An exploratory study examining the associations between sunlight exposure, sleep behaviours and sleep outcomes during an Arctic summer

Figures & data

Table 1. Demographic, lifestyle and sleep characteristics of the study sample (n=19)

Variable	Category	% (n)
Demographic
Arctic Residency	Year-round Arctic Resident	47% (10)
	Seasonal Employee	53% (9)
Gender	Male	42% (8)
	Female	58% (11)
Race/Ethnicity	White	84% (16)
	Other^a	16% (3)
Education Level	High School Diploma or GED	16% (3)
	Associate’s or Technical Degree	11% (2)
	Bachelor’s Degree	63% (12)
	Advanced Degree	11% (2)
Age (years)	18–24	16% (3)
	25–34	42% (8)
	35–59	26% (5)
	60 and older	16% (3)
Lifestyle
Caffeinated Beverage Intake (daily)	0	26% (5)
	1 to 2 drinks	32% (6)
	3 to 4 drinks	26% (5)
	5 or more drinks	16% (3)
Alcohol Intake (weekly)	Never	32% (6)
	Every other week	11% (2)
	1 to 2 days per week	42% (8)
	3 to 4 days per week	11% (2)
	More than 5 days per week	5% (1)
Tobacco Use (regular use in past month)	Yes	5% (1)
	No	95% (18)
Exercise Habits (daily)	Never	26% (5)
	1 to 2 days per week	32% (6)
	3 to 4 days per week	26% (5)
	More than 5 days per week	16% (3)
Shift Work (current)	Yes	63% (12)
	No	46% (7)
Sleep Characteristics
History of a Sleep Disorder	Yes	16% (3)
	No	84% (16)
Chronotype	Morning	11% (2)
	Intermediate	74% (14)
	Evening	16% (3)
Use of Sleep Medication	Yes	47% (9)
	No	53% (10)
Use of Alerting Medication	Yes	5% (1)
	No	95% (18)

^a The race/ethnicity category “other” consisted of individuals who identified as multi-racial (n=2) or did not identify their race/ethnicity on the survey (n=1).

Table 2. Mean and median self-reported sleep outcomes^a in Alaskan workers living in and/or near the Arctic Circle (n=19)

Sleep Outcomes	Mean ± SD	Median (Ranges)
Sleep Quality (PSQI score)	7.16 ± 3.82	6.0 (2.0–16.0)
Sleep Onset Latency (minutes)	29.32 ± 23.51	28.0 (1.0–90.0)
Sleep Duration (hours)	7.10 ± 1.51	7.0 (5.0–11.0)
Sleep Efficiency (%)	85% ± 14.86	89.5% (53–100%)
Insomnia Severity Index score	6.79 ± 3.90	7.0 (1.0–13.0)
Daytime Sleepiness (1–10 scale)	3.45 ± 1.46	3.0 (1.0–7.0)
Insufficient Sleep (days in past month)	8.39 ± 7.85	5.0 (2.0–31.0)

Abbreviations: PSQI, Pittsburgh Sleep Quality Index.

^a Sleep outcomes were assessed via survey questions that asked participants to answer questions based on their typical sleep and sleep schedules over the past month.

Table 3. Pearson correlation coefficients [95% confidence intervals] between Sleep Hygiene Index scores and sleep outcomes^a in Alaskan workers living in and/or near the Arctic Circle (n=19)

	Sleep Quality (PSQI Score)	SOL	Sleep Duration	SE^b	ISI	Daytime Sleepiness	Insuff. Sleep
SHI	−.02 [−.47, .44]	−.10 [−.53, .37]	.12 [−.35, .54]	.18 [−.31, .60]	.25 [−.23, .63]	.62* [.23, .84]	.13 [−.34, .55]

Abbreviations: PSQI, Pittsburgh Sleep Quality Index; SOL, sleep onset latency; SE, sleep efficiency; ISI, Insomnia Severity Index; Insuff. Sleep, insufficient sleep; SHI, Sleep Hygiene Index.

^a Sleep outcomes were assessed via survey questions that asked participants to answer questions based on their typical sleep and sleep schedules over the past month.

^b n=18.

* Significant at the p≤.01 level.

