Daytime alertness in subjective and objective insomnia: some preliminary findings.

Daytime performance and alertness were examined in two groups of patients with disorders of initiating and maintaining sleep (DIMS) and a control group of self-described good sleepers. Individuals complaining of disturbed sleep that was verified by polysomnographic indices (objective DIMS) and a group with complaints of disturbed sleep in the absence of objective findings (subjective DIMS) were compared with normal sleepers. Nocturnal polysomnographic recordings documented increased sleep latencies and decreased sleep efficiencies for the objective DIMS group and essentially normal sleep for the subjective DIMS group. However, the subjective DIMS group showed impaired daytime vigilance compared with both the objective DIMS and control groups. Additionally, the subjective DIMS group demonstrated an atypical daytime alertness and a tendency toward lowered arousal during vigilance task performance. Insomniacs without clear objective findings of disturbed sleep, therefore, showed decrements commonly seen following sleep loss or sleep disturbance, whereas insomniacs with evidence of disturbed nocturnal sleep did not differ from the control group in terms of waking function.