Abstract
Introduction Sleep-deprivation is increasing in prevalence and compensatory napping is becoming common practice. Little is known about the cognitive benefits derived from a nap in sleep-deprived individuals, or within the student population. Furthermore, few studies have investigated the cognitive benefits of napping using the incongruent Stroop test. This study aimed to investigate the effects of a nap-opportunity on cognitive function in individuals aged 18–30.
Methods A randomised, crossover study was conducted. Participants were recruited from Imperial College London and were allocated to either control (no nap-opportunity) or intervention (20-minute nap-opportunity) groups.
The incongruent Stroop test was used to measure reaction time (RT) and percentage accuracy, which were used as markers of cognitive function. ΔRT and Δ percentage accuracy, between control and nap-opportunity groups were compared. Paired and unpaired t-tests were used for the analysis of RT. Wilcoxon signed-rank and Mann-Whitney-U tests were used to test the percentage accuracy. The study was approved by the Imperial College Medical Education Ethics Committee.
Results Participants (n=29) had a mean age of 20 (SD±1.4) years, 55% male. In those who were acutely sleep-deprived, the RT improved in the intervention group following a 20-minute nap-opportunity, compared to the control group (p=0.01; figure 1). Overall, no significant difference in Δ percentage accuracy was observed between the control and nap-opportunity groups (p=0.31).
Dot plot showing reaction times in incongruent Stroop test, measured before and after a 20 minute nap-opportunity in individuals who slept for <8hrs the night before the test (n=18) and =8hrs the night before the test (n=11). Data presented as mean ±95% CI. Paired t-test was used to compare reaction times before and after nap-opportunity. Unpaired t-tests were used to compare baselines and endpoints of the two groups. Significant change in reaction time was observed following nap-opportunity in individuals who slept<8 Hours before the test day (p=0.01275) *=P<0.05, **=P<0.01, ***=P<0.001
Conclusions The main finding of this study was that the sleep-deprived group derive greater benefit in cognitive function from a 20-minute nap-opportunity. Future studies could investigate the relationship between the amount of sleep-deprivation and the magnitude of benefit derived from a nap-opportunity. Moreover, the impact of napping in individuals who are chronically sleep-deprived should also be explored.
