The technical term is "confusional arousal," and it means confusion and memory impairment after a particularly rough night of sleep. Usually, these episodes are linked to sleep deprivation, using tranquilizers or hypnotics before falling asleep, or waking up a few times during the night. Unlike that regular-old, extra-tired feeling, being sleep drunk means you're unresponsive and disoriented. In a milder episode, you might have difficulty getting dressed or keeping your balance.
This research, published in the journal Neurology, offers the first glimpse into the disorder. To assess the prevalence of sleep drunkenness, the investigators surveyed almost 16,000 people from 15 states by phone. The Sleep EVAL survey collected information about participants' sleep patterns, whether they had any other sleep disorders, and whether or not they took any medications. With this information, the researchers were able to diagnose how often participants experienced confusional arousals and the behaviors that potentially lead to them.
Their results were pretty astounding — 15% of the survey population said they'd had an episode of sleep drunkenness in the past year. And, more than half of these participants said they experience an episode once per week. The episodes tended to last for less than 15 minutes, but 37.6% of participants reported them lasting less than five minutes.
Past research was only able to estimate the prevalence of sleep drunkenness. One study suggested that 17% of children under 13 years old experienced this phenomenon, and that episode frequency decreases as we age. And, although you don't need to also be actually drunk in order to be sleep drunk, another study has suggested that drinking alcohol before bed could make confusional arousals more likely. So, the next time you have an extra-horrible hangover, more than one kind of drunkenness may be to blame.