Insomnia among female flight attendants: Related factors and its association with mental health

Abstract

BACKGROUND:

Sleep and mental health are very important in the aviation industry. Reports show that gender is one of the risk factors of insomnia, and most Asian flight attendants are female. Therefore, it is necessary to understand insomnia, and the correction to mental health among female flight attendants.

OBJECTIVE:

To investigate the prevalence of insomnia in female flight attendants and its association with mental health.

METHODS:

We used a cross-sectional design. We recruited 412 female flight attendants with more than 3 months of working experience. We collected the socio-demographic and work-related data, measured insomnia and mental health by the Athens Insomnia and Brief Symptom Rating Scales. Descriptive statistics, single-factor analysis of variance, Pearson’s correlation analysis, and structural equation modeling were performed to analyze the relationships.

RESULTS:

There are 45.4% of female flight attendants having insomnia, and 24.8% had suspicious insomnia. The most considerable and serious insomnia problem was falling asleep (15.3%, 4.9%). Factors related to insomnia include smoking, drinking, family load (e.g., housekeeping and caring for family), economic stress and late-night/early morning workdays during last month. Also, insomnia had a direct association with mental health (T = 17.11, p < 0.001).

CONCLUSION:

We found that insomnia is negatively correlated with the above factors and mental health. We recommend that airline industries can run their sleep-education programs and provide relevant mental-health-promotion programs for flight attendants.

Keywords

Sleep work mental hygiene health promotion

1 Introduction

Insomnia is one of the most common sleep disorders worldwide. Physical and mental illness, sleep disorders, medications, environmental factors, and poor sleep habits can contribute to insomnia [1]. A review study indicated that 9.6–19.4% of adults have insomnia from 2000–2017 in Netherlands, United Kingdom, and United States (USA) [2, 3]. In 2020, 14.5% of adults had difficulty in falling asleep in the USA [4].

Insomnia has wide-ranging effects on life, as it causes poor physical and mental health. Studies found that insomnia predicted depression, anxiety, substance abuse or dependence, and suicide [5, 6]. Seriously, it may increase unplanned suicidal behavior because sleep loss can lead to higher levels of impulsivity [7, 8]. In addition, insomnia impacts health reduces job function and increases the risk of workplace accidents and/or errors, which cost significantly more than other accidents or errors [9, 10]. It is noted that accidents or errors are not allowed to happen during flights in the aviation industry. Moreover, it is well known that jet lag affects sleeping quality when flying across time zones, such as nighttime insomnia, and daytime sleepiness [11, 12]. Therefore, the issue of insomnia needs attention in airlines.

A United States National Health Interview Survey in 2017–2018 found that 32.6% of workers report sleeping < 6 hours per night, up from 28.4% in 2008–2009 [13]. Then another review showed the prevalence of insomnia is 12.8–76.4% among shift workers, who were health care workers, home caregivers, industrial workers, and other diverse workers in South Korea, the United States, Iran, Norway, and Japan [14]. However, not only is the risk for insomnia higher among shift workers, but also women have a 40% higher risk than men [15]. A recent survey pointed that 57.7% of flight attendants were screened positive for insomnia. The insomnia rate is obviously higher than previous reports [16].

Insomnia disorder may affect a large proportion of the population worldwide, but there are several significant gaps in the literature on this topic [17]. The most clearly identified demographic risk factors of insomnia include females and aging; insomnia is more prevalent with both the onset of menses and menopause [6]. In addition, the risk groups of insomnia included flight attendants with shift work, circadian disruption, and restricted sleep [16]. Most flight attendants are female in Asia; indeed, in Taiwan, 92% of all flight attendants are female [18].

Studies investigating sleep issue has focused on airline pilots, mostly in male. And few studies have explored the relationships between insomnia and mental health in females who work in flight operations. According to previous studies, the issues of insomnia and mental health among female flight attendants require in-depth study. Therefore, we explored the prevalence of insomnia in female flight attendants and its association with mental health. Based on the report of Shim et al. (2021), the hypotheses of this research were that insomnia has a significant effect on mental health [19].

2 Methods

This study used a cross-sectional design and convenience sampling to elucidate the factors associated with the impact of insomnia on the mental health of flight attendants.

2.1 Participants

In this study, we recruited participants from a Taiwanese airline with flights to North America, Europe, Oceania, and Asia. The home base was Taiwan. To be eligible, the inclusion criteria were (1) female flight attendants, (2) who had worked as flight attendants for more than 3 months, (3) who can speak and understand Chinese. The exclusion criterion was an unwillingness to join this research or complete the questionnaire.

