Self-reported sleep and cognition: An examination of competing functional models
There are contrasting models that attempt to explain the mechanisms by which sleep impacts on cognition. One model suggests that there is a direct effect of sleep on memory and executive functioning. An opposing model suggests that sleep impacts on cognition indirectly – via sleepiness and lapses in attention. This study investigated the impact of sleep on cognition using self-report data from 205 participants. Overnight sleep duration/efficiency was assessed using the Sleep Efficiency factor of the PSQI to provide a measure of quantitative sleep. Daytime consequences of poor sleep, reflecting low arousal levels, were assessed using the PSQI Daily Disturbances factor and sleepiness on the Epworth Sleepiness Scale. Contrasting hypotheses were: (i) Poorer sleep duration/efficiency would directly predict poorer memory and executive functioning; and (ii) Lower daytime arousal would predict attention deficits, which would predict poorer memory and executive functioning. Regression analyses revealed support for an indirect effect of sleep on cognition, as attention largely explained the association. Results provide evidence of the critical role of low arousal on cognition. Importantly, the impact of Sleep Efficiency on cognition was accounted for by depression. Objective studies are needed to extend these findings, taking into account the role of attention and depression.