Most effective ways to improve deep sleep 如何增加深層睡眠

 「深層睡眠」是非快速動眼睡眠的第三階段，特徵是腦波出現明顯的慢波。在此階段，副交感神經系統會占主導地位，降低心率、呼吸頻率和代謝需求，而交感神經系統則受到抑制。

這種自律神經的轉換是為了停止日常損耗，降低能量消耗，身體才能啟動組織器官和免疫系統的修復工作。交感神經系統被抑制，能讓心血管系統休息，幫助身體從白天的壓力中復原。

健康的成年人，深層睡眠會佔整晚睡眠時間的15%～ 25%。

“Deep sleep” is the third stage of non-rapid eye movement sleep with distinctive slow-wave. During this phase, the parasympathetic nervous system dominates, significantly slowing heart rate, breathing rates, and metabolic demand, while the sympathetic nervous system is suppressed. 

This halts daily wear and tear, lowering energy expenditure to power physical recovery, tissue repair, and immune system reinforcement. The suppression of sympathetic nervous system allows your cardiovascular system to rest and recover from daytime stress.

Deep sleep typically comprises 15% to 25% of a healthy adult’s total night's rest.

上圖是一個睡眠片段化的案例，可以看到綠色的慢波睡眠相當少，睡眠相當破碎，而且幾乎沒有深層睡眠。（本人不一定記得自己有醒來或做夢，只會覺得沒睡飽）

除了睡眠階段圖，睡眠片段化也會顯示在高比例的WASO。WASO就是入睡後又醒來的時間，WASO > 30分鐘就是具有臨床意義的睡眠片段化，而WASO > 60分鐘則代表嚴重失眠。

The image above is a typical example of fragmented sleep. You can see that there is very little slow-wave sleep (in green), the sleep is quite fragmented, with frequent arousals, and there is almost no deep sleep. (the person may not even remember dreaming or waking up, but just feel like didn't get enough sleep.)

In addition to the sleep stage diagram, sleep fragmentation is also revealed as high level of WASO (wake after sleep onset). WASO exceeding 30 minutes is typically considered a sign of clinically significant sleep fragmentation, while a total WASO of more than 60 minutes often points to severe insomnia.

深層睡眠對記憶力和大腦健康很重要。因為大腦必須在深層睡眠期間進行「記憶鞏固」和「清潔」。神經元會選擇性地修剪掉不必要的神經連接，強化重要的連接，並將新獲取的訊息從海馬迴（臨時儲存）轉移到新皮質層（永久存放）。這是在確保大腦不會被瑣碎的細節所淹沒。

同時，腦中的神經元以及膠質細胞會在深層睡眠時略微縮小體積，讓大腦能夠沖刷清除代謝廢物。

總而言之，深層睡眠具有保護認知功能和長期記憶的重要功能。

Deep sleep is vital for memory and brain health, too. It’s when the “memory consolidation” and “brain cleanup” takes place. The brain neurons selectively prunes away unnecessary neural links and strengthens important ones, and transferring newly acquired information from the hippocampus (temporary storage) to the neocortex (permanent storage). This ensures your brain doesn’t become oversaturated with trivial details. 

Meanwhile, the brain neurons and glial cells slightly shrink in size, which allows the brain to flush out metabolic waste. 

Overall, deep sleep protects cognitive function and long-term memory.

以下是六種最有效、有科學根據的自然改善深度睡眠的方法：

1. 持續的運動習慣，也就是將中高強度的有氧運動納入日常生活中。身體是現實的，如果你白天讓它安靜地像個雕像，它晚上就不會覺得自己需要「深度修復」。適度的中高強度運動（快走或慢跑）是最好的天然催眠劑，可以增加身體的睡眠驅力，並在你入睡後誘導出慢波睡眠來修復肌肉。
但請務必確保在睡前至少 3-4 小時之前做完較高強度的運動。因為要是運動時間太接近睡覺時間，升高的皮質醇反而會延後大腦進入深層睡眠。

Here are six most effective, evidence-based methods to naturally maximise deep sleep time:

1. Exercise consistently, make engaging in moderate-to-vigorous aerobic exercise part of your routine schedule. The body is unfilteredly honest; if you let it rest like a statue during the day, it won't feel the need for “deep repair” at night. Moderate to high-intensity exercise (brisk walking or jogging) is the best natural sleep aid, which increases your body’s sleep drive and induces slow-wave activity to repair muscles.
Just make sure to complete vigorous workouts at least 3–4 hours before bed. Exercising too late elevates cortisol and delays deep sleep onset.