The sample size was determined using the Krejcie & Morgan (1970) sample calculation formula [20]. Our target population was 2843 people in the airline, 338–341 participants are basic required.

2.2 Procedure

This study was approved by the ethics committee of NTNU (IRB number: 201709HS005). The first author recruited participants with the well-training aviation workers in the airline. All potential participants gave informed consent before the start of the study. After agreeing to participate, they completed an anonymous questionnaire online through a link. For convenience, paper anonymous questionnaires were also provided if it is necessary. To recruit enough participants, the study was conducted between November 2017 and October 2018.

2.3 Measures

There were two parts of measurement in this study. The first part was sociodemographic and work-related data. In the second part, we collected insomnia data (AIS-8), and mental health (-5), and asked questions about suicidal ideation.

2.3.1 Sociodemographic and work-related data

Sociodemographic and work-related data were obtained, including age (years); marital status (married or unmarried); smoking (yes or no); drinking (yes or no); exercise (0 none, 1 once a week, 2 more than twice a week); family load (e.g., housekeeping and caring for family) (0, none; 1, slight; 2, moderate; 3, heavy; and 4, sever); economic stress (0, none; 1, slight; 2, moderate; 3, heavy; and 4, extreme); working hours (flight hours in the last week); working days (flight duty days in the last month); late-night and early-morning flight (10 PM–6 AM) duty days in the last month.

2.3.2 Athens Insomnia Scale (AIS-8)

We used the translated Athens Insomnia Scale (AIS-8) questionnaire to measure insomnia during the past month. The Cronbach’s α internal consistency value of the Chinese version is 0.83. The AIS-8 includes eight items, including “Falling asleep/ Sleep induction”, “Awakenings during the night”, “Waking earlier than desired”, “Total sleep duration”, “Overall sleep quality”, “Sense of well-being during the day”, “Functioning capacity during the day”, and “Sleepiness during the day”. The questionnaire uses a four-point Likert scale, each item ranging from 0 (no problem) to 3 (a very serious problem), with total scores of 0–24. A total score < 5 indicates no problem, a score of 4–5 indicates some suspicion of insomnia, and a score≥6 indicates insomnia [21, 22]. The Cronbach’s α was 0.81.

2.3.3 Brief Symptom Rating Scale (BSRS-5)

Mental health was measured using the Taiwan BSRS-5, a structured questionnaire used to screen psychological disorders in the past week. Cronbach’s α of the Chinese version is 0.84. We used five items, including anxiety (feeling tense or high-strung), hostility (feeling easily annoyed or irritated), depression (feeling depressed or in a low mood), interpersonal sensitivity (feeling inferior to others), and additional symptoms (having trouble falling asleep in the past week). The score for each item ranged from 0 to 4 (0, not at all; 1, slight; 2, moderate; 3, heavy; and 4, extreme). The maximum total score on the BSRS-5 is 14. Scores of 10–14 indicate a moderate mood disorder, scores of 6–9 indicate a mild mood disorder, and scores < 5 indicate normal [23]. The Cronbach’s α was 0.79.

Except these five items of BSRS-5, we also measure the suicidal ideation. Suicidal ideation was measured using a sixth additional item on the Taiwan BSRS-5. Only one direct question was asked about the urge to commit suicide in the past week. Scores ranged from 0 to 4 (0, not at all; 1, slight; 2, moderate; 3, strong; and 4, extreme) [23].

2.4 Statistical analysis

Descriptive analysis, a single-factor analysis of variance, Pearson’s correlation analysis was used to analyze the data and explore the relationships between the insomnia scores and numerous variables. We carried out a structural equation model (SEM) with 1,000 bootstraps to analysis the direct and moderating effects of insomnia on mental health and suicidal ideations. We calculated bias-corrected (BC) 95% confidence intervals (CIs) and p-values. Descriptive and inferential analyses were performed using SPSS Statistics 24 software (IBM Corp., Armonk, NY, USA). The SEM was constructed using Smart PLS 4 (SmartPLS GmbH, Schleswig-Holstein, Germany).

3 Results

3.1 Participant characteristics

The study population comprised 412 female flight attendants; 54.1% were married, 73.8% were in the age range 31–50 years, and 14.1–15% had more than a moderate family workload and economic stress. Most participants reported not smoking (90.0%) or no drinking (98.8%), and more than once exercise a week (58.8%). More than half of the participants had worked days of 6–10 hours in the last week (63.3%) and 16–20 days in the last month (68.2%), and 67.7% had worked fewer than five late-night and early morning (10 PM– 6 AM) flights in the last month (Table 1).

