How are CYP1A2 and Schlaf related?

CYP1A2 is the primary enzyme responsible for caffeine metabolism. The rs762551 variant (C vs A allele) determines whether an individual is a slow or fast caffeine metabolizer. Slow metabolizers (C allele) maintain higher caffeine levels for longer, which can delay sleep onset, reduce sleep quality, and shorten deep sleep phases – especially if caffeine is consumed in the afternoon. There is no strong evidence for a direct effect of CYP1A2 on sleep independent of caffeine. The evidence is based on pharmacokinetic studies and observational data, not large randomized trials. The effect is moderate and varies between individuals. For those with sleep issues, reducing caffeine intake – particularly if they are slow metabolizers – may be beneficial. A genetic test can provide a clue but does not replace clinical sleep assessment.