Narcolepsy, a condition where people fall asleep unexpectedly, affects roughly 1 in 2,000 people in the United States. In addition to the sleepiness, another symptom is cataplexy, episodes of partial or total loss of muscle control, often triggered by a strong emotion such as laughter. Narcolepsy affects roughly 1 in 2,000 people. So if you’re experiencing sleepiness, it’s probably not narcolepsy, but the condition can be serious for the 0.05 percent of the population affected by it. Learn more