Table 1
Characteristics of the samples by insomnia score (n = 412)

Variables N % AIS-8 scores F p Post hoc

M SD

Age (years) 1.1 0.348

a). 21–30 67 16.3 5.73 3.84

b). 31–40 153 37.1 5.84 3.58

c). 41–50 151 36.7 5.3 3.05

d). >50 41 10 4.93 3.76

Marital status 1.11 0.293

a). Single 189 45.9 5.34 3.39

b). Married 223 54.1 5.7 3.52

Smoking 12.38 .000* b > a

a). No 371 90 5.34 3.36

b). Yes 41 10 7.32 3.9

Drinking 9.36 .002 b > a

a). No 407 98.8 5.48 3.42

b). Yes 5 1.2 10.2 4.32

Exercise 1.15 0.317

a). None 174 42.2 5.73 3.33

b). Once a week 123 29.9 5.64 3.61

c). More than twice a week 115 27.9 5.12 3.48

Family load 7.65 .001 c>a; c > b

a). None 165 40 4.9 3.57

b). Slight 185 44.9 5.66 3.23

c). Heavy or severe 62 15 6.85 3.47

Economic stress 10.5 .000* b > a; c > a

a). None 190 46.1 4.72 3.36

b). Slight 164 39.8 6.12 3.24

c). Moderate, heavy or extreme 58 14.1 6.55 3.84

Working hours/week 2.46 0.087

a). 1–5 111 26.9 5.16 3.34

b). 6–10 261 63.3 5.53 3.45

c). ≥11 40 9.7 6.58 3.74

Working days/month 2.09 0.1

a). ≤10 days 20 4.9 4.95 2.56

b). 11–15 days 87 21.1 5.32 3.46

c). 16–20 days 281 68.2 5.5 3.44

d). ≥21 days 24 5.8 7.17 4.07

Late night/early-morning working days/month 3.13 .045*

a). 0–4 days 279 67.7 5.25 3.34

b). 5–9 days 114 27.7 6.07 3.53

c). ≥10 days 19 4.6 6.53 4.27

Variables	N	%	AIS-8 scores	F	p	Post hoc
Age (years)					1.1	0.348
a). 21–30	67	16.3	5.73	3.84
b). 31–40	153	37.1	5.84	3.58
c). 41–50	151	36.7	5.3	3.05
d). >50	41	10	4.93	3.76
Marital status					1.11	0.293
a). Single	189	45.9	5.34	3.39
b). Married	223	54.1	5.7	3.52
Smoking					12.38	.000***	b > a
a). No	371	90	5.34	3.36
b). Yes	41	10	7.32	3.9
Drinking					9.36	.002**	b > a
a). No	407	98.8	5.48	3.42
b). Yes	5	1.2	10.2	4.32
Exercise					1.15	0.317
a). None	174	42.2	5.73	3.33
b). Once a week	123	29.9	5.64	3.61
c). More than twice a week	115	27.9	5.12	3.48
Family load					7.65	.001**	c>a; c > b
a). None	165	40	4.9	3.57
b). Slight	185	44.9	5.66	3.23
c). Heavy or severe	62	15	6.85	3.47
Economic stress					10.5	.000***	b > a; c > a
a). None	190	46.1	4.72	3.36
b). Slight	164	39.8	6.12	3.24
c). Moderate, heavy or extreme	58	14.1	6.55	3.84
Working hours/week					2.46	0.087
a). 1–5	111	26.9	5.16	3.34
b). 6–10	261	63.3	5.53	3.45
c). ≥11	40	9.7	6.58	3.74
Working days/month					2.09	0.1
a). ≤10 days	20	4.9	4.95	2.56
b). 11–15 days	87	21.1	5.32	3.46
c). 16–20 days	281	68.2	5.5	3.44
d). ≥21 days	24	5.8	7.17	4.07
Late night/early-morning working days/month					3.13	.045*
a). 0–4 days	279	67.7	5.25	3.34
b). 5–9 days	114	27.7	6.07	3.53
c). ≥10 days	19	4.6	6.53	4.27

*p < 0.05; **p < 0.01; ***p < 0.001.

