Physiological Sleep Features Associated With Dimensions of Daily Dysfunction in Insomnia

Daily dysfunction is a key criterion of insomnia, but its underlying structure and relationship with objective sleep physiology remain unclear. This study aimed to identify the dimensions of subjective daily dysfunction using exploratory factor analysis (EFA) in individuals with insomnia and to examine its association with polysomnography (PSG) macroarchitecture, electroencephalographic (EEG) spectral power and odds ratio product (ORP)-based sleep depth in individuals with and without insomnia. We hypothesized that more severe daily dysfunction would be associated with poorer sleep continuity, higher high-frequency EEG activity and lighter sleep depth. The final sample included 859 adults (50.1% female; mean age 44.2 ± 14.1 years) in the Sleep Apnea Global Interdisciplinary Consortium (SAGIC) without obstructive sleep apnea (OSA) or shift work, including 368 with insomnia. EFA supported a single factor underlying the nine daily dysfunction items, which were combined into a total score. In univariate linear regression analyses adjusted for age, sex and site, higher beta-1 power and several ORP measures were nominally associated with more severe daily dysfunction, but none of them survived correction for multiple comparisons. No significant predictor-by-group interactions were observed. Across three levels of sleep physiology-PSG macroarchitecture, spectral power, and continuous sleep depth-no sleep measure was associated with daily dysfunction after correction for multiple comparisons. PSG macroarchitecture and sleep EEG-derived measures may not fully capture daily dysfunction. Future studies could examine whether within-night sleep dynamics are more informative than whole-night averages.