DAYTIME ALERTNESS IN PATIENTS WITH PRIMARY INSOMNIA

Objective: In the absence of clear distinctions in alertness between p atients with primary insomnia and normal subjects, the goal of this st udy was to identify psychometric and electrophysiological measures tha t would distinguish these two groups. Method: The daytime alertness of 20 primary insomnia patients and 20 normal subjects was investigated through their scores on a 26-item hyperarousal scale and measurement o f auditory evoked potentials and alpha and nonalpha band EEG activity. Statistical analysis of the data included correlation of the hyperaro usal scores and the electrophysiological measures. Results: The hypera rousal scores showed clearly higher daytime alertness in the insomnia patients compared with the normal subjects. In addition, during wakefu lness, the insomnia patients showed greater amplitudes of P1N1, a dura ble, intrinsic, late (cortical) component of the auditory evoked poten tial, as well as greater EEG activity across the frequency spectrum. T he hyperarousal scores correlated positively with the amplitude of P1N 1 at each of three sound intensities. Conclusion: To the authors' know ledge, this is the first study to offer evidence that patients with pr imary insomnia have objectively definable features during wakefulness that clearly distinguish them from normal subjects. The measurement of hyperarousal might be used to refine descriptions of insomnia populat ions in experimental studies.