In patients with idiopathic hypersomnia, polysomnography typically shows short sleep latency, increased mean slow wave sleep, and a high mean sleep efficiency. "Latency to REM sleep and percentages of light sleep and REM sleep were normal, compared with normal ranges."[26] Despite this, one study has found increased sleep fragmentation in patients with idiopathic hypersomnia without long sleep time, suggesting multiple possible presentations.[27]