We’re proud to characteristic this knowledgeable perception from grasp instructor Dr. Sara Elizabeth Ivanhoe. With a background that spans 30 years of educating and a Ph.D. targeted on sleep philosophy, Sara serves as a trusted information for the Glo group. Right here she unpacks the complicated relationship between caffeine and the physique, explaining why slicing off caffeine early isn’t all the time sufficient and providing science-backed changes to assist your physique really cool down for the evening.
For years, I consumed caffeine (darkish chocolate) between 3:00 and 4:00 p.m., assuming it might be lengthy out of my system by the point I needed to sleep round 10:30 or 11:00 p.m. On paper, that logic made sense. What I hadn’t factored in was the repercussive time—the hours it will probably take for the physique to unwind from caffeine’s results even after the caffeine itself has cleared. Elevated blood strain and coronary heart fee, jaw rigidity, feeling fidgety and “everywhere,” didn’t resolve on the identical timeline. Let’s check out how this works…
Sleep and stress exist in a bidirectional relationship sometimes called the sleep–stress cycle. Many people already know that stress prompts the sympathetic nervous system, growing arousal at exactly the time when the physique ought to downregulate with the intention to provoke and keep sleep. In flip, inadequate or fragmented sleep heightens stress reactivity the next day by amplifying emotional responsivity, impairing prefrontal regulatory management, and altering cortisol rhythms. This adverse suggestions loop helps clarify why feeling exhausted doesn’t essentially translate into having the ability to sleep; an overtired nervous system is commonly a stimulated one, not a settled one.
One issue generally underestimated inside this cycle is caffeine. Caffeine works primarily by blocking adenosine, a chemical that builds up within the mind all through the day and helps create the sensation of sleepiness, generally known as “sleep strain.” Below regular circumstances, rising adenosine ranges sign that the physique is prepared for relaxation. When caffeine blocks this sign, we really feel extra alert and fewer drained—regardless that the physique’s precise want for sleep has not modified. Past this well-known impact, caffeine additionally influences the cardiovascular and neuromuscular techniques. It will increase coronary heart fee and blood strain, elevates circulating catecholamines, and infrequently will increase baseline muscle tone. For many individuals, this exhibits up as refined however persistent rigidity—jaw clenching, shoulder elevation, nail biting, and restlessness.
Caffeine is commonly mentioned by way of its half-life, generally estimated at roughly six hours in wholesome adults. A half-life refers back to the period of time required for the physique to metabolize and eradicate half of a substance from the bloodstream. Whereas this metric is helpful, it’s continuously misunderstood. The metabolic clearance of caffeine doesn’t imply that its downstream physiological results resolve on the similar tempo. Even after caffeine has left the system, the physique should be holding onto its results, together with muscle rigidity and a heightened stress response. Components resembling co-ingestion with meals (notably protein), particular person variations in metabolism, and hormonal fluctuations can additional lengthen caffeine’s useful affect.
Should you’re consuming caffeine within the afternoon and nonetheless struggling to sleep at evening, you’re not imagining issues—and it’s not merely a matter of not meditating accurately or “poor sleep hygiene.”
The sensible takeaway is straightforward: in the event you commonly devour caffeine within the afternoon and battle with sleep, think about shifting that consumption earlier—nearer to lunchtime, particularly in the event you eat a high-protein meal, which might sluggish caffeine clearance. Doing so can present the specified afternoon power enhance whereas permitting adequate time not just for caffeine to go away the system, however for the nervous system to return to a extra settled, sleep-ready state.
By: Dr. Sara Elizabeth Ivanhoe
Serious about listening to extra? Be a part of us on February 3, 2026 for a reside workshop with Dr. Ivanhoe: Sleep, Stress, and Ladies’s Well being: Breaking the Cycle. We’ll discover the hyperlink between sleep, stress, and well-being by way of light motion, conscious breathwork, and an open Q&A that will help you restore steadiness, regulate your nervous system, and break the cycle of stress and sleeplessness.