... during sleep in 400 patients with sleep apnea syndrome. Am J Cardiol, 1983;52:490-494. 11. Gillis AM, Stoohs R, Guilleminault C. Changes in the QT in- terval during obstructive sleep apnea. Sleep, ... hypopnea. Individuals with an apnea hypopnea index (AHI) >5 were diagnosed as OSAS and included in the study. Determining of Arousals An arousal was defined as an increase in EEG and/or EMG ... de-fining the current sleep stage. An arousal was scored; during NREM sleep consisting of an abrupt EEG fre-quency shift (eg, alpha, theta, or frequencies >16 Hz, but not spindles) lasting...