| Disorder | Rate | Description | Effects |
|---|
| Insomnia | 1 in 10 adults; 1 in 4 older adults | Ongoing difficulty falling or staying asleep. | Chronic tiredness. Reliance on sleeping pills and alcohol, which reduce REM sleep and lead to tolerance—a state in which increasing doses are needed to produce an effect. |
| Narcolepsy | 1 in 2000 adults | Sudden attacks of overwhelming sleepiness. | Risk of falling asleep at a dangerous moment. Narcolepsy attacks usually last less than 5 minutes, but they can happen at the worst and most emotional times. Everyday activities, such as driving, require extra caution. |
| Sleep apnea | 1 in 20 adults | Stopping breathing repeatedly while sleeping. | Fatigue and depression (as a result of slow-wave sleep deprivation), and obesity (especially among men). |
| Sleepwalking/sleeptalking | 1–15 in 100 in the general population | Doing normal waking activities (sitting up, walking, speaking) during NREM-3 sleep. | Few serious concerns. People return to their beds on their own or with the help of a family member, rarely remembering their trip the next morning. |
| Night terrors | 1 in 100 adults; 1 in 30 children | Appearing terrified, talking nonsense, sitting up, or walking around during NREM-3 sleep; different from nightmares. | Doubling of a child’s heart and breathing rates during the attack. Luckily, children remember little or nothing of the fearful event the next day. As people age, night terrors become more and more rare. |