Table 4. Pearson correlation coefficients [95% confidence intervals] for daily sunlight exposures and sleep outcomes^a in Alaskan workers living in and/or near the Arctic circle (n=18)

	Day Sun (work)	Day Sun (off)	PM Sun (work)	PM Sun (off)
Sleep Quality	.39	.35	.07	.03
(PSQI Score)	[-.09, .72]	[-.14, .70]	[-.41, .52]	[-.44, .49]
Sleep Onset Latency	.33	.24	.26	.18
	[-.16, .69]	[-.26, .64]	[-.24, .65]	[-.31, .60]
Sleep Duration	-.32	-.35	.14	.14
	[-.68, .17]	[-.70, .14]	[-.35, .57]	[-35, .57]
Sleep Efficiency	-.14	-.04	.26	.28
	[-.58, .37]	[-.51, .45]	[-.25, .66]	[-.23, .67]
Insomnia Severity Index	.21	.21	.00	-.06
	[-.28, .62]	[-.28, .62]	[-.47, .47]	[-.51, .42]
Daytime Sleepiness	-.10	-.20	-.10	-.09
	[-.54, .38]	[-.61, .29]	[-.54, .38]	[-.53, .39]
Insufficient Sleep	.34	.30	.19	.15
	[-.15, .70]	[-.19, .67]	[-.30, .60]	[-.34, .58]

Table 5. Mean and median values of sleep outcomes^a by weekly daytime and evening sunlight exposure duration (long versus short) in Alaskan workers living in and/or near the Arctic circle (n=18)

	Weekly daytime sunlight exposure ^b					Weekly evening sunlight exposure ^c
	Long (>45 hrs) n=8		Short (<45 hrs) n=10			Long (>16 hrs) n=7		Short (<16 hrs) n=11
Outcomes	Mean (SD)	Median (range)	Mean (SD)	Median (range)	Z (p)	Mean (SD)	Median (range)	Mean (SD)	Median (range)	Z (p)
Sleep Quality (PSQI Score)	8.6 (4.5)	7.0 (3.0–16.0)	5.9 (3.1)	5.0 (2.0–11.0)	−1.57 (0.12)	6.7 (3.2)	6.0 (3.0–13.0)	7.4 (4.5)	5.0 (2.0–16.0)	−0.14 (0.89)
Sleep Onset Latency (min)	35.1 (30.4)	35.0 (1.0–90.0)	24.6 (18.2)	20.0 (5.0–60.0)	−0.58 (0.56)	31.4 (29.0)	20.0 (5.0–90.0)	27.9 (22.1)	28.0 (1.0–60.0)	−0.23 (0.82)
Sleep Duration (hr)	6.4 (0.9)	6.3 (5.0–8.0)	7.8 (1.7)	8.0 (5.0–11.0)	−1.98 (0.05)	7.4 (1.8)	7.0 (6.0–11.0)	7.1 (1.4)	7.0 (5.0–8.5)	−0.05 (0.96)
Sleep Efficiency^b (%)	83.4 (17.6)	86.5 (53–100)	88 (14.6)	90 (54–100)	−0.44 (0.26)	91 (11.7)	94 (70–100)	82.3 (17.8)	87 (53–100)	−0.95 (0.34)
Insomnia Severity Index	7.8 (3.4)	7.0 (4.0–13.0)	5.8 (4.4)	5.0 (1.0–12.0)	−1.12 (0.26)	6.0 (4.0)	6.0 (1.0–12.0)	7.1 (4.1)	7.0 (1.0–13.0)	−0.55 (0.59)
Daytime Sleepiness	3.2 (1.4)	3.0 (1.0–6.0)	3.4 (1.4)	3.0 (2.0–7.0)	−0.15 (0.88)	3.2 (1.3)	3.0 (2.0–6.0)	3.4 (1.4)	3.0 (1.0–7.0)	−0.50 (0.62)
Insufficient Sleep	8.9 (6.2)	7.5 (2.0–20.0)	5.8 (5.3)	4.5 (2.0–20.0)	−1.08 (0.28)	7.6 (4.7)	8.0 (2.0–14.0)	6.8 (6.6)	4.0 (2.0–20.0)	−0.73 (0.46)

Abbreviations: PSQI, Pittsburgh Sleep Quality Index; Hrs, hours; Sleepiness, self-reported sleepiness (1–10 scale).

^a Sleep outcomes were assessed via survey questions that asked participants to answer questions based on their typical sleep and sleep schedules over the past month.

^b There were no exposures equal to 45.

^c There were no exposures equal to 16.