Sleep duration and IQ: confusing data or confusing conceptions?

Sleep Med. 2010 Mar;11(3):289-94. doi: 10.1016/j.sleep.2009.09.007. Epub 2010 Feb 13.

Short sleep duration is associated with poor performance on IQ measures in healthy school-age children.

Gruber R, Laviolette R, Deluca P, Monson E, Cornish K, Carrier J.

Source

Douglas Mental Health University Institute and McGill University, Montreal, Quebec, Canada. reut.gruber@douglas.mcgill.ca

Abstract

OBJECTIVE:

To examine the associations between habitual sleep duration and intellectual functioning in healthy, well-rested, school-age children.

METHODS:

The study group consisted of 39 healthy children, aged 7-11 years old. Nightly actigraphic sleep recordings were taken for four consecutive nights to determine habitual week-night sleep duration in the home environment. Objective measures of cognitive functioning and sleepiness were used to measure daytime functioning.

RESULTS:

Longer habitual sleep duration in healthy school-age participants was associated with better performance on measures of perceptual reasoning and overall IQ, as measured by the WISC-IV, and on reported measures of competence and academic performance. No association between sleep duration and the studied behavioral measures was found.

CONCLUSIONS:

These findings support the hypothesis that sleep duration is differentially related to some components of cognitive functioning, even in the absence of evidence for sleep deprivation or attention deficits.

"Studies involving children and adults have identified a significant relationship between poor or insufficient sleep and decreased cognitive capacity (Beebe, 2011, Bell-McGinty et al., 2004, Busby and Pivik, 1983,Caldwell et al., 2005, Carskadon et al., 1981, Chee and Choo, 2004, Chee et al., 2006, Choo et al., 2005,Dewald et al., 2010, Fallone et al., 2001, Gozal and Kheirandish-Gozal, 2007, Gruber et al., 2010, Habeck et al., 2004, Lim et al., 2007, Mu et al., 2005a, Mu et al., 2005b, Nixon et al., 2008, Randazzo et al., 1998,Sadeh et al., 2003, Schabus et al., 2006, Touchette et al., 2007, Voderholzer et al., 2011 and Wilhelm et al., 2012)."

Review

The function of the sleep spindle: A physiological index of intelligence and a mechanism for sleep-dependent memory consolidation

• Stuart M. Fogel^a, , , , 
• Carlyle T. Smith^b, 

• ^a University of Montreal, Montreal, Quebec, Canada, H3W 1W5
• ^b Department of Psychology, Trent University, Peterborough, Ontario Canada, K9J 7B8

• http://dx.doi.org/10.1016/j.neubiorev.2010.12.003, How to Cite or Link Using DOI

• Permissions & Reprints

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Abstract

Until recently, the electrophysiological mechanisms involved in strengthening new memories into a more permanent form during sleep have been largely unknown. The sleep spindle is an event in the electroencephalogram (EEG) characterizing Stage 2 sleep. Sleep spindles may reflect, at the electrophysiological level, an ideal mechanism for inducing long-term synaptic changes in the neocortex. Recent evidence suggests the spindle is highly correlated with tests of intellectual ability (e.g.; IQ tests) and may serve as a physiological index of intelligence. Further, spindles increase in number and duration in sleep following new learning and are correlated with performance improvements. Spindle density and sigma (14–16 Hz) spectral power have been found to be positively correlated with performance following a daytime nap, and animal studies suggest the spindle is involved in a hippocampal–neocortical dialogue necessary for memory consolidation. The findings reviewed here collectively provide a compelling body of evidence that the function of the sleep spindle is related to intellectual ability and memory consolidation.