If you’ve passed the age of 40, you should be extra careful about consuming caffeine before bed. New research has discovered that the sleep of older adults is more sensitive to the effects of a higher dose of caffeine.
Caffeine elicits wakefulness by acting as a competitive antagonist at adenosine receptors in the brain. In other words, caffeine blocks the effects of adenosine, a neuromodulator that promotes sleepiness by reducing neuron activity.
“Surprisingly, the age-related modulation of caffeine effects on the sleep–wake cycle has received little attention,” lead researcher Rébecca Robillard and her colleagues wrote in their study, which was published online in the Journal of Psychopharmacology.
For their study, the researchers had 22 healthy 20–30 year old adults (the young group) and 25 healthy 40–60 year old adults (the middle-age group) sleep at a chronobiology laboratory for two nonconsecutive nights. After arriving at the lab, the participants consumed either a low dose of caffeine, a high dose of caffeine, or a placebo three hours before their normal bedtime.
Throughout the course of the study, participants also recorded their sleep and waking behaviors on a daily basis, and kept a daily log of the amount of caffeinated products they consumed.
“Compared to that of the young, the sleep of older adults was generally more sensitive to the effects of a higher dose of caffeine,” the researchers said.
Caffeine increased the length of time it took for the participants to fall sleep, shortened total sleep time and reduced sleep efficiency. But the researchers found that these effects were more pronounced in the middle-aged group.
“The effects of 200 mg of caffeine were similar across both age groups, but the 400 mg dose of caffeine increased sleep latency, shortened total sleep time and the absolute amount of stage 2 sleep, and reduced sleep efficiency more extensively in older compared to younger adults,” Robillard and her colleagues wrote.