Sleep-like Slow Waves During Wakefulness Mediate Attention and Vigilance Difficulties in Adult Attention-Deficit/Hyperactivity Disorder

Attention-Deficit/Hyperactivity Disorder (ADHD) is characterised by behavioural variability and heightened inattention associated with increased mind wandering (MW) and mind blanking (MB). Individuals with ADHD frequently experience sleep disorders and excessive daytime sleepiness, suggesting interactions between attention and arousal systems. Research examining brain activity using electroencephalography (EEG) has demonstrated that sleep-like slow waves (SW) during wakefulness are linked to inattention in neurotypical individuals following sleep deprivation, yet their role in ADHD remains unclear. This study investigated whether individuals with ADHD present with altered waking SW distribution compared to neurotypical controls and whether SW explain attentional difficulties in ADHD. Adults with ( n = 32) and without ADHD ( n = 31) completed a sustained attention task while EEG recorded brain activity. Mental state probes (on-task, MW, MB) were embedded within the task. Sleep-like SW reflect cortical slowing and were detected from EEG activity. Omission/commission errors, reaction time (RT), RT variability, mental state reports and subjective sleepiness were analysed. Mediation analysis examined whether SW density explained ADHD-related performance differences. Individuals with ADHD exhibited more commission errors, MW and MB, more theta oscillations over fronto-temporal electrodes and higher SW density (SW/min) over parieto-temporal electrodes. Increased SW density correlated with higher omission errors, slower RTs, greater RT variability, and elevated sleepiness ratings. On-task reports were negatively correlated with SW density. Mediation analysis revealed that SW density significantly accounted for ADHD-related attentional difficulties. Wake SW may explain attentional difficulties in ADHD, providing a potential mechanistic link between sleep disturbances and attentional fluctuations. Significance Statement We investigated whether slow waves during wakefulness could explain attentional difficulties in ADHD by comparing neurotypical adults and medication-withdrawn adults with ADHD during a sustained attention task with embedded mental state probes. Using electroencephalography, we quantified slow-wave activity and examined its relationship with objective performance measures and subjective reports of mind wandering and blanking. The ADHD group exhibited significantly higher slow wave activity which correlated with increased objective and subjective attentional lapses. Importantly, mediation analysis revealed that slow wave density accounted for performance differences between groups, suggesting that wake slow waves represent a neurophysiological mechanism underlying attentional difficulties in ADHD. These findings bridge sleep and attention research in ADHD, offering new insights into ADHD’s heterogeneous nature and potential intervention targets.