What this means

ADORA2A codes for the adenosine A2A receptor — the receptor caffeine blocks to keep you alert. A common variant (rs5751876) affects how strongly caffeine disrupts sleep architecture and how anxious people feel after caffeine intake. TT carriers tend to report worse sleep after evening caffeine, and to feel more jittery after the same dose of coffee. The effect is consistent across studies but small in absolute terms — for most people, timing and dose matter more than this SNP.

Caffeine wakes you up by blocking a specific receptor in your brain called the adenosine A2A receptor — that receptor is what normally makes you feel sleepy as the day goes on. A common DNA change in this receptor affects how badly caffeine wrecks your sleep, and how jittery the same cup of coffee makes you feel. People with two copies of the sensitive version tend to lose more sleep from evening caffeine. The effect is real and consistent across studies, but small — timing and dose still matter more.

Caveats

• Effect is well-replicated but modest. Sleep hygiene matters more.
• Caffeine metabolism (CYP1A2) and this receptor variant interact — both contribute.
• Tolerance to caffeine still builds with regular use.
• Individual sleep responses to caffeine vary widely even within the same genotype.

References

• Rétey et al. — A genetic variation in the adenosine A2A receptor gene (ADORA2A) contributes to individual sensitivity to caffeine effects on sleep (Clinical Pharmacology & Therapeutics, 2007)
• Byrne et al. — A genome-wide association study of caffeine-related sleep disturbance (Sleep, 2012)