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暗期は、長い睡眠ブロックがない状態で概日リズムを安定させ、[[Wikipedia:Slow-wave sleep|SWS]]の質を高める方法です。また、特定の健康問題が発生するのを防ぐこともできます。ほとんどのスケジュールでは、暗期は夜の（SWSピークに近い）睡眠ブロックの1〜3時間前（ほとんどの場合は2時間前が推奨）に開始し、その後約8〜12時間継続します。

Dark period is a way for sleepers to stabilize their circadian rhythms in the absence of long blocks of sleep and increase the quality of [[Wikipedia:Slow-wave sleep|SWS]]. It also prevents certain health issues from arising. For most schedules, it should start 1-3 hours (2h is recommended in most cases) before the dusk (SWS peak) sleep block and continue for around 8 to 12 hours afterwards.

==根拠==

==根拠==

現代人は夜に電気をつけることが多い。これは、すでに真夜中であってもかかわらず、体がまだ昼間だと勘違いしてしまうため、日に日に眠くなる時間が遅くなる理由の一部です。<ref name="Joo2017" />単相睡眠の場合では、長い睡眠時間の間でやや短い暗期を維持することで、概日リズムを比較的安定に保てます。

Modern humans often use electric lighting during the night. This can cause difficulty as the body thinks it is still daytime even if it is already midnight, and is part of the reason why people often experience the desire to sleep later and later each day.<ref name="Joo2017" /> For monophasic sleepers, a somewhat short dark period can be maintained during their long sleep hours, which keeps their circadian rhythms relatively stable.

しかし、このような長い睡眠ブロックを持たない多相睡眠者にとっては、これは問題となります。人工光が24時間存在するため、[[wikipedia:Melatonin|メラトニン]]の生成が抑制され、SWSの質が低下してしまいます。これでは概日リズムの乱れからさまざまな健康問題につながるため、適応を余計に難しくしますし、不健康にもなります。<ref name="pmid25635592" />そうならないためには、多相睡眠者（および単相睡眠者も）は、青、緑、または白（青と緑の両方を含む）の光が目に入らない暗期を設ける必要があります。

However, for polyphasic sleepers who might not have such long sleep blocks, this poses an issue. As artificial light is present around the clock, [[wikipedia:Melatonin|melatonin]] production is suppressed and the quality of SWS is compromised. This causes extra difficulty in adaptation and is also unhealthy, as circadian disruption is linked to various health issues.<ref name="pmid25635592" /> To avoid this, polyphasic sleepers (and monophasic sleepers too) should practice a dark period, during which no blue, green or white (as this contains both blue and green) light should enter the eye.

==タイミング==

==タイミング==

暗期の最適なタイミングは、スケジュールによって異なります。ほとんどのスケジュールでは、'''夕方・夜'''の睡眠の約1〜3時間前（デフォルトでは2時間前）に開始する必要があります（[[Special:MyLanguage/Everyman|エブリマン]]ではコア、[[Special:MyLanguage/Dual core|二主相]]と[[Special:MyLanguage/TC1|TC1]]と[[Special:MyLanguage/TC2|TC2]]では最初のコア、そして[[Special:MyLanguage/Triphasic|三主相]]では夕方のコア）。

The optimal timing of dark period depends on your schedule. For most schedules, it should begin around 1-3 hours (the default recommendation is 2 hours) before your '''dusk/evening''' sleep (core for [[Special:MyLanguage/Everyman|Everyman]], first core for [[Special:MyLanguage/Dual core|Dual core]], [[Special:MyLanguage/TC1|TC1]], and [[Special:MyLanguage/TC2|TC2]], and evening core for [[Special:MyLanguage/Triphasic|Triphasic]].

* [[Special:MyLanguage/E1|E1]]と[[Special:MyLanguage/Siesta|シエスタ]]の場合では、コアの前に開始し、目覚めた直後に終了します。

* For [[Special:MyLanguage/E1|E1]] and [[Special:MyLanguage/Siesta|Siesta]], it should start before core and end immediately upon waking.

