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Chronotype and cognitive function: Observational study and bidirectional Mendelian randomization.

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Later sleep times (chronotype) are not detrimental to cognitive function and may even be beneficial. This study offers reassurance to individuals with later chronotypes regarding their cognitive health.

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Area of Science:

  • Chronobiology
  • Cognitive Neuroscience
  • Genetics

Background:

  • Observational studies suggest a link between chronotype and cognitive function, but causality and directionality remain unclear.
  • Individuals with later chronotypes often worry about potential negative impacts on their cognitive abilities.

Purpose of the Study:

  • To investigate the causal relationship between chronotype and cognitive function.
  • To determine if later chronotype is associated with poorer cognitive performance.

Main Methods:

  • Utilized multivariable linear regression on 14,582 participants from the Guangzhou Biobank Cohort Study (GBCS).
  • Employed bidirectional Mendelian randomization (MR) using 207 single nucleotide polymorphisms (SNPs) for chronotype and 127 SNPs for cognitive function from large-scale genetic datasets (UK Biobank, 23andMe, COGENT).

Main Results:

  • Observationally, later chronotype in GBCS was linked to better cognitive function (MMSE and Delayed Word Recall Test scores).
  • Bidirectional MR indicated no causal effect of genetic predisposition to early chronotype on cognitive function.
  • Conversely, better cognitive function was associated with decreased odds of having an early chronotype.

Conclusions:

  • The findings are reassuring for individuals with later chronotypes, suggesting their habits are not detrimental to cognitive function.
  • The study suggests a potential reverse causation, where better cognitive function might influence chronotype rather than vice versa.