Daytime alertness and sleepiness as different faces of insomnia: An exploratory study

Insomnia has been traditionally associated with overactivation/hyperarousal in several domains of functioning. Daytime sleepiness, though a somehow expected phenomenon, has not been clearly demonstrated in most insomnia patients. In this study, we investigated whether a subgroup of self-reported insomnia sufferers with daytime sleepiness, and another subgroup with high levels of alertness/arousal, could be identified. From a previous large database comprising higher education students (n = 2,029), there were selected individuals aged 18-30 years who were full-time students and self-reported themselves as suffering from insomnia. Afterwards, three "insomnia" subgroups (n = 476) were created: 1) "Only Insomnia-Daytime Sleep Propensity"; 2) "Only Insomnia-Daytime Alertness"; and 3) "Neither Criterion". Data showed that in some important domains there are differences between self-reported insomnia individuals. Specifically, "Only Insomnia-Daytime Alertness" group displayed higher insomnia severity, sleep effort and distress about their sleep difficulties compared to "Only Insomnia-Daytime Sleep Propensity" group. Overall, the group which did not exhibit "Neither Criterion" presented significantly less daytime dysfunction, sleep and psychological symptomatology compared to the remaining groups. It seems plausible that arousal and daytime sleepiness may characterize disparate groups of insomnia sufferers. However, more systematic research is needed, mainly relying on objective and neurophysiological measures.