In responding to complex cognitive tasks, the insomnia group had slower and more variable response latencies, produced fewer correct responses, and had more errors than normal sleepers.
Individuals’ level of daytime sleepiness has impact on their ability to perform simple daytime cognitive tasks, while the presence of insomnia resulted in greater performance deficits on more complex tasks, according to findings from a cross-sectional study.
The study, led by Jack D. Edinger, PhD, insomnia specialist, National Jewish Health, included 35 patients with insomnia and 54 normal sleepers (NS) who underwent 2 nights of home-based polysomnography (PSG) followed by daytime testing with a 4-trial Multiple Sleep Latency Test (MSLT). The first nap commenced 2 to 3 hours after participants woke up from their second night of PSG monitoring, with each subsequent nap occurring at 2-hour intervals. Before each nap, patients completed a computer-administered batter of reaction time tests, including Rapid Visual Information Processing (RVP), Choice reaction time (CRT), Attention switching task (AST), Big/little circle (BLC), and Spatial working memory (SWM).
Twenty-five patients in the insomnia group and 24 in the NS group were classified as “alert,” defined as a MSLT mean latency of at least 8 minutes, whereas the remaining 10 in the insomnia group and 30 in the NS fell in the “sleepy” category of having MSLT mean latency of 8 minutes or less. Investigators conducted a 2 (insomnia vs NS) x 2 (alert vs sleepy) x 9 (measures) multivariate analysis of variance using the group of measures derived from the simple performance tests, and a second 2 (insomnia vs NS) x 2 (alert vs sleepy) by 18 (measures) such analysis with the group of measures derived from the more complex performance tests.
Results of this analysis of the simple performance task measures showed a significant main effect that correlated with alertness level (F[1,84] = 8.52; P = .0045). The data also showed that the participants classified as sleepy had significantly longer average response latencies on the CRT, greater response latency variability on both the simple reaction time and CRT, and fewer correct responses and more incorrect responses on CRT than those classified as alert.
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Based on those findings, investigators concluded that performance on the simple tasks was dictated by level of daytime sleepiness and not by the presence vs absence of insomnia. In contrast, the second multivariate analysis of complex reaction time test measures indicated a significant overall effect (F[1,84] = 6.62; P = .012) for insomnia vs NS patients. There was also a significant participant type by measure interaction (F[17,1428] = 6.62; P = .012).
On complex tasks, longer mean and more variable response latencies, as well as fewer correct responses on the AST were observed for those with insomnia compared to the NS group. Performance on the more complex tasks was dictated by presence vs absence of an insomnia disorder and not by participants’ level of daytime alertness because there was a greater error proneness within the insomnia group that was reflected by performances on AST and SWM test.
"Additional studies with a larger range of daytime tests as well as clinical trials that target the deficits noted would appear useful,” the study authors wrote.