Effects of Cognitive Arousal On Sleep Perception

By Dr. Gregg D. Jacobs

This study, conducted by K.Y. Tang and A.G. Harvey in England, was published in the January, 2004 issue of Sleep (27: 69-77). Prior studies have documented that insomniacs overestimate sleep onset latency and awake time after sleep onset and underestimate total sleep time. Additionally, several studies have shown that, when awakened from stage 2 sleep, insomniacs are more likely than good sleepers to report that they were not sleeping.

Although several researchers have proposed that excessive pre-sleep cognitive arousal may be the basis for these distorted sleep perceptions, no studies have tested this hypothesis. The purpose of this study was to examine the effect of presleep cognitive arousal on sleep perception.

The investigators tested the effects of presleep cognitive arousal on sleep by studying three groups of normal sleepers. The first group was told that they would give a talk to three people after taking a nap (anxious cognitive arousal). The second group was told that they would write an essay after a nap (neutral cognitive arousal), while a third group was simply told to take a nap (control). Subjects were then allowed to take a one hour nap while their sleep was recorded objectively.

After taking a one hour nap, the researchers immediately asked each group of subjects how long they thought it took them to fall asleep and how long they slept. The researchers found that the anxious cognitive arousal subjects exhibited the greatest discrepancy between self-report and objective measures of sleep latency and total sleep time, followed by the neutral arousal group and then the control group.

These findings suggest that presleep cognitive arousal is a cause of distorted sleep perception; and, the more anxious the cognitive arousal, the greater the discrepancy between perceived and actual sleep. Although this study used normal sleepers, these results suggest that insomniacs' may overestimate sleep latency and underestimate total sleep time due to pre-sleep cognitive arousal. Additionally, the results suggest that reducing presleep anxiety and cognitive arousal will lead to more accurate perception of sleep.