How much black coffee can you drink a day? What is the reason for drinking coffee to be sleepy or energetic?

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When I started to watch the drama after work, I only agreed to watch one episode but turned into watching hundreds of millions of episodes. Living in the Chinese time zone, but living in the American time zone. At dawn, he went back to the office with dark circles under his eyes and relied on coffee to continue his life. But is this really realistic?

It is well known that lack of sleep can damage a person's cognitive process. For example, if people are inattentive, the error rate at work will also increase. There is no lack of examples of serious mistakes due to lack of sleep in life. On May 14, a driver in Sichuan Province crashed due to fatigue driving, resulting in six deaths and 28 injuries to varying degrees.

Lack of sleep is not a problem that everyone can solve. According to People's Daily's report in March 2019, more than 300 million people in China have sleep disorders, and the incidence of insomnia among adults is nearly 40%. The 2020 China Sleep report directly announced that the average Chinese sleep time is only 6.82 hours. In the case of lack of sleep, most people will choose drinks that contain caffeine to refresh themselves. But how much can caffeine affect productivity?

Recently, in the latest issue of the academic Journal of Experimental Psychology: learning, memory and Cognition, a study conducted by the Sleep and Learning Lab of Michigan State University assessed the effect of caffeine in counteracting the negative effects of sleep deprivation on cognition, which is different from what people usually think: caffeine can only relieve drowsiness caused by lack of sleep. However, performance in some difficult tasks is still affected.

In this study, the researchers recruited 276 participants who were asked to complete a simple attention task (PVT) and a more challenging task (UNRAVEL) in a specific order without skipping or repeating steps.

The participants were randomly assigned to sleep at home or to repair immortals in the laboratory. In the morning, participants were recalled to the lab to take a capsule containing 200 milligrams of caffeine or a placebo. After waiting for a period of drug absorption, all participants were asked to complete two tasks again.

Among the sleep-deprived participants, those who took a placebo did not perform well on either task, while those who consumed 200mg of caffeine were competent in a simpler PVT task, but caffeine intake did not improve their performance when it came to challenging UNRAVEL tasks.

As a result, caffeine improves people's ability to stay awake and focus on a task. However, when it comes to more complex tasks that require a high level of attention, caffeine has few positive effects. It also confirms that sleep is very important for people who need to perform high-risk procedures, such as surgeons, police officers, drivers and so on.

Although coffee, as a substitute for sleep, solves the problem of sleep deprivation in some ways, its impact is only short-lived and limited. But when you can't sleep any more, coffee is still a good choice.

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