It is commonly advised to avoid caffeine before bed. Now a study by US researchers also supports the same. Researchers observed that drinking coffee before bedtime disrupts the body's internal clock, making it harder for an individual to get to sleep on time and makes it more challenging to wake up in the morning.
The researchers said, "The findings in the Science Translational Medicine
not only explain why evening caffeine-drinkers may stay up, and wake up late, but could also offer travelers a way to time their caffeine use in order to limit the effects of jet lag."
For the study, five volunteers were randomly assigned to consume as much caffeine as contained in a double espresso three hours before bed, while others were exposed to bright lights, or were given a placebo. Over the course of 49 days, the researchers studied the volunteers under various conditions. Their saliva was regularly tested for levels of the hormone melatonin, which naturally regulates sleep and waking cycles.
The study said, "They found that those who took caffeine in low-light conditions experienced about a 40-minute phase delay of the circadian melatonin rhythm. Those who were exposed to bright overhead lights three hours before bed saw their circadian clocks bumped back by 85 minutes. Those who took both the caffeine and sat under bright lights were disrupted by 105 minutes."
Professor Kenneth Wright of the University of Colorado, Boulder, said, "This is the first study to show that caffeine, the mostly widely used psychoactive drug in the world, has an influence on the human circadian clock. It also provides new and exciting insights into the effects of caffeine on human physiology."
The study raises the intriguing possibility that proper use of caffeine could help reset the body's clock in order to avoid jet lag. However, more research is needed to determine how travelers crossing time zones can best use caffeine to stay alert. The study said, "It will be important to monitor for caffeine-induced sleep disruption under such conditions, which could worsen jet lag."