Can CYP1A2 rs762551 AC and ADORA2A rs5751876 TT increase vulnerability to caffeine-related sleep disruption?

Individual responses to caffeine depend on a balance between liver clearance rates and central nervous system receptor sensitivity.

Pharmacokinetic clearance

• Slower clearance rates: The CYP1A2 rs762551 AC genotype designates a slow or intermediate metabolizer. Because the CYP1A2 enzyme mediates up to 95% of caffeine clearance, AC carriers have reduced enzyme activity and a prolonged caffeine half-life of 4 to 6 hours, compared to 2 to 3 hours in AA fast metabolizers.
• Extended nighttime stimulation: Slower clearance maintains elevated plasma concentrations of caffeine late into the evening. This persistent circulation allows caffeine to continuously block adenosine signaling at bedtime, disrupting sleep architecture and delaying sleep onset.

Receptor-level pharmacodynamics

• Receptor blockade: Caffeine promotes wakefulness by acting as a competitive antagonist at adenosine A2A receptors, encoded by the ADORA2A gene.
• Genotype-specific sensitivity: The claim that the ADORA2A rs5751876 TT genotype directly causes sleep disruption is unsupported; clinical evidence shows that the C/C genotype is the primary variant linked to caffeine-induced insomnia and altered sleep EEGs.
• Anxiety-induced sleep delay: However, the TT genotype is a high-sensitivity variant associated with heightened caffeine-induced anxiety and emotional reactivity. This increased jitteriness can indirectly interfere with the ability to wind down and initiate sleep.

Bottom line

• Slower caffeine clearance from the CYP1A2 rs762551 AC genotype directly prolongs stimulant effects into the night to disrupt sleep. However, direct receptor-mediated sleep sensitivity is driven by the ADORA2A rs5751876 C/C genotype, while the TT genotype instead increases susceptibility to caffeine-induced anxiety that can indirectly delay sleep.