	2.85 (0.98)
Sleepiness, bad mood, lack of energy, etc. (1–5)	2.55 (1.19)	2.65 (1.22)
Malfunctioning due to insufficient sleep (1–5)	1.90 (0.99)	1.98 (1.03)

*p < 0.05

**p < 0.01

***p < 0.001.

Table 3. Prevalence rates (95% Confidence interval). Asterisk (column 3) indicates a significant outcome of a Pearson χ²-test for shift workers versus day workers, respectively, for age (column 4; p < .05). Column 4: D = Day work, S = Shift work.

Sleep Disorders	Day Workers	Shift Workers	Age categories 21–30 → 51–60
General Sleep Disturbance	24.6 (22.0–27.4)	39.0* (33.2–45.2)	D*: 28.8 – 17.4 – 30.6 – 21.0 S*: 52.2 – 45.2 – 26.5 – 30.2
Insomnia	4.9 (3.8–6.5)	8.8* (5.9–13.0)	D*: 6.3 – 0.8 – 7.5 – 5.6 S*: 11.9 – 8.1 – 7.4 – 7.5
Circadian Rhythm Sleep Disorder	2.8 (1.9–4.1)	9.2* (6.2–13.4)	D*: 2.1 – 0.8 – 4.9 – 2.8 S: 9.0 – 11.3 – 10.3 – 5.6
Parasomnia	3.8 (2.8–5.2)	10.8* (7.5–15.4)	D: 5.2 – 5.4 – 2.9 – 2.3 S*: 20.9 – 13.1 – 2.9 – 3.7
Hypersomnolence	3.7 (2.7–5.1)	8.8* (5.9–12.9)	D: 6.3 – 2.7 – 2.9 – 3.3 S*: 17.9 – 6.5 – 4.4. – 5.6
Leg movements	9.6 (7.9 – 11.6)	16.8* (12.7 – 21.9)	D: 12.5 – 7.7 – 9.4 – 8.9 S*: 32.8 – 12.9 – 10.3 – 11.1
Sleep-related Breathing Disorder	6.1 (4.7 – 7.8)	6.8 (4.3 – 10.9)	D: 7.8 – 5.0 – 7.2 – 4.7 S: 9.0 – 9.7 – 4.4 – 5.6
Comorbidity	8.1 (6.6 – 10.0)	18.8* (14.4 – 24.1)	D: 8.9 – 5.4 – 10.1 – 7.9
			S*: 31.3 – 14.5 – 17.6 – 9.4

Figure 1. Prevalence rates of a general sleep disturbance among day workers and shift workers versus age. Error bars: 95% confidence intervals. Numbers of day workers versus shift workers for the four age groups were respectively: 191 versus 67, 259 versus 61, 307 versus 68, 214 versus 53.

Figure 2. Prevalence rates of a general sleep disturbance among single and partnered day workers and shift workers. Error bars represent 95% confidence intervals. Numbers of single versus partnered workers among the day workers and shift workers were, respectively, 202 versus 770 and 77 versus 173.