The aging of a person is not only reflected in their appearance, although the face can delay aging through skincare, medical aesthetics, and other methods. However, to determine whether a person is truly beginning to age, there is another often overlooked sign of aging—sleep. As one ages, a significant change compared to younger years is the alteration in sleep quality. This change in sleep marks the process of aging, and if you don't experience any of these changes, it proves that you are still very young!

A sign of aging begins with sleep.

Reduction in sleep duration

你每天睡眠时间多久？8 小时、6 小时，还是 5 小时？随着年龄的增加，人的睡眠时长确实会减少。很多人年轻时一觉睡 8～9 小时，上了年纪后睡 5～6 小时就醒了。根据《美国睡眠医学会》的数据来看，婴幼儿所需的睡眠时间最多，随着年龄的增长，人类的睡眠时间呈现减少的趋势。2000 年《美国医学会杂志》发表了一项临床研究发现，随着年龄的增长，睡眠时间显著下降。比如，从中年阶段（36_{50 岁）到晚年阶段（71}83 岁），总睡眠时间平均每 10 年减少 27 分钟。这一变化主要发生在 50 岁之后。换句话说，50 岁之后，每过 10 年总的睡眠时长减少 27 分钟。

Experiencing fragmented sleep.

“睡眠中间醒来次数增加”“睡到后半夜总是醒，醒来又半天睡不着”……这种“碎片化睡眠”在中老年人中尤其突出。为什么中老年人更容易出现碎片化睡眠？不仅仅是人类，其实许多动物在变老时，都会有碎片化睡眠的状况出现。2022 年 2 月，斯坦福大学医学院的研究人员在国际《科学》期刊上发表的一项研究发现：大脑中“Hcrt 神经元”的活动能控制清醒和睡眠状态。随着年龄的增长 Hcrt 神经元更容易被触发，出现过度兴奋，进而导致出现“碎片化睡眠”。研究选取了两组不同年龄的小鼠，并用光刺激特定的神经元，使用成像技术记录了结果。第 1 组：年轻小鼠（3_{5 个月）第 2 组：老年小鼠（18}22 个月）研究发现，在老龄化过程中，Hcrt 神经元转变为超兴奋状态，正是这样的变化导致老年小鼠更容易出现碎片化睡眠。

The duration of deep sleep has decreased.

上了年纪，很多人都会有深睡眠时间减少的感受，比如“明明睡着了，但又感觉像没睡着”。上述《美国医学会杂志》发表的临床研究指出，正常衰老过程中，睡眠阶段的变化包括觉醒次数和觉醒时间增加，以及深度慢波睡眠减少。例如：从青年阶段（16_{25 岁）到中年阶段（36}50 岁），深度慢波睡眠的百分比从 18.9% 降至 3.4%，被较浅的睡眠所取代。研究指出，随着年龄增加生长激素分泌的下降，与深度睡眠的减少密切相关。从早年到中年，生长激素分泌显著下降（每 10 年减少 372 微克）；从 50 岁后，生长激素分泌会进一步下降每 10 年减少 43 微克。

Methods to Improve Sleep Quality

Try it for people who have poor sleep

Wearing socks to sleep.

Does wearing socks affect sleep quality and duration? A study published in the "Journal of Physiological Anthropology" in 2020 on the "Impact of Wearing Socks on Sleep" found that wearing socks while sleeping can effectively improve sleep quality. The experimental study discovered that compared to those who do not wear socks while sleeping, those who do: - Fall asleep faster: by 7.5 minutes - Wake up fewer times during sleep: 7.5 times less - Have a longer total sleep duration: extended by an average of 32 minutes - Have improved sleep efficiency: increased by 7.6% The study pointed out that this is mainly related to the body's limb temperature during sleep, as the temperature of areas like the calves and feet is easily affected by external environmental factors. Wearing socks can help maintain a comfortable and warm sleeping environment.

Cover with a heavy quilt.

Heavy blankets lead to better sleep. A study published in the Journal of Sleep Research by Swedish researchers found that sleeping under a heavier blanket increases the release of melatonin, promoting better sleep. The experimental study discovered that using a weighted blanket can increase the concentration of melatonin in saliva by approximately % compared to using a lightweight blanket.

Soak your feet before going to bed.

If you don't like wearing socks to bed, you can actually soak your feet before sleeping, as the principle is similar. An analysis study published in the "Journal of Integrative and Complementary Medicine" in a certain year and month pointed out that soaking feet in warm water 1 hour before bed can significantly improve the sleep quality of the elderly. The optimal conditions for foot soaking to enhance sleep are: water temperature at 40°C, soaking duration not exceeding 20 minutes, and water level 2 cm above the ankle. When these three conditions are met, foot soaking has the best effect on improving sleep.

Don't use your phone before going to bed.

In a sleep data survey conducted by an American sleep assessment organization involving over a thousand people, it was found that using a phone for a few minutes before bed can keep the body alert for several hours. On average, it takes an hour to fall asleep after playing with a phone for a few minutes before bed. This is because the blue light emitted by phone screens increases alertness, thereby prolonging the time it takes to fall asleep.

Do some sleep-inducing exercises.

A study published in the "British Journal of Sports Medicine" online edition found that performing these three exercises within hours before bedtime can significantly extend sleep duration. Squat: Mimic the motion of sitting in a chair, ensuring knees do not go beyond the toes. Calf raise: Stand and lift the heels to contract the calf muscles, then slowly lower the heels back to the ground. Knee lift with hip extension: Stand and lift the knee, extending the hip joint with a straight leg. Each session only requires minutes, performed every minutes. This can extend the night's sleep time by nearly minutes.