Young poor sleepers mobilize extra effort in an easy memory task: evidence from cardiovascular measures

Insomniacs often complain of memory deficits, yet objective measures have not consistently corroborated their subjective impressions. A possible explanation for the partial gap between self-report and behavioral measures of memory impairment is that insomniacs recruit extra effort to compensate for the consequences of poor sleep. The present study investigated whether subjective insomnia severity would predict objective effort mobilization, as indexed by cardiovascular measures, in an easy memory task. Seventy-seven university students, mostly women, with a mean age of 22 years were asked to memorize four strings of four random letters in 5 min while cardiovascular measures were obtained. After taking an immediate recall test, participants completed the Insomnia Severity Index, the Multidimensional Fatigue Inventory, and a questionnaire on last night's sleep and today's fatigue. Finally, they were given a surprise delayed recall test. Analyses indicated that self-reported insomnia severity was associated with an increase in systolic blood pressure during the learning phase. Regarding memory performance, insomnia severity was unrelated to immediate recall but related to a decrement in delayed recall. These findings reveal for the first time that subjective insomnia severity predicts objective effort mobilization in an easy memory task, suggesting that young poor sleepers recruit extra resources to cope with everyday cognitive challenges.