How long should we sleep?

Everyone know the importance of sleeping. However, how long should we actually sleep a day? The answer to this question depends on how old we are. Roughly speaking, the older we are, the less time we need to sleep.

According to National Sleep Foundation. The most suitable time a child who is between 6 and 13 years old sleep is 9~11 hours a day. Teenagers between 14 and 17 should sleep 8~10 hours every day. People between 18 and 64 have to sleep 7~9 hours each day. And the elderly whose age is above 65 is recommended to sleep 7~8 hours a day.

If we don't get enough sleeping, some of the following things will likely to happen. First of all, we will be in bad temper. Second, we may eat too much because our bodies need more energy. Last but not least, we will more likely to get a cold because our immune system have not enough time to do its job.

However, I don't think it is easy to get enough sleeping every day. For example, I sleep only three hours yesterday...
Sad story.

Reference: Hirshkowitz M, et al, National Sleep Foundation’s sleep time duration recommendations: methodology and results summary, Sleep Health (2015)