Impact of daytime sleepiness and insomnia on simple and complex cognitive task performances.

OBJECTIVE

To examine the individual and combined effects of daytime sleepiness and insomnia disorder (ID) on measures of cognitive functioning.

DESIGN AND

SETTING

This study was conducted at a medical center using a cross-sectional research design.

PARTICIPANTS

35 persons with ID (Mage = 40.6 years; 25 women) and 54 normal sleepers (NS; Mage = 31.5 years; 38 women).

METHODS AND MEASURES: Participants underwent two nights of home-based polysomnography (PSG) followed by daytime testing with a four-trial Multiple Sleep Latency Test (MSLT). Before each MSLT nap, they completed a computer-administered battery of reaction time tasks. Measures of response latencies and response accuracy were tabulated and used as dependent measures. The ID and NS groups were each subdivided into "alert" (eg, MSLT mean latency > 8 min) and "sleepy" (eg, MSLT mean latency ≤ 8 min) subgroups to identify hyperaroused persons with ID and allow for their comparisons with the other participant subgroups.

RESULTS

Multivariate analyses of variance showed a significant main effect for level of daytime sleepiness (F [1, 84] = 8.52, p = 0.0045) on simpler performance tasks and a significant main effect for presence vs. absence of ID (F [1,84] = 6.62, p = 0.012) on complex tasks. A lack of significant participant type x MSLT alertness level interactions in study analyses suggested those ID participants with presumed hyperaousal were not relatively more impaired than the other participant subgroups.

CONCLUSIONS

Daytime performance deficits on simple tasks seem most dependent on individuals' levels of daytime sleepiness, whereas performance deficits on more complex tasks appears related to the presence of ID. Therefore, it seems best to use complex performance measures both to document cognitive deficits among those with ID and to determine if insomnia treatments reduce such impairments.

TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02290405.