Exploring the Relationship Between Caffeine Consumption, Caffeine Metabolism, and Sleep Behaviours: A Mendelian Randomisation Study.

Summary

This Mendelian randomisation study used genetic proxies for caffeine consumption and metabolism across multiple large cohorts (including UK Biobank) to explore causal relationships with sleep behaviours. Higher caffeine consumption causally decreased daytime sleepiness, whilst faster caffeine metabolism reduced daytime napping likelihood; however, no causal relationship was detected for sleep duration or insomnia. The findings suggest caffeine primarily affects daytime alertness rather than nighttime sleep characteristics, though the authors acknowledge weak instruments for caffeine metabolism and significant heterogeneity as limitations.

Regional applicability

The study is United Kingdom–based, drawing substantially from UK Biobank data, and findings are directly applicable to UK populations. The use of genetic instruments and large cohort data provides robust evidence for UK clinical and public health contexts regarding caffeine's effects on sleep and daytime alertness.

Key measures

Genetic variants associated with caffeine consumption, caffeine metabolism, chronotype, daytime napping, daytime sleepiness, difficulty getting up in morning, insomnia, and sleep duration; univariable and multivariable Mendelian randomisation effect estimates (β coefficients with 95% confidence intervals)

Outcomes reported

The study investigated causal relationships between caffeine consumption, caffeine metabolism, and multiple sleep behaviours (daytime sleepiness, napping, chronotype, insomnia, sleep duration) using Mendelian randomisation. Key findings included effects on daytime sleepiness and napping, but not on sleep duration or insomnia.

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