Paul Michel A, Love Ryan J, Hawton Andrea, Brett Kaighley, McCreary Donald R, Arendt Josephine
Defence Research and Development Canada, Toronto, ON, Canada M3K2C9.
Defence Research and Development Canada, Toronto, ON, Canada M3K2C9.
Sleep Med. 2015 Mar;16(3):406-13. doi: 10.1016/j.sleep.2014.12.012. Epub 2015 Jan 16.
There are conflicting reports regarding seasonal sleep difficulties in polar regions. Herein we report differences in actigraphic sleep measures between two summer trials (collected at Canadian Forces Station Alert, 82.5°N, in 2012 and 2014) and evaluate exogenous melatonin for preventing/treating circadian phase delay due to nocturnal light exposure.
Subjects wore actigraphs continuously to obtain sleep data. Following seven days of actigraphic recording the subjects filled out questionnaires regarding sleep difficulty and psychosocial parameters and subsequently remained in dim light conditions for 24 hours, during which saliva was collected bihourly to measure melatonin. During Trial 2, individuals who reported difficulty sleeping were prescribed melatonin, and a second saliva collection was conducted to evaluate the effect of melatonin on the circadian system.
Trial 1 subjects collectively had late dim light melatonin onsets and difficulty sleeping; however, the Trial 2 subjects had normally timed melatonin rhythms, and obtained a good quantity of high-quality sleep. Nocturnal light exposure was significantly different between the trials, with Trial 1 subjects exposed to significantly more light between 2200 and 0200h. Melatonin treatment during Trial 2 led to an improvement in the subjective sleep difficulty between the pre- and post-treatment surveys; however there were no significant differences in the objective measures of sleep.
The difference in sleep and melatonin rhythms between research participants in June 2012 and June 2014 is attributed to the higher levels of nocturnal light exposure in 2012. The avoidance of nocturnal light is likely to improve sleep during the Arctic summer.
关于极地地区季节性睡眠困难的报道相互矛盾。在此，我们报告了两次夏季试验（2012年和2014年在北纬82.5°的加拿大军队警戒站收集）之间活动记录仪睡眠测量的差异，并评估外源性褪黑素预防/治疗夜间光照导致的昼夜节律延迟的效果。
受试者连续佩戴活动记录仪以获取睡眠数据。在进行七天的活动记录仪记录后，受试者填写关于睡眠困难和心理社会参数的问卷，随后在昏暗灯光条件下保持24小时，在此期间每两小时收集一次唾液以测量褪黑素。在试验2中，报告有睡眠困难的个体被给予褪黑素，并进行第二次唾液收集以评估褪黑素对昼夜节律系统的影响。
试验1的受试者总体上褪黑素在昏暗灯光下的起始时间较晚且存在睡眠困难；然而，试验2的受试者褪黑素节律时间正常，且获得了充足的高质量睡眠。两次试验之间夜间光照暴露存在显著差异，试验1的受试者在22:00至02:00之间暴露于显著更多的光线下。试验2期间的褪黑素治疗导致治疗前和治疗后调查之间主观睡眠困难有所改善；然而，睡眠的客观测量指标没有显著差异。
2012年6月和2014年6月研究参与者之间睡眠和褪黑素节律的差异归因于2012年较高水平的夜间光照暴露。避免夜间光照可能会改善北极夏季的睡眠。
