['Respiratory cycle-related EEG changes (RCREC) have been demonstrated during sleep by digital analysis and hypothesized to represent subtle inspiratory microarousals that may help to explain daytime sleepiness in patients with sleep-disordered breathing. We therefore examined for the first time associations between RCREC and esophageal pressure swings (deltaPes) that reflect work of breathing.', 'Retrospective analysis.', 'Academic sleep laboratory.', 'Forty adults referred for suspected sleep disordered breathing.', 'Polysomnography with esophageal pressure monitoring and automatic computation of deltaPes using a novel algorithm.', 'Computed deltaPes for nearly all respiratory cycles during sleep correlated well with visual scoring of selected respiratory cycle samples (Spearman rho = 0.86, P < 0.0001). The RCREC within the sigma EEG range (12.5-15.5 Hz) rather than that within other frequency ranges most often showed significant within-subject inverse correlations with deltaPes. In contrast, in between-subject comparisons, beta (15.5-30.5 Hz) and to a lesser extent theta (4.5-7.5 Hz) RCREC, rather than sigma RCREC, showed significant inverse associations with mean APes.'] Do respiratory cycle-related EEG changes during sleep reflect esophageal pressures?