Poor daytime functioning is a frequent complaint of those suffering from insomnia, said lead author Dr. Devon Hansen, a researcher in the Washington State University (WSU) Sleep and Performance Research Center and an assistant professor in the Elson S. Floyd College of Medicine.
A new study finds that people with sleep-onset insomnia who stay up all night perform up to twice as poorly on a reaction time test as healthy normal sleepers.
However, some research has shown that an insomniac’s daytime cognitive performance is not significantly degraded, seemingly suggesting that it is a perceived issue that does not actually reflect a real impairment.
The new findings reveal that this impairment is indeed very real but may be hidden during the normal day, only to be exposed after pulling an all-nighter.
For the study, the researchers observed 14 participants, half of whom struggled with chronic sleep-onset insomnia; defined as the inability to fall asleep within 30 minutes for at least three nights a week for more than three months.
The other half were healthy normal sleepers who served as controls. The two groups of participants were matched in age, with all participants aged between 22 and 40 and an average age of 29 for both groups.
Participants spent a total of five days and four nights in the sleep laboratory. They were allowed to sleep normally the first two nights. They were kept awake the next night and following day — totaling 38 hours of total sleep deprivation — followed by a night of recovery sleep.
During their time awake, participants completed a series of performance tasks every three hours. This included a widely used alertness test known as the psychomotor vigilance test (PVT), which measures participants’ response times to visual stimuli that appear on a screen at random intervals.
The researchers analyzed PVT data for lapses of attention (i.e., slow reaction times) and false starts (i.e., responses that occur before the stimulus appears), comparing the findings between the two groups both before and during sleep deprivation.
Before sleep deprivation, the insomnia group’s performance on the PVT looked very similar to that of the control group. However, as soon as sleep deprivation started the researchers began to see a dramatic increase in lapses of attention and false starts in the insomnia group. At one point during the night, their performance was twice as bad as that of the healthy normal sleepers.
The finding caught the WSU researchers by surprise.
“There has been a theory about what perpetuates insomnia that focuses on hyperarousal, an activation in their system that keeps those with insomnia from being able to wind down when they go to bed,” Hansen said.
“We thought that this hyperarousal would protect them to some extent and had hypothesized that their performance after a night of total sleep deprivation would be better than normal healthy sleepers. Instead, we found the exact opposite.”
Hansen, who previously worked as a therapist in a sleep clinic, said the study adds credibility to insomnia patients’ experiences. She also said it serves as a warning to poor sleepers that they should try to maintain a regular sleep schedule and avoid pushing their limits by staying up all night.
“Our study suggests that even with a few hours of sleep deprivation — which people routinely experience for work or family reasons — those with sleep-onset insomnia may be much more impaired than those who normally sleep well at night,” Hansen said.
“This may increase their risk of errors and accidents whenever time-sensitive performance is required, such as while driving or when focused on a safety-critical task.”
Hansen cautioned that since their study looked specifically at individuals with sleep-onset insomnia, their findings may not hold up in other insomnia subtypes, such as sleep-maintenance insomnia, characterized by difficulty staying asleep; and terminal insomnia. which involves early-morning awakenings. She plans to repeat the study in those groups to find out.
