Can our bodies really catch up on lost sleep?
Regardless of who you are, when you get less than seven hours of sleep, you start accumulating what's known as sleep debt or sleep deficit. The Sleep Foundation defines it as the difference between the amount of sleep someone needs and the amount they actually get.
Now, when you're in sleep debt, your body sends out a variety of warning signs. Think drowsiness, irritability, impatience, dull skin, dark circles, memory lapses, trouble concentrating, reduced libido or headaches, for example.
In the long run, it hinders mental and physical recovery, weakening the immune system, affecting appetite and even potentially leading to cardiovascular issues. Rest assured, No sleep debt is irreversible, but bear in mind that even a single hour's lost sleep can take up to four days to recover from, according to research published in Scientific Reports in 2016.
What can I do in the short term if I notice such symptoms?
Try to get a little more sleep than usual in the days following, especially if you start getting an urge to nap during the day. But you don't want to overdo it. Limit yourself to an extra hour at most. If practical, a short nap of 20 to 30 minutes in the early afternoon can be beneficial. It helps restore alertness and reduce cardiovascular risks, as we've discussed on the show before when talking about power naps.
Can't I just lie in on the weekend?
Sadly not, that's a common misconception. The problem is that a late lying can disrupt your body's natural rhythm, which thrives on consistency. You might end up staying up late again and cutting your sleep short on Monday morning when you have to wake up early. It can easily end up becoming a vicious cycle, so an extra hour's sleep may be viable on the weekend, as in the week. But it shouldn't be a repeat or go-to solution. It's best avoided if you have ongoing sleep issues too.
So how can we make up for lost sleep without disrupting our biological clock?
The most important step is to establish good sleep hygiene. That means maintaining regular wake-up and bedtimes, and optimising your environment and habits to support falling asleep easily. Avoid coffee, tea, alcohol and tobacco too late in the day, and try not to eat a heavy meal late in the evening. Turn off all electronic devices at least an hour and a half before bed. Trust me, reading is a more relaxing alternative bedtime activity.
Ensure your bedroom isn't too warm and that you have comfortable bedding. The goal is to sleep well throughout the week, consistently and sufficiently, so you don't accumulate sleep debt to start with. In the morning, expose yourself to natural light as soon as possible to help regulate your biological clock.
Finally, keeping a sleep journal can be a useful tool for self-assessment, helping you track your sleep habits and any sleep debt symptoms. That will also come in handy if you do ever need to see a healthcare professional for sleep problems. There you have it.
词汇表
sleep debt [det] n. 睡眠债（指实际睡眠时间少于所需睡眠时间的差额）
sleep deficit [ˈdefɪsɪt] n. 睡眠赤字，睡眠不足（同sleep debt）
drowsiness [ˈdraʊzinəs] n. 困倦，睡意
irritability [ˌɪrɪtəˈbɪləti] n. 易怒，暴躁
impatience [ɪmˈpeɪʃns] n. 急躁，不耐烦
dull skin [dʌl] n. 皮肤暗沉（皮肤缺乏光泽、显得无生气的状态）
dark circles n. 黑眼圈
memory lapses [læpsɪz] n. 记忆力减退，记忆断层
libido [lɪˈbiːdəʊ] n. 性欲，性冲动
hinder [ˈhɪndə(r)] vt. 阻碍，妨碍
immune system [ɪˈmjuːn] n. 免疫系统
cardiovascular [ˌkɑːdiəʊˈvæskjələ(r)] adj. 心血管的
rest assured [əˈʃʊəd] （用于安慰某人）请放心，别担心
irreversible [ˌɪrɪˈvɜːsəbl] adj. 不可逆转的，无法挽回的
overdo [ˌəʊvəˈduː] vt. 做得过分，过度
alertness [əˈlɜːtnəs] n. 警觉，清醒，机敏
power nap [næp] n. 能量小睡，恢复精力的小睡
lie in 睡懒觉，晚起
misconception [ˌmɪskənˈsepʃn] n. 误解，错误观念
natural rhythm n. 自然节律（指人体内在的生物钟和生理节律）
thrive on [θraɪv] 依赖…而成功，在…蓬勃发展
consistency [kənˈsɪstənsi] n. 连贯性，一致性，规律性
vicious cycle [ˈvɪʃəs] n. 恶性循环
viable [ˈvaɪəbl] adj. 可行的，可实施的
go-to solution n. 首选解决方案，首选之策
biological clock [ˌbaɪəˈlɒdʒɪkl] n. 生物钟，生理时钟
sleep hygiene [ˈhaɪdʒiːn] n. 睡眠卫生（有助于改善睡眠的习惯和环境条件）
tobacco [təˈbækəʊ] n. 烟草，烟叶
bedding [ˈbedɪŋ] n. 床上用品，寝具
come in handy [ˈhændi] 派上用场，迟早有用
healthcare professional [ˈhelθkeə prəˈfeʃənl] n. 医疗专业人员（如医生、护士等）
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