Figure 1 Hourly slow-wave energy and slow-wave activity during baseline for the DQB1*0602 groups

Mean (±SEM) hourly slow-wave energy (SWE) and slow-wave activity (SWA) derived from the C3 (A, B), Fz (C, D), or O2 (E, F) channels during baseline for DQB1*0602-negative subjects (open circles) and DQB1*0602-positive subjects (closed circles). SWE derived from C3 was lower in DQB1*0602-positive subjects (denoted by **, p < 0.05); SWA derived from C3 and SWE and SWA derived from the Fz channel showed similar trends. As expected, SWE and SWA showed a typical pattern of dissipation across the baseline night in all 3 channels for both groups (denoted by *, p < 0.05); moreover, DQB1*0602-positive subjects demonstrated sharper declines in sleep pressure derived from the O2 channel during the first few hours of the night than DQB1*0602-negative subjects (denoted by †, p < 0.05). In some records, EEG signal quality was insufficient or contained too much artifact for reliable power spectral analysis. Thus, the final sample sizes were as follows: for C3, DQB1*0602-negative (n = 68) and -positive (n = 24) subjects; for Fz, DQB1*0602-negative (n = 70) and -positive (n = 28) subjects; for O2, DQB1*0602-negative (n = 74) and -positive (n = 27) subjects.