鐘雷霆

If youre one of those people who has trouble falling asleep， listen up. You might fall asleep 15 minutes earlier and wake up far less during the night if you put on a pair of socks at bedtime.

To understand why， you first need to grasp the relationship between core body temperature and sleep. During daylight hours， the human body hums along at an average temperature of 98.6 degrees Fahrenheit （37 degrees Celsius）. But at night， your core body temperature dips as much as 2 degrees Fahrenheit （1.2 degrees Celsius） over the course of six or seven hours of sleep.

This gradual decrease in core body temperature， it turns out， is a key part of the complicated neurobiological dance of falling asleep and staying asleep. And the faster you can lower the core body temperature， the faster you will fall asleep.

One of the ways that your body regulates its temperature is through blood vessels in your skin. If the brain decides the body is too hot， it will dilate （widen） blood vessels（vasodilation）， redistributing warmer blood from the bodys core through the rest of the body to cool it down. If the body is too cold， the brain signals the opposite reaction， restricting the flow of blood to the surface （vasoconstriction）.

The palms of your hands and soles of your feet are the bodys most efficient heat exchangers， since they are hairless and less insulated than other skin surfaces. Researchers have shown that warming the feet before going to sleep using a warm foot bath or by wearing socks promotes vasodilation， which in turn lowers the bodys core temperature faster than going to sleep with cold， bare feet.

Scientists hypothesize that socked feet have a neurological effect as well. The brains“thermostat”is located in a region called the preoptic/anterior hypothalamus （PO/ AH）. Inside the PO/AH is a type of neuron called a warmsensitive neuron （WSN） that increases its firing rate when theres a temperature difference between the bodys core and extremities like the feet.

Its a bit of a chicken and the egg situation， but research has shown that WSN firing rates go way up on the onset of slow wave or“deep”sleep and gradually decrease prior to waking up. So WSNs may play a role in generating the sensation of sleepiness that helps us fall asleep and stay asleep. And if thats the case， warming up the feet before bedtime gives WSNs an extra boost.

In a small study， Korean researchers found that wearing a pair of special“sleeping socks”not only sped up the onset of sleep， but increased overall sleep time by an average of 30 minutes and cut nighttime waking episodes in half.

If youre worried about becoming too warm while wearing socks in bed， look for ones made of natural breathable fibers.

如果你入睡困難，注意，穿襪子睡覺(jué)可能讓你提前15分鐘進(jìn)入夢(mèng)鄉(xiāng)，晚上醒來(lái)的次數(shù)也會(huì)少得多。

要理解其中原因，你需要首先掌握核心體溫和睡眠之間的關(guān)系。白天，人體的平均體溫為37攝氏度。但是在晚上，在六到七個(gè)小時(shí)的睡眠過(guò)程中，核心體溫會(huì)下降1.2攝氏度。

事實(shí)證明，核心體溫的逐漸下降是入睡和保持睡眠這一復(fù)雜的神經(jīng)生物學(xué)行為的關(guān)鍵部分。核心體溫的下降速度越快，你就越快入睡。

身體調(diào)節(jié)體溫的方法之一是通過(guò)皮膚中的血管。如果大腦認(rèn)為身體太熱，會(huì)擴(kuò)張血管，將溫暖的血液從身體核心重新分配到身體其他部位，使其降溫。如果身體太冷，大腦會(huì)發(fā)出相反的反應(yīng)信號(hào)，限制血液流向皮膚表面（血管收縮）。

手掌和腳底是身體最有效的散熱器，因?yàn)榕c其他位置的皮膚相比，手掌腳底光滑無(wú)毛、絕緣性差。研究人員已經(jīng)表明，睡前泡腳或穿襪子暖腳可以促進(jìn)血管擴(kuò)張，這樣會(huì)比赤腳冷著睡覺(jué)更快地降低身體的核心溫度。

科學(xué)家們推測(cè)，腳上穿襪子也會(huì)對(duì)神經(jīng)系統(tǒng)產(chǎn)生影響。大腦的“恒溫器”位于視前區(qū)/下丘腦前部（PO/AH）。在視前區(qū)/下丘腦前部存在熱敏神經(jīng)元（WSN），當(dāng)身體核心和四肢（如腳）之間存在溫差時(shí)，該神經(jīng)元會(huì)增加其放電頻率。

這有點(diǎn)像雞和蛋的關(guān)系，但研究表明，熱敏神經(jīng)元的放電頻率在慢波睡眠或“深度”睡眠開始時(shí)會(huì)升高，在醒來(lái)之前會(huì)逐漸降低。因此，熱敏神經(jīng)元可能在產(chǎn)生睡意方面發(fā)揮作用，幫助我們?nèi)胨⒈３炙?。如果是這樣的話，就寢前讓腳變熱能給熱敏神經(jīng)元帶來(lái)額外的動(dòng)力。

在一項(xiàng)小型研究中，韓國(guó)研究人員發(fā)現(xiàn)，穿一雙特殊的“睡襪”不僅加快了入睡過(guò)程，而且平均增加了30分鐘的總睡眠時(shí)間，夜間醒來(lái)的次數(shù)減少了一半。

如果你擔(dān)心睡覺(jué)穿襪子太熱，那就找一雙透氣的天然材質(zhì)襪子。