We are proud to feature this expert insight from master teacher Dr. Sara Elizabeth Ivanhoe. With a background that spans 30 years of teaching and a Ph.D. focused on sleep philosophy, Sara serves as a trusted guide for the Glo community. Here she unpacks the complex relationship between caffeine and the body, explaining why cutting off caffeine early isn’t always enough and offering science-backed adjustments to help your body truly settle down for the night.
For years, I consumed caffeine (dark chocolate) between 3:00 and 4:00 p.m., assuming it would be long out of my system by the time I wanted to sleep around 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 can take for the body to unwind from caffeine’s effects even after the caffeine itself has cleared. Elevated blood pressure and heart rate, jaw tension, feeling fidgety and “all over the place,” did not resolve on the same timeline. Let’s take a look at how this works…
Sleep and stress exist in a bidirectional relationship often referred to as the sleep–stress cycle. Many of us already know that stress activates the sympathetic nervous system, increasing arousal at precisely the time when the body should downregulate in order to initiate and maintain sleep. In turn, insufficient or fragmented sleep heightens stress reactivity the following day by amplifying emotional responsivity, impairing prefrontal regulatory control, and altering cortisol rhythms. This negative feedback loop helps explain why feeling exhausted does not necessarily translate into being able to sleep; an overtired nervous system is often a stimulated one, not a settled one.
One factor commonly underestimated within this cycle is caffeine. Caffeine works primarily by blocking adenosine, a chemical that builds up in the brain throughout the day and helps create the feeling of sleepiness, known as “sleep pressure.” Under normal circumstances, rising adenosine levels signal that the body is ready