A cup of coffee can make a refreshing and cheer up, but also lead to the sleepless at nights. According to the latest report of the United States of "daily health news", "Sleep Medicine" magazine published in the United States a new study, it found that caffeine only affects "lark" type crowd who accustomed to go to bed early and get up early, but it did not interfere the people who are staying up late.
In the new study, Stanford University researchers asked 50 college students record their caffeine intake condition in the week, along with the sleep and wake time. Students worn a device on the wrist to detect the physical activities, and the device is able to record a clear position in the test takers to sleep at night. The researchers also measured the level of caffeine in the week of each tested students’ saliva.
It was found that the type of person "lark" who intake caffeine during the day are easier to wake up at night and be interrupted by the sleep. The researchers said the new study found that caffeine intake has the relationship with time types (the most alert or active time period of people in a day).
The person in charge of the new study, an associate professor of psychiatry and behavioral sciences, Jamie Dr. Cai Cile said, most college students lack of sleep, no matter how much they drink coffee, they can fell down asleep quickly. For "lark" type of person, if they intake more caffeine, they will be refreshing during the sleep process at night. This did not reflect on the "night owl" type of person.
The next step of study will be expand the same study to adults to make sure that the caffeine only effect "lark" type people.
Dr. Cai Cile said that everyone has the different metabolism condition of caffeine in the body. Some people can metabolism of caffeine within a few hours; some people drink coffee at noon, at the evening, the caffeine still in the body.
Therefore, if you belong to the "Lark" type, then it is best not to intake of too much coffee or tea and other caffeinated beverages after noon.