Overview of Sleep Problems Sleep is essential to physical and emotional health. Adequate sleep may also play a role in helping the body recover from illness and injury. Sleep Apnea Sleep apnea is a breathing disorder in which a person experiences brief interruptions of breathing during sleep. Insomnia Insomnia, the term for having trouble sleeping at night, is one of the most common sleep complaints. About one in three adults has bouts of insomnia that last a few days at a time.