Sleep spindles and general cognitive ability – A meta-analysis

Abstract

The scientific discussion of sleep spindles now routinely mentions the association between these oscillations and cognitive ability. Numerous studies have been published on the topic with various methodologies and highly divergent results. In this meta-analysis of the relevant literature (total k = 22 articles, total N = 953 subjects), it is concluded that there is evidence for a modest positive association between cognitive ability and slow (r = .113) and fast (r = .183) spindle amplitudes and also some evidence for an association between cognitive ability and slow spindle duration (r = .087) but none for associations with other parameters. Evidence for publication bias was found in case of fast spindle amplitude and density, but the correlation between cognitive ability and amplitude was robust to this effect. Studies with more females reported weaker associations with slow spindle duration, but this effect was driven by a single study with an all-male sample, and no other effect size was significantly moderated by age or sex. Most studies were conducted in small data sets and did not exhaustively report all measured associations. It is recommended that future studies having access to both sleep spindle and intelligence measures report their associations, regardless of their nature, that data sets be pooled across research groups for more statistical power, and that at least a basic agreement of spindle detection and classification criteria be reached in the research community.