Caffeine

Caffeine and insomnia:

Sleep disturbance by caffeine varies in individuals:

The way in which one’s body metabolizes caffeine may determine the way it influences a person’s sleep patterns. In a study by Levy M. et al, different individuals have been found to metabolize caffeine at different rates. Slower blood clearance and higher blood concentrations of caffeine at midnight were found in six healthy individuals with caffeine-induced wakefulness. Six other subjects in the study were not adversely affected by caffeine, indicating that differences in caffeine metabolism may be a cause of sleep disturbance. Participants with caffeine-induced wakefulness had a longer mean plasma half-life of 7.4 hours and a slower mean plasma clearance compared to those not affected by caffeine. (3)