3.2 Distributions of insomnia and sleep hours

About 45.4% of the participants suffered from insomnia, 24.8% were suspected of suffering from insomnia, and 29.9% had no insomnia. The most considerable and serious insomnia problems were falling asleep (15.3%, 4.9%), awakenings during the night (10.7%, 1.0%), waking earlier than desired (10.0%, 0.7%), and total sleep duration (9.5%, 1.7%). Nearly half of the participants reported minor insomnia problems, such as falling asleep (47.8%), awaking during the night (56.3% minor), waking earlier than desired (51.0%), total sleep duration (57.8%), and overall sleep quality (57.8%). Except for sleepiness during the day (40.3% no problem), there was a total of 63.8–69.9% reported no problems with daytime function (sense of well-being during the day and functioning during the day). The percentage of insufficient sleep hours among the participants included: on workdays, 33% of the participants slept less than 7 hours/day (56.3% 7–8 hours; 10.7% >8 hours), but only 31.1% of the participants thought their total sleep was sufficient (no problems). More than 80% of the participants slept more than 7 hours on non-workdays (47.6% 7–8 hours; 35.7% >8 hours) (Table 2).

Table 2
Distributions of insomnia and sleep hours characters (n = 412)

Variable No problem n (%) Minor problem n (%) Considerable problem n (%) Serious problem n (%)

AIS-8 scales

1. Falling asleep/ Sleep induction 132 (32.0) 197 (47.8) 63 (15.3) 20 (4.9)

2. Awakenings during the night 132 (32.0) 232 (56.3) 44 (10.7) 4 (1.0)

3. Waking earlier than desired 158 (38.3) 210 (51.0) 41 (10.0) 3 (0.7)

4. Total sleep duration 128 (31.1) 238 (57.8) 39 (9.5) 7 (1.7)

5. Overall sleep quality 133 (32.3) 238 (57.8) 33 (8.0) 8 (1.9)

6. Sense of well-being during the day 288 (69.9) 107 (26.0) 15 (3.6) 2 (0.5)

7. Functioning capacity during the day 263 (63.8) 131 (31.8) 14 (3.4) 4 (1.0)

8. Sleepiness during the day 166 (40.3) 213 (51.7) 27 (6.6) 6 (1.5)

Sleep hours <7 hours 7–8 hours >8 hours

■ Sleep hours during the workday 136 (33.0%) 232 (56.3%) 44(10.7)

■ Sleep hours during non-workday 69 (16.7%) 196 (47.6%) 147 (35.7%)

Insomnia No problem Suspicion of insomnia Insomnia

123 (29.9%) 102(24.8%) 187(45.4%)

AIS-8 scores Mean=5.53 SD=3.46

Variable	No problem n (%)	Minor problem n (%)	Considerable problem n (%)	Serious problem n (%)
AIS-8 scales
1. Falling asleep/ Sleep induction	132 (32.0)	197 (47.8)	63 (15.3)	20 (4.9)
2. Awakenings during the night	132 (32.0)	232 (56.3)	44 (10.7)	4 (1.0)
3. Waking earlier than desired	158 (38.3)	210 (51.0)	41 (10.0)	3 (0.7)
4. Total sleep duration	128 (31.1)	238 (57.8)	39 (9.5)	7 (1.7)
5. Overall sleep quality	133 (32.3)	238 (57.8)	33 (8.0)	8 (1.9)
6. Sense of well-being during the day	288 (69.9)	107 (26.0)	15 (3.6)	2 (0.5)
7. Functioning capacity during the day	263 (63.8)	131 (31.8)	14 (3.4)	4 (1.0)
8. Sleepiness during the day	166 (40.3)	213 (51.7)	27 (6.6)	6 (1.5)

AIS-8 scales: Athens insomnia scale.

3.3 Insomnia differences in variables according to participant characteristics

The insomnia scores of the flight attendants differed significantly in terms of smoking (F = 12.38, p = 0.000), drinking (F = 9.36, p = 0.002), family load (F = 7.65, p = 0.001), economic stress (F = 10.50, p = 0.000), and late night/early-morning workdays (F = 3.13, p = 0.45). Higher insomnia scores were observed for the drinking group (M = 10.20, SD = 4.32), smoking group (M = 7.32, SD = 3.90), and the group of working days/month≥21 days (M = 7.17, SD = 4.07). But there was no differences were detected for working hours or days (F = 2.46, p = 0.087; F = 2.09, p = 0.100) (Table 1).

