Caffeine increases tear volume depending on polymorphisms within the adenosine A2a receptor gene and cytochrome P450 1A2.
The primary aim of the present study was to examine the effect of caffeine on tear volume. The secondary aim was to investigate the relation between caffeine-induced changes in tear volume and polymorphisms in ADORA2A and CYP1A2.
Double-masked, placebo-controlled, crossover study.
Seventy-eight healthy volunteers were recruited for the study.
Subjects participated in 2 sessions in which they received capsules containing either placebo or caffeine. The caffeine capsules were given to the subjects to keep the caffeine volume per body weight within 5 to 7 mg/kg. After caffeine intake, tear meniscus height (TMH) was measured. Subjects provided a blood sample for genotyping.
MAIN OUTCOME MEASURES
Tear meniscus height, single nucleotide polymorphism.
The tear volume increased after caffeine consumption. The net increase in TMH was 0.08 mm (95% confidence interval, 0.05-0.10) greater when participants were given caffeine than when given placebo (P<0.0001). In ADORA2A, the difference in the net increase in TMH for participants who were heterozygous at rs5751876 and rs2298383 was 0.07 mm (P = 0.001) and who were minor homozygous was 0.08 mm (P = 0.007). In CYP1A2, the net increase in TMH for participants who were minor homozygous at rs2472304 was lower than for those who were major homozygous; the difference was 0.06 mm (P = 0.039).
Caffeine intake increases tear volume and polymorphisms within ADORA2A, and CYP1A2 is associated with the tear increase after caffeine intake. Genetic polymorphisms had a significant effect on tear meniscus that was of limited clinical significance.
Department of Ophthalmology, University of Tokyo School of Medicine, Tokyo, Japan. firstname.lastname@example.org
SourceOphthalmology 119:5 2012 May pg 972-8
Cytochrome P-450 CYP1A2
Polymerase Chain Reaction
Polymorphism, Single Nucleotide
Receptor, Adenosine A2A
Pub Type(s)Journal Article
Randomized Controlled Trial