Effects of mental workload and caffeine on catecholamines and blood pressure compared to performance variations

Caffeine is characterised as a central nervous system stimulant, also affecting metabolic and cardiovascular functions. A number of studies have demonstrated an effect of caffeine on the excretion of catecholamines and their metabolites. Urinary epinephrine and norepinephrine have been shown to increase after caffeine administration. Similar trends were observed in our study in adrenaline (ADR) and noradrenaline (NORADR) levels and additionally a dose dependant effect of caffeine. The effect of caffeine on cognitive performance, blood pressure, and catecholamines was tested under resting conditions and under mental workload. Each subject performed the test after oral administration of 1 cup and then 3 cups of coffee. Root mean square error (RMSE) for the tracking task was continuously monitored. Blood pressure was also recorded before and after each stage of the experiment. Catecholamines were collected and measured for three different conditions as: at rest, after mental stress alone, after one dose of caffeine under stress, and after triple dose of caffeine under stress. Comparison of the performance of each stage with the resting conditions revealed statistically significant differences between group of smokers/coffee drinkers compared with the other two groups of non-coffee drinkers/non-smokers and non-smokers/coffee drinkers. There was no statistically significant difference between the last two groups. There was an increase of urine adrenaline with 1 cup of coffee and statistically significant increase of urine noradrenaline. Both catecholamines were significantly increased with triple dose of caffeine. Mental workload increased catecholamines. There was a dose dependant effect of caffeine on catecholamines. (C) 2003 Elsevier Science (USA). All rights reserved.