Sleep inertia 睡眠慣性

 

剛睡醒感到難以起床，睡眠醫學上稱為「睡眠慣性」，它是睡眠和清醒之間的過渡狀態，表現為暫時性的認知和動作反應遲緩，持續時間通常約20~30分鐘，不過一小時內都算正常。

Sleep inertia refers to the groggy, disoriented feeling experienced after waking up. It's a transitional state between sleep and wakefulness characterized by impaired cognitive and physical performance. Sleep inertia typically lasts around 30 minutes, but it's normal within an hour.

時型(chronotype)為夜型人(俗稱夜貓族) 與社交時差高的人 (工作日與休假日的睡眠時間中點差異 [前移或後移] 兩個小時以上) ，以及剛好在深睡期或快速動眼期被叫醒的人，都會有更明顯的睡眠慣性反應。這些人會對外在刺激 (例如鬧鐘) 的喚醒依賴程度較高。

People who are night person (owl), people with high social jet lag (more than two hours of difference between midpoint of sleep on workdays and midpoint of sleep on free days [shifts forward or backwards]), and people who wake up from deep sleep or during a REM sleep cycle can increase the likelihood of experiencing sleep inertia. These people also have a higher reliance on external stimuli (such as alarm clocks) to wake them up.

除了上述情況之外，神經疾患和憂鬱症患者，也會變得需要異常長的時間才能脫離睡眠慣性。過長的睡眠慣性時間可否作為神經/精神疾病診斷的指標，還有待釐清。對於睡眠慣性的了解，也有助於我們知道如何在睡醒之後快速開機。

In addition to the above situations, patients with neurological diseases and depression will also need an abnormally long time to break out of sleep inertia. It remains to be clarified whether prolonged sleep inertia can be used as an indicator for the diagnosis of neurological/psychiatric diseases. Nevertheless, the understanding of sleep inertia can also help people understand how to quickly start up after waking up.

睡眠慣性的原因和大腦的醒覺狀態以及神經網路連結有關；剛睡醒的時候，左右半腦的連結尚未恢復，感覺-動作網路[sensorimotor]也尚未恢復，再加上血液供應相對減少，神經與血管的耦合關係也下降，造成神經元活動與局部血流反應的狀態有時間差。這也表示，一些情況下（例如睡著與剛醒時），fMRI不見得能完全反應腦神經元活動的狀況。

The cause of sleep inertia is related to the brain's state of wakefulness and the connections within its neural network. When you just wake up, the connection between the left and right hemispheres of the brain and the sensorimotor coupling has not yet returned to daytime levels. A lack of blood flow to the brain upon awakening can lead to decreased neurovascular coupling, which causes a time lag between neuronal activity and local blood flow status. This also indicates that, in some cases (such as during sleep and awakening), fMRI may not be able to fully reflect the state of brain neuronal activity.

人在剛醒來時多少都會感到腦部血流不足，而腦血流量和腦血流速度通常最多需要 30 分鐘才能恢復到平常白天的水準。腦幹和視丘的血流會比較快恢復到清醒時的水準，約相差 15 分鐘後，大腦前半部的皮質區域也會恢復到正常的白天血流。

Normally, individuals express a lack of blood flow to the brain upon awakening. Levels of cerebral blood flow and cerebral blood flow velocities will take up to 30 minutes to increase and reach daytime levels. Cerebral blood flow returns to waking levels in the brainstem and thalamus first. After 15 minutes, the brain's anterior cortical regions receive normal daytime blood flow.

從睡眠轉到清醒的意識恢復過程，暫時是由視丘(thalamus)來主導意識，隨著時間變得更清醒時，再逐漸轉交給大腦注意力相關的神經網路。在剛睡醒的短暫期間，我們會快速的遺失夢境，可能也和這個神經網路的轉換有關。

In the process of restoring consciousness (from sleep to wakefulness), the thalamus temporarily takes over, and then gradually transfers to the attention-related brain neural network as the wakefulness lasts. During the short period after waking up, we quickly forget our dreams, which may also be related to the altering of the neural network.

需要開車或任何需要維持警覺和反應力的工作者，都必須考慮到睡眠慣性的影響。有一些基本的方法可以減低睡眠慣性：

• 確保充足的睡眠和規律的作息時間。
• 使用輕柔的鬧鐘（音量漸增，或其他不引起驚嚇的叫醒方式）。
• 拉開窗簾讓陽光照進來或開燈。光線有助於喚醒身體。
• 喝水。保持水分充足有助於提高整體的醒覺度。
• 規律運動有助於改善睡眠品質，減少睡眠慣性的可能性。
• 不要在睡前飲酒和吸菸，因為它們都會使睡眠品質變差，並加劇睡眠慣性。

People who drive or perform critical tasks (which require them to stay alert and responsive) must allow time for sleep inertia to dissipate before performing critical tasks.

There are some basic ways to reduce sleep inertia:

• Ensure sufficient sleep and a regular sleep schedule. 
• Use gentle alarm clocks (with gradually increasing sound or other non-startling methods). 
• Brighten up the room. Exposure to light can help wake up your body. 
• Staying hydrated can help improve overall alertness. 
• Avoid alcohol and smoking before bedtime, for they both can interfere with sleep quality and exacerbate sleep inertia.