* [[Special:MyLanguage/E2|E2]]、[[Special:MyLanguage/E3|E3]]（延長含めて）、[[Special:MyLanguage/E4|E4]]では、最初の仮眠がコアから5時間以内であれば、その仮眠が終わるまで続きます。

* For [[Special:MyLanguage/E2|E2]], [[Special:MyLanguage/E3|E3]] (including extended), and [[Special:MyLanguage/E4|E4]] it should last until the end of first nap as long as that nap is within 5 hours of the core.

* [[Special:MyLanguage/Segmented|分割]]と[[Special:MyLanguage/Dual core|二主相]]の場合、12時間を超えない範囲で、コアギャップ（三主相ではコア1とコア2のギャップ）全体をカバーするべき。

* For [[Special:MyLanguage/Segmented|Segmented]] and [[Special:MyLanguage/Dual core|Dual core]], it should cover the entire core gap (gap between first and second core for Tri core), so long as it does not exceed 12 hours.

==メカニズム==

==メカニズム==

[[File：Melanopic.png | thumb]]

[[File:Melanopic.png|thumb]]

光感受性網膜神経節細胞（ipRGC）は、その性質上、松果体によるメラトニンの分泌を制御する。それらの光に対する感度は、目の中の錐体と桿体によって提供される通常の視覚とは独立しています。ipRGCの感度は480nmでピークに達し、両側で低下します。<ref name="cie15" />暗期には、すべての光がメラトニンをある程度抑制するため、光を完全に避けることが望ましいが、多くの人のライフスタイルにとって合理的ではありません。むしろ、できるだけ明るい光を避け、必要な黄色、オレンジ、赤の光だけに限定して、メラトニンの抑制を可能な限り抑えるのがベストです。  

The intrinsically photosensitive retinal ganglion cells (ipRGCs) controls the secretion of melatonin by the pineal gland. Their sensitivity to light is independent from normal vision, which is mediated by cones and rods in the eyes. The ipRGCs have a peak sensitivity at 480 nm and drops off on both sides.<ref name="cie15" /> During the dark period it is preferable to avoid light altogether, as all light provides some melatonin suppression, but this is not reasonable for most people's lifestyles. Instead, is best to simply avoid as much bright light as possible, and limit light intake to only necessary yellow, orange and red light in order to limit melatonin suppression as much as possible.

</div>  

==方法==

==方法==

==参考文献==

==参考文献==

{{reflist|refs=

{{reflist|refs=

<ref name="Joo2017">{{cite journal |vauthors=Joo EY, Abbott SM, Reid KJ, Wu D, Kang J, Wilson J, Zee PC |date=April 2017 |title=Timing of light exposure and activity in adults with delayed sleep-wake phase disorder |url=https://www.sciencedirect.com/science/article/abs/pii/S1389945716302295 |journal=Sleep Medicine |volume=32 |pages=259-265 |doi=10.1016/j.sleep.2016.09.009}}</ref>

<ref name="Joo2017">{{cite journal |vauthors=Joo EY, Abbott SM, Reid KJ, Wu D, Kang J, Wilson J, Zee PC |date=April 2017 |title=Timing of light exposure and activity in adults with delayed sleep-wake phase disorder |url=https://www.sciencedirect.com/science/article/abs/pii/S1389945716302295 |journal=Sleep Medicine |volume=32 |pages=259-265 |doi=10.1016/j.sleep.2016.09.009}}</ref>

<ref name="Wolff2019">{{cite journal |vauthors=Wolff CA, Esser KA |date=2019 |title=Exercise timing and circadian rhythms |journal=Current Opinion in Physiology |volume=10 |pages=64-69 |doi=10.1016/j.cophys.2019.04.020 |issn=2468-8673}}</ref>

<ref name="Wolff2019">{{cite journal |vauthors=Wolff CA, Esser KA |date=2019 |title=Exercise timing and circadian rhythms |journal=Current Opinion in Physiology |volume=10 |pages=64-69 |doi=10.1016/j.cophys.2019.04.020 |issn=2468-8673}}</ref>

}}

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[[Category:Lifestyle]]

[[Category:Lifestyle]]

{{TNT|Polyphasic Lifestyle}}

{{TNT|Polyphasic Lifestyle}}