K-complex morphological features in male obstructive sleep apnea-hypopnea syndrome patients.

This study characterized the differences in K-complex (KC) morphology features between obstructive sleep apnea-hypopnea syndrome (OSAHS) patients and healthy controls and analyzed the effect of respiratory events on KC morphology. We enrolled 42 male subjects (21 OSAHS patients and 21 age-matched healthy controls) who underwent overnight polysomnography. KCs in stage N2 were manually identified. We found that KCs in healthy controls had larger negative and whole amplitudes, longer durations, and smoother positive waves than OSAHS patients but smaller positive amplitudes. Most features showed highly significant differences after Bonferroni correction (p<0.001/3). After separating out the KCs associated with respiratory events in OSAHS patients, the differences between the groups remained but were relatively smaller. In OSAHS patients, compared with the spontaneous KCs not evoked by obvious factors, the KCs occurring after respiratory events had larger amplitudes, steeper slopes, larger negative wave amplitude and duration ratios. KCs occurring during respiratory events showed lower amplitudes and shorter durations. These results may reveal the impact of respiratory events on sleep and brain function.