Associations between Quantitative Sleep Analysis and Cognitive Functions in Healthy Adults

Abstract

ABSTRACT Background: We investigated the role of sleep structure and sleep spindles on cognitive functions in healthy adults. Materials and Methods: Our study included 41 participants aged 18–65 years who had no other medical/sleep disorders. All participants underwent full-night polysomnography (PSG). The Standardized Mini-Mental Examination (SMME), Clock Drawing Test (CDT), forward and backward Digit Span Test (DST), Stroop test, and Beck Depression Inventory (BDI) were performed on all participants. Results: The study comprised 12 (29.2%) women and 29 (70.8%) men whose mean age was 47.0 ± 12.2 years. The mean forward DST score was significantly better in men than in women (P = 0.025). As age increased, the number of incorrect answers in the Stroop test (P = 0.016) increased. Of PSG data, a shorter duration of superficial sleep was associated with better scores in forward (t = −2.219; P = 0.040) and backward DST (t = −2.463; P = 0.024). Sleep spindle analysis showed that men had a significantly lower density compared with women (P = 0.046). A trend for a negative correlation was observed between increased sleep spindle density and lower Stroop test scores (t = −0.442; P = 0.051). The SMME, CDT, and BDI showed no significant associations with sleep structure. Decreased duration of sleep spindles significantly correlated with higher scores in forward (t = −0.480; P = 0.032) and backward DST (t = −0.489; P = 0.025). Conclusion: Our study showed that men had better functioning in attention, although they had a lesser amount of sleep spindles than women. This finding may be explained by socioenvironmental differences between the sexes. Sleep spindle characteristics, such as density and duration, are possibly associated with cognitive functions.