Purpose
To examine the effect of caffeine on retinal vessel diameters in the Inter99 Study.
Methods
The Inter99 Study comprised a population‐based age‐and sex‐stratified sample of 13,016 residents of a suburban section of Greater Copenhagen, Denmark. From 6784 participants aged 30‐60 years who volunteered to participate in the main study, a subgroup of 970 participated in the eye study. Vessel diameters were measured using a semi‐automatic computer program. Exclusion of participants without images of acceptable quality (n71) left 899 participants for analysis. Coffee and tea intake assessed using a food frequency questionnaire (FFQ) ranged from 0 to 35 cups. One cup of tea or coffee was assumed to contain 100 mg of caffeine.
Results
Of 899 eligible participants, 861 were daily coffee or tea drinkers, a mean of 5 cups per day. Thirty eight did not drink tea or coffee. The central retinal artery diameter was 214 μm in participants who did not drink tea or coffee and 209 μm in participants who drank tea or coffee (B = ‐5.7 CI 95%: ‐10.5 to ‐1.0, p = 0.019, adjusted for age, gender, systolic blood pressure, HDL cholesterol, BMI, diabetes mellitus status and smoking status). The central retinal vein diameter was 261 μm in participants who did not drink tea or coffee and 252 μm in participants who drank tea or coffee (B = ‐8.6 CI 95%: ‐15.2 to ‐2.0, p = 0.011, adjusted for age, gender, systolic blood pressure, HDL cholesterol, BMI, diabetes mellitus status and smoking status).
Conclusions
This cross‐sectional study found that participants who drank tea or coffee on a daily basis had narrower central retinal arteries and veins than participants who did not drink tea or coffee. This is consistent with previous observations that caffeine induces cerebral vasoconstriction by antagonizing adenosine receptors.
