PHARMACOKINETIC AND PHARMACODYNAMIC RESPONSES TO CAFFEINE IN POOR ANDNORMAL SLEEPERS

Pharmacokinetic and pharmacodynamic responses to caffeine (2.5 mg/kg) were compared between ten healthy self-rated poor sleepers and ten nor mal sleepers. Sleep pattern assessed by the Pittsburgh Sleep Quality I ndex (PSQI). There was no significant difference in mean estimated dai ly caffeine consumption between the groups. The poor sleepers had sign ificantly higher scores for neuroticism on the Eysenck Personality Que stionnaire (EPQ) and anxiety on the Hospital Anxiety Depression (HAD) scale, compared with normal sleepers. Caffeine pharmacokinetics were a ssessed by measurement of saliva caffeine concentrations. Poor sleeper s showed significantly greater variability in caffeine C-max, clearanc e and half-life, compared to normal sleepers. Pharmacodynamic measures included heart rate, blood pressure, visual analogue scales for conce ntration, vigilance and relaxation, psychomotor performance [Digit Sym bol Substitution Test (DSST) and tapping rate (TR)] and EEG activity [ Contingent negative variation (CNV), auditory evoked potential and pow er spectral analysis]. Prior to caffeine administration, poor sleepers compared to normal sleepers had faster heart rates, lower ratings for concentration and relaxation, poorer performance on the DSST greater CNV magnitude, faster peak alpha frequency and lower delta, theta and beta power. These differences persisted after caffeine ingestion and o verall differences between the groups on these measures were significa nt (P < 0.01-0.001). Post-dose, but not pre-dose, scores for vigilance and TR were significantly lower overall in poor compared with normal sleepers. Despite the baseline differences between poor and normal sle epers, the changes following caffeine administration were similar in d irection and magnitude in both groups.