what causes people to wake up in the night
Sleep apnea is another sleep disorder linked to insomnia. With sleep apnea, a person's airway becomes partially or completely obstructed during sleep, leading to pauses in breathing and a drop in oxygen levels. This causes a person to wake up briefly but repeatedly throughout the night. People with sleep apnea sometimes report experiencing insomnia.
Excessive daytime sleepiness is reported nearly two times higher by individuals with nocturnal awakenings than by people who sleep through the night. Sleep research conducted already in the 1990s showed that such waking up during the night may be a natural sleep pattern, rather than a form of insomnia.