Is Having Had a Cup of Coffee a Methodological Issue in Routine Sphygmomanometry?

Background: In view of the impact of hypertension on public health, the objective of this study was to determine whether having had a cup of coffee in an everyday life setting raises blood pressure significant enough to make it a methodological issue in routine sphygmomanometry.
Methods: Healthy normotensive volunteers from a private university in Malaysia were recruited. After an overnight fast, seated systolic and diastolic blood pressures (SBP and DBP) of habitual coffee drinkers (n=16) were measured (Omron HEM 7080 automated monitor) in the laboratory 15 min. before and every 15 min. up to 90 min. after drinking strong coffee. This was repeated on non-habitual drinkers (n=16) who also underwent a control study (decaffeinated coffee). To see whether the laboratory findings could be extrapolated to everyday life setting, the pre-coffee BP and 30 min.- and 60 min.- post-coffee BPs were measured on habitual coffee drinkers (n=18) who consumed self-prepared coffee and who carried on with routine office work between BP measurements taken in a nearby room.
Results: In the laboratory setting, coffee significantly increased SBP and DBP at all time-points in non-habitual drinkers (e.g.11.38+/- 8.2 and 10.75+/-5.7 mm Hg at 75 min; P<0.01, repeated measures ANOVA and Dunnett's test); in habitual drinkers, SBP only was increased (7.23+/-4.7 at 90 min; P<0.05). In the office setting, smaller but significant DBP elevations (3.72+/-5.1 at 60 min; P<0.05) were observed.
Conclusion: The results indicate that having had a cup of coffee could be a methodological issue in routine sphygmomanometry, particularly with non-habitual coffee drinkers consuming strong coffee. However, caution should be exercised in drawing conclusions because of the small sample size.