3.4 Distributions and the correction between insomnia, mental health, and suicidal ideation

The mean insomnia (AIS-8) score was 5.53 (SD = 3.46), the mean health status (BSRS-5) score was 3.67 (SD = 2.82). The average of mental health was normal (healthy) among the participants (n = 322, 78.2%), only twenty-one (5.1%) participants had slight suicidal ideation, and one (0.2%) had moderate suicidal ideation. The mental health (r = .17, p < .001) was significantly correlated with insomnia (Table 3).

Table 3
The descriptive data and Pearson’s correlations between the variables (n = 412)

Items Mean SD n % Insomnia

r p

■ Mental health (BSRS-5) 3.67 2.82 0.17 .000***

1. Normal 2.54 1.7 322 78.2

2. Mild mood disorder 6.88 0.98 73 17.7

3. Moderate mood disorder 11.47 2.06 17 4.1

■ Suicidal ideation

1. Not at all 390 94.7

2. Slight 21 5.1

3. Moderate 1 0.2

4. Strong or extreme 0 0

Items	Mean	SD	n	%	Insomnia
■ Mental health (BSRS-5)	3.67	2.82			0.17	.000***
1. Normal	2.54	1.7	322	78.2
2. Mild mood disorder	6.88	0.98	73	17.7
3. Moderate mood disorder	11.47	2.06	17	4.1
■ Suicidal ideation
1. Not at all			390	94.7
2. Slight			21	5.1
3. Moderate			1	0.2
4. Strong or extreme			0	0

***p < 0.001. Insomnia: Total scores of AIS-8; Mental health: Total scores of BSRS-5.

3.5 SEM analysis

In Table 3, the insomnia had a significant direct effect on mental health (T = 17.11, p < 0.000, BC 95% CI:0.49, 0.61); the mental health had a significant direct effect on suicidal ideations (T = 6.03, p < 0.000, BC 95% CI:0.23, 0.44); but insomnia had no direct effect on suicidal ideations (T = 0.59, p = 0.552, BC 95% CI: – 0.11, 0.05). As we see in Fig. 1, the moderated mediation analysis results show that insomnia had a significant moderating effect on the association between mental health and suicidal ideation (T = 2.63, p = 0.009, BC 95% CI: 0.04, 0.28, path coefficients = 0.162) (Table 4, Fig. 1).

Fig. 1

The moderated model for the relationship between insomnia, mental health, and suicidal ideation (path coefficients and p-values).

Table 4

Direct effect and total indirect effects between insomnia, mental health, and suicidal ideation (n = 412)

Effect	Original sample (O)	Sample mean (M)	STDEV	T	Bootstrapped 1,000 times Bias-Corrected 95% CI		P
					Lower	Upper
Direct effects
Insomnia ⟶ Mental health	0.55	0.55	0.03	17.11	0.49	0.61	0.000***
Mental health⟶ Suicidal ideations	0.34	0.34	0.05	6.03	0.23	0.44	0.000***
Insomnia ⟶ Suicidal ideations	– 0.02	– 0.02	0.04	0.59	– 0.11	0.05	0.552
Total effects
Insomnia × Mental health ⟶ Suicidal ideations	0.16	0.16	0.06	2.63	0.04	0.28	0.009**

**p < 0.01; ***p < 0.001.

4 Discussion

According to the results, 45.4% of the participants suffer from insomnia. Serious sleep problems included falling asleep, awaking during the night, waking earlier than desired, and total sleep duration. Participants with a higher family load or economic stress had higher insomnia scores, which were the same as those with a smoking or alcohol drinking habit, or the group who worked more than 5 days of late-night/early morning duties. Mental health exhibited a significant relationship with insomnia. The findings reveal a moderate link between insomnia and suicidal ideation when taking mental health into account.

About 20–30% of adults worldwide have a sleep disorder, and 32.6% of working adults report sleeping≤6 hours per night [13, 24]. In Taiwan, 23.3% of shift workers have chronic insomnia [25]. We found a similar percentage of insufficient sleep during workday (33% <7hours), but a much higher prevalence of insomnia (45.4%). This finding agrees with previous studies showing that sex (female), night work, and jet lag are related to insomnia [9, 11]. Flight attendants usually have irregular-shift work schedules, frequently cross time zones, and have long-haul flights that may affect their sleep. Furthermore, the high percentage of insomnia (45.4%) in this study may be related to the gender difference by all the participants being women, such as physical effects, the family, or job load. Baker et al. reported that premenstrual syndrome produces insomnia-like symptoms before and during a period [26]. Other studies have found that female workers with high work-family conflicts or stress have a higher risk for insomnia [27, 28]. The participants with a relatively high family load or economic stress had higher insomnia scores. Nevertheless, it needed to be depth studied and compared with male flight attendants in future studies.

