فَضَرَبْنَا عَلَى آذَانِهِمْ فِي الْكَهْفِ سِنِينَ عَدَدًا– الكهف: 11
So We sealed their ears [with sleep] in the cave for a number of years. (Quran 18:11)
The original Arabic of the phrase “We sealed their ears” in the Qur’an is the verb daraba. This bears the metaphorical meaning of “We have made them sleep.” Used in reference to the ears, daraba means “preventing the ears from hearing.” The fact that only the sense of hearing is mentioned here is very significant.
According to recent scientific discoveries, the ear is the only sensory organ active while a person is sleeping. This is why we need an alarm clock to wake up. 
The wisdom of the phrase “We sealed their ears” is, in all probability, that Allah closed the hearing of the young people in question, for which reason they remained asleep for many years.
As you can see that every word of Quran is full of wisdom. Sometimes it opens a door to a great truth with a single word and hence proves that this is the word of God.
Reference
Subhanallah …….quran is a blessing for mankind….
Subhan Allah. 1400 years old book in this world being read n followed is the quran. Even a few hundred years old books are no more followed taught or read.
This is a miracle itself.
How about sense of smell and taste and touch, all are alive while sleeping, if you don’t believe, check when your spouse will fart after eating indian curry