Page 4 - December 2025 newsletter

Coffee naps might be the mission and release of neurotransmitters,” says Scott Riv-
kees, a pediatric endocrinologist and professor at Brown’s
weirdest—and smartest— School of Public Health. The effect is like a mental dimmer
way to recharge switch: the binding inhibits neural activity, making us feel
sleepy. As we sleep, adenosine is broken down until the
brain can resume normal functioning.
It sounds backward, but research suggests a cup of coffee
followed by a short nap could sharpen focus and fight
(You actually can consume too much caffeine. Here are
fatigue
the risks.)

In today’s caffeine-fueled culture, energy drinks and sleep Caffeine exploits this system to keep us awake. “[Caffeine
hacks promise sharper focus and longer days. But one is] a potent adenosine antagonist that will block adenosine
deceptively simple strategy keeps resurfacing: coffee with at each of the different receptor subtypes,” Rivkees says.
a nap. With those receptors occupied, adenosine can’t dock and
slow brain activity. Instead, nerve cells keep firing, neuro-
Of course, the so-called “caffeine nap” isn’t entirely novel. transmitters keep flowing, and we feel alert.
In Spain, for instance, it’s common to follow lunch with a
“It’s this yin-yang relation-
ship,” Rivkees says. The more
caffeine you consume, the
greater the number of recep-
tors that are filled—though
there is a physiological limit.
“When you have really high
concentrations of caffeine,
you will block the majority of
adenosine receptors.”

This relationship isn’t static,
however. As caffeine blocks
adenosine receptors, the
body compensates by gener-
ating more of them. Over
time, it takes higher doses of
caffeine to achieve the same
coffee and a short siesta. But only recently have experts effect—leading to tolerance
begun investigating whether there’s any scientific merit to and dependence at the molecular level.
this practice.
What the research says about caffeine naps
So, could a pre-siesta coffee give your brain a bigger boost
than either alone? Endocrinologists and sleep experts dis- Both naps and caffeine can reset the brain—naps by clear-
cuss the molecular underpinnings and potential limitations ing out adenosine, caffeine by blocking it. But, some have
of the caffeine nap. long wondered, might a short nap after a cup of coffee am-
plify the stimulant’s effect?
The yin-yang of caffeine and adenosineSleepiness isn’t just
a feeling—it’s chemical and biological processes at work.In
humans, one of the key players is adenosine, a neuromodu- The idea has intuitive appeal. “A nap itself combats
lator that steadily builds up in the brain as our cells burn sleepiness. Caffeine itself also combats sleepiness. So, if
energy over the course of a day. As adenosine accumu- we combine both, we could have a stronger effect,”
lates, it binds to a family of specialized receptors—A1, A2A, says Seiji Nishino, a professor emeritus of psychiatry,
A2B, and A3—that help regulate critical cellular functions, behavioral sciences, and sleep medicine at Stanford.
including sleep. Conveniently, caffeine takes about 20-30 minutes to
kick in, roughly the length of an ideal nap. “If we sleep
“When activated, [the receptors] slow nerve trans- longer than 30 minutes or an hour, we go into deep