Significant differences in smoking and drinking habits were observed among the flight attendants, similar to others’ findings [29, 30]. However, unlike those previous investigations, no significant differences in insomnia scores were observed according to marital status in our study. Researchers found that married participants had a lower percentage of insomnia, due to economic and social/emotional support from the relationship [31, 32]. We speculate that in this study the lack of a difference in insomnia scores between the single and married groups may have reflected that the flight attendants did not need financial support from a partner due to the good welfare benefits and high salaries of flight attendants in Taiwan [33]. Also, no association of age difference with insomnia was observed in this study or in Lin et al. [29], which disagrees with some previous findings [9, 32]. The lack of an association of age might be attributable to some flight attendants preferring to switch shift work to day work when they had poor health or sleep conditions [34].

This study was relevant to previous surveys that suggested that insomnia can cause poor mental health and suicidal ideation [27, 35]. A study found a 3.533-fold suicide risk in patients with insomnia compared to patients without insomnia [36]. Poor mental health also has a complex bidirectional relationship with depression, anxiety disorders, and substance use [37]. Therefore, once flight attendants have insomnia. They may need help and provide recommendations from health professional managers to prevent severe health problems. Jet lag is the main reason which causes insomnia among flight attendants.

Besides the effects of jet lag, intake of caffeine and the use of cigarettes and alcohol are predictors of insomnia and sleep quality [38]. Therefore, personal habits and sleep hygiene are important in preventing insomnia. We suggest that companies should provide sleep-education programs and reduce the number of late-night/early morning flights across more than five time zones among attendants at risk for insomnia. We recommend that such attendants be given cognitive-behavioral therapy [39]. If such therapy for insomnia is not sufficiently effective or is not available, music therapy, exercise, or acupuncture may be used as adjuvant therapy [39–41]. Previous studies were suggested to address the studies focused on investigating mediators of insomnia and suicide relationship in the aviation industry; objective longitudinal studies are needed. This study is one of the first to investigate the factors related to insomnia, and model insomnia, mental health, and suicidal ideation in female flight attendants.

4.1 Limitations

Several limitations of this study should be discussed. This was a cross-sectional survey which only can verify an association between the variable and cannot be verified the impact of insomnia, and data were collected from an international airline using convenience sampling. The findings may not reflect the situations of flight attendants working for other airlines. In addition, the instruments used are not diagnostic tools, e.g. questions about family load and economic stress that does not accurately quantify. Furthermore, self-report instruments are potentially subject to biases, and therefore cannot substitute for a comprehensive evaluation, e.g. the different periods that we evaluated (Athens Insomnia Scale: one month; Brief Symptom Rating Scale: one week,); investigate through objective longitudinal studies are needed be more reliable and accurately investigating the relationship between insomnia and mental health. We may suggest further studies can use the same method to explore other airlines.

5 Conclusion

We found that insomnia was associated with mental health among female flight attendants. This study revealed that insomnia affected the mental health of female flight attendants and may cause suicidal ideation. The related factors were family load, economic stress, late-night/early morning workdays, and cigarette and alcohol use. Therefore, there is a need to investigate further the insomnia group and those with poor mental health and to encourage them to seek early and appropriate treatment. Airline companies should create an environment that encourages flight attendants to do a insomnia test screening, and seek help, and promote a work culture that protects the health of employees and promotes flight safety.

Footnotes

Ethical approval

This study was approved by the ethics committee of NTNU (IRB number: 201709HS005).

Informed consent

All potential participants gave informed consent before the start of the study.

Acknowledgments

The authors would like to thank all participating flight attendants and unit coordinators.

Conflict of interest

There is no conflict of interest to declare.

Funding

This research did not receive any specific grants from funding agencies in the public, commercial, or not-for-profit sectors.

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Sleep hours	<7 hours	7–8 hours	>8 hours
■ Sleep hours during the workday	136 (33.0%)	232 (56.3%)	44(10.7)
■ Sleep hours during non-workday	69 (16.7%)	196 (47.6%)	147 (35.7%)
Insomnia	No problem	Suspicion of insomnia	Insomnia
	123 (29.9%)	102(24.8%)	187(45.4%)
AIS-8 scores	Mean=5.53	SD=3.46