2. 保持臥室涼爽。夏天將冷氣溫度設在 25–27°C 加個風扇流通空氣，冬天則維持室溫在 16–18°C之間，並且在睡前 1–2 小時洗個熱水澡或淋浴，這可以讓你的核心體溫變化更傾向於入睡。
因為深度睡眠發生在核心體溫下降時。熱水澡會促使血液流向四肢；洗澡後身體迅速降溫，就是向大腦發出訊號，表示該睡覺並進入深度恢復狀態了。

2. Keep your bedroom cool. Set your AC to 25-27 °C with a fan running to keep the air moving in summer/hot weather; while in winter/cold weather, keep the temperature between 16-18 °C.

And consider taking a warm bath or shower 1–2 hours before bed to optimize your core body temperature.
Because deep sleep occurs when your core body temperature drops. A warm bath forces blood to your extremities; as you exit the water, your body rapidly cools, signaling to your brain that it is time to sleep and enter deep recovery.

3. 每天起床後一小時內，花 10-15 分鐘曬曬晨光，並且每天（包括週末和假日）都在同一時間起床，這樣可以穩定你的晝夜節律。
晨光可以穩定你的生理時鐘，確保大腦在正確的時間分泌褪黑激素。規律的作息可以增強睡眠驅力，在入睡後帶來更深層的睡眠。

3. Anchor your circadian rhythm by exposing yourself to 10–15 minutes of direct morning sunlight within an hour of waking up, and wake up at the exact same time every day (including weekends and holidays).
Morning light anchors your internal clock, ensuring your brain produces melatonin at the right time. Consistency builds a stronger sleep drive, which correlates with deeper sleep cycles.

4. 下午三點後，請對咖啡因說不。你以為咖啡因只是提神，其實它正在你體內舉辦一場為期八小時的狂歡派對，而狂歡後的代價就是剝奪你的深度睡眠。
許多人愛在睡前喝點威士忌（或其他酒類），但這是個美麗的誤會。酒精或許能讓你放鬆、更快失去意識（醉倒），但它會無情地摧毀你上半夜的深層睡眠結構，並讓你接下來的睡眠破破碎碎，隔天醒來像個在包包裡被壓扁的三明治。

4. After 3 PM, say no to caffeine. You might think caffeine is just a pick-me-up, but it's actually throwing an eight-hour party inside your body, and the price of that party is the loss of your deep sleep.
Many people love to have a glass of whiskey (or other alcoholic beverage) before bed, but this is a beautiful misconception. Alcohol might make you relax (buzzed) and lose consciousness faster (getting drunk), but it ruthlessly destroys the deep sleep structure in the first half of the night and causes fragmented sleep later, leaving you feeling like a crushed sandwich in the bag when you wake up the next day.

5. 睡前2-3小時避免食用油膩、高糖或高脂肪的食物。

深夜的消化會導致體溫升高，血糖波動也會使壓力荷爾蒙升高，這會擾亂你的睡眠週期。

5. Avoid heavy, greasy, or high-sugar meals 2–3 hours before sleep. 

Late-night digestion spikes your core body temperature and activates stress hormones as blood sugar fluctuates, which fragments your sleep cycles.

6. 如果你睡眠時間充足但仍感覺疲憊，請諮詢睡眠專科醫師，以安排相關的睡眠檢查。

阻塞性睡眠呼吸中止症是影響深度睡眠最常見卻未被診斷出來的疾病之一。在深度睡眠期間，呼吸道肌肉會放鬆；而若是患有睡眠呼吸中止症，你的身體會為了自我保護而不斷的突然將你從深度睡眠中拉出來，讓你醒來呼吸。

6. If you get enough total sleep but still feel unrefreshed, consult a doctor about getting a sleep test.

Obstructive sleep apnea is one of the most common undiagnosed medical conditions destroying deep sleep. During deep sleep, your airway muscles relax; if you have sleep apnea, your body will have to constantly pull you out of deep sleep to gasp for air.

 ✧ʕ̢̣̣̣̣̩̩̩̩·͡˔·ོɁ̡̣̣̣̣̩̩̩̩✧

恭喜你又浪費了三分之一的人生！但至少我們能把它升級為「深層修復模式」。

Congratulations on wasting another third of your life! But at least we can upgrade it to "deep repair mode".