夜班工作者可能會因為累了一天之後想在早上小睡一下 (想說睡一下，但又睡不到五、六小時)。強烈的睡眠驅力加上小睡時間太長 (超過一小時)，會導致更難從睡眠慣性恢復，因為這一睡很可能就進入到深層睡眠或快速動眼期了，從這樣的睡眠期醒來反而會感到更疲憊。因此，只是要小睡一下的話，尤其是在白天，建議還是不要超過一小時。

Longer periods of sleep inertia were seen in night shift workers after they took an hour long nap during the early morning hours. This was likely due to the strong drive for sleep during this time and the long nap allowing the brain to progress into deeper stages of sleep. Short naps (< 1 hour) can help to reduce the effects of sleep inertia, especially if they are taken during the day. 

曾有研究發現醒來後服用100毫克咖啡因可以減少睡眠慣性，比服用安慰劑更快恢復反應時間。而由於咖啡因需要大約30分鐘才能完全奏效，另一種方法是在短暫小睡 (30分鐘) 之前喝咖啡，這樣醒來後，就能同時體驗到咖啡因和小睡帶來的提神效果，並減少睡眠慣性。

Taking 100 mg of caffeine on awakening has been observed can reduce the time of sleep inertia, restoring reaction time more quickly compared to placebo. And due to the fact that caffeine takes about 30 minutes to reach full effect, another strategy is to take caffeine just before taking a short nap (30 min), so on awakening, the person can experience alerting benefits from both caffeine and the nap and less sleep inertia.

𓈒𓐍𓂃𓈒𓂂𖤣𖤥𖠿𖤣𖤥𓂃◌𓈒𓐍𓂃𓈒𓂂𖤣𖤥𖠿𖤣𖤥𓂃◌𓈒𓐍𓂃𓈒𓂂

「睡眠慣性」是幾週前有一次睡眠晨會的主題，我覺得蠻有趣的，因為人們可能會關切失眠睡不著的問題，而輕忽了每天我們能自然地從睡眠中醒來，是多麼神奇也值得感激的事情。

講者有提到「夜型人與社交時差嚴重者，會有更強烈的睡眠慣性反應傾向」，是依據231位年輕人（大學生）的「問卷調查」所得到的結論。而比對腦電圖(EEG)與fMRI去看神經血管耦合穩定度於醒睡期間變化的那篇研究❀，我突然想到「那不就同時貼著滿頭的導線進去fMRI裡面睡覺？」，也太酷了吧。 

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❀ 是臺北醫學大學心智意識與腦科研究所聯合台北、桃園和高雄的多家醫學中心在2019年發表的研究，檢測了80位健康成年人得到的結果。原文：Wu, C.W., Tsai, PJ., Chen, S.CJ. et al. Indication of dynamic neurovascular coupling from inconsistency between EEG and fMRI indices across sleep–wake states. Sleep Biol. Rhythms 17, 423–431 (2019).

••┈┈••

這陣子陪診的時候，坐在醫院候診區看著重複播放的衛教片，衛教片不是都會說哪些人會容易得這種病？幾歲以上的、老化、慢性病之類的。還有另外一天睡眠晨會，資深牙科醫師針對近期有傳聞說矯正牙齒會加重睡眠呼吸中止症這種事，澄清那是矯正不當造成下顎過度後縮，加上患者本身氣道的解剖空間就比較狹窄，而早期的牙科可能傾向以下巴後縮為正常咬合位去做矯正，導致呼吸空間更壓迫。除此之外，很多人沒有注意到頸椎可能有問題，長時間用電腦或滑手機，姿勢不良久而久之都會造成頸椎的排列出問題，還有，人類是二足動物直立位，頸椎就是很容易出問題。

這些事讓我腦中出現了一個畫面，就是地球就像一個密室逃脫的遊戲場，進去之前工作人員都有做說明：每個人拿到的裝備都不是很強壯，有的勉強堪用，有的甚至從一開始就頗爛。地球母親說為了提供各位靈魂最完整的物質界的制約體驗，不好意思根據你提出申請時的計劃書，你拿到的人類套裝就是這樣。但每個人都因為各自的理由簽了切結書進來了。所以才會看到各種人類解剖構造設計上的缺陷，以及整體環境讓人容易生病或意外死亡：睡覺睡一睡會呼吸道塌陷或堵塞造成缺氧，水晶體用到四、五十歲就會開始壞掉了，還年輕頸椎就壞掉了，有時間睡的時候睡不著，沒時間睡的時候睡不飽，街道沒有行人可以走的地方，夏日烈陽時沒有遮蔽物直接曝曬，人與人之間的空間不夠容易產生壓力與暴力。但地球上有「醫療」這種概念，就看各位有沒有辦法取得「醫療」以及運用它修補裝備，盡可能舒適地走完全程了。

𓂃𓇬𓈒 𓈒𓏸𓈒𓂂𓏸