Daytime Performance in Insomnia Patients

Patients suffering from Nonorganic Insomnia (NI) are burdened by significant subjective daytime impairments which contribute to the reduction of quality of life for the patients and lead to greater healthcare utilization and increased indirect costs. Besides being central to diagnosis, operationalized criteria for daytime symptoms are lacking and data remain heterogeneous, especially regarding objectively measurable deficits. This study examines daytime performance in 329 NI patients through neuropsychological testing as well as self-report questionnaires, and correlates the results with polysomnographic data. In the main analysis, neuropsychological data, normalized for age and health status, displayed no impairment of vigilance or alertness-contrary to what is often assumed for NI and what would typically be expected in cases of sleepiness. For secondary analyses, neuropsychological data was then correlated with self-report and polysomnographic measures, and comparisons between NI patients with and without comorbidities were conducted. NI patients displayed a positive correlation of performance with nocturnal arousal markers, predominantly during REM sleep and a slightly diminished capability to increase focus in the phasic compared to tonic alertness paradigm. In summary, the current study in a well characterized large sample of NI patients with state-of-the-art measures of the most sensitive markers for sleep related daytime impairment found no evidence for diminished general vigilance or alertness due to sleep loss. The results help to understand conflicting evidence on neurocognitive deficits in insomnia by distinguishing between alertness or vigilance deficits and subtle changes in neurocognitive processing that might be better interpreted in line with underlying hyperarousal and anxiety.