rs2472297

rs2472297 is a common marker between CYP1A1 and CYP1A2. Each T copy is linked to less caffeine remaining in the blood and a higher caffeine-breakdown ratio, both pointing to slightly faster clearance. A multi-ancestry study estimated a 0.142-standard-deviation decrease in blood caffeine per T copy and about 0.48% of variation explained. The T version is common in European groups, less common in African, Hispanic, and South Asian groups, and nearly absent in East Asian groups. This marker cannot predict alertness, jitters, sleep effects, caffeine dose, or a cutoff time. Ensembl also lists a rare A version; genotypes containing A are not interpreted.