Sleep and the endogenous melatonin rhythm of high arctic residents during the summer and winter

Paul, Michel; Love, Ryan J.; Hawton, Andrea; Arendt, Joséphine

doi:10.1016/j.physbeh.2015.01.021

Cited by 31 publications

(21 citation statements)

References 28 publications

(29 reference statements)

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“…The higher winter mortality we report in this study agrees with similar studies in other patient populations . However, this seasonal variation was itself variable and only occasionally reached significance, which we think suggests the interaction of another cyclic phenomenon, for instance, temperature, sun exposure (influencing vitamin D and melatonin levels) or viral infections . However, visual comparison of local temperature, precipitation and duration of sunshine did not present resemblances.…”

Section: Discussionsupporting

confidence: 90%

Associations of postoperative mortality with the time of day, week and year

et al. 2018

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Studies that have investigated circadian, weekday and seasonal variation in postoperative mortality have been relatively small or have been for scheduled surgery. We retrospectively tested a large mixed surgical cohort from a German tertiary care university hospital for the presence of cyclical variation in all-cause in-hospital mortality after operations performed between 2006 and 2013. We analysed mortality rates after 247,475 operations, adjusted for age, sex, comorbidities, location, urgency and duration of the surgery, and intra-operative blood transfusions. The mortality odds ratio (95%CI) after operations started in the morning (08:00-11:00) were lowest, 0.73 (0.66-0.80), p < 0.001 and highest for operations started in the afternoon (13:00-17:00), 1.29 (1.18-1.40), p < 0.001. Mortality at the weekend was the same as during the week. There was no seasonal variation in mortality, p = 0.12. However, the interference of four-yearly and ten-monthly cycle amplitudes resulted in higher mortality odds ratio (95%CI) in winter 2008-2009, 1.41 (1.18-1.69), p < 0.001, and lower mortality in spring 2011 and 2012, 0.70 (0.56-0.85) and 0.67 (0.53-0.85), p < 0.001 and p = 0.001, respectively. The ability to predict cyclical phenomena would facilitate the design of interventional studies, aimed at reducing mortality following surgery in the afternoon and when cycles interfere constructively.

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Section: Discussionsupporting

confidence: 90%

Associations of postoperative mortality with the time of day, week and year

et al. 2018

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“…Our findings indicate a high prevalence of poor sleep quality, increased sleep onset latency (SOL), as well as a widespread use of sleep aids among our sample of Arctic workers during a summer period of increased sunlight. Findings are consistent with previous research in Arctic and subarctic environments during the summer months [16,17]. The mean sleep quality score for the sample was above the clinical cut off (>5) [19], indicating poor sleep quality.…”

Section: Discussionsupporting

confidence: 89%

“…Some sleep disturbances may also worsen during the summer months in polar regions. Paul et al [17] found that their Arctic sample of Canadian Forces personnel experienced statistically significantly decreased sleep duration (at 50 min) during summer versus winter months. Thus, in Arctic, Antarctic and subarctic environments during seasonal periods of increased natural sunlight, increased day length has been associated with an increased SOL [11,16], decreased sleep duration [17], poor sleep quality [18] and increased insomnia symptomatology [14].…”

Section: Introductionmentioning

confidence: 98%

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

Lubas

Maduro

Szklo-Coxe

2019

International Journal of Circumpolar Health

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Few evidence-based recommendations exist for maintaining healthy sleep during Arctic summers. Our study aimed to examine associations between sleep hygiene, sunlight exposure and sleep outcomes in workers living in and/or near the Arctic Circle during a 24-h light period. A survey was administered July 2017 to 19 workers at 3 Arctic base camps in Northeastern Alaska. Participants with poorer sleep hygiene reported increased sleepiness (r=.62, p=0.01); this correlation remained moderately strong, albeit not statistically significant (NS), after controlling for shift work (r=.46, p=0.06). No other statistically significant correlations between sleep hygiene and sleep outcomes were found. Weekly daytime (<8pm) and evening (>8pm) sunlight exposures, estimated from daily self-reported sunlight exposures for a typical workday and day off, were dichotomised, based on means, into: longer (>45 h/week) versus shorter (<45 h/week) daytime exposures, and longer (>16 h/week) versus shorter (<16 h/week) evening exposures. Participants reporting longer, versus shorter, weekly daytime sunlight exposure had statistically significantly (Mann-Whitney U=18.00, Z= −1.98, p≤0.05) decreased median sleep duration (6 h, 18 min versus 8 h, respectively) during the past month. Correlations of r≥.3 for longer, vis-à-vis shorter, daylight sunlight exposure suggest it could be related to poorer sleep outcomes, such as insufficient sleep and sleep quality, yet, as these correlations were NS, future work is needed to determine this. Weak or no correlations (and NS differences) were found for longer, versus shorter, weekly evening sunlight exposure and sleep outcomes. Findings support previous research suggesting self-regulation behaviours alone are not protective against poor sleep in Arctic environments. Sleep outcomes did not differ statistically significantly by evening sunlight exposure length. Longer weekly daytime sunlight exposure, versus shorter, was significantly associated with decreased sleep duration. Results from this exploratory study should be confirmed in studies using larger sample sizes.

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“…In addition, light exposures uniformly suppress melatonin production in insects and mammals; thus, melatonin is known as the chemical expression of darkness in animals (Hardeland and Poeggeler, 2003;Paul et al, 2015). However, studies of daily fluctuations of melatonin levels in plants have demonstrated contrasting results.…”

Section: Discussionmentioning

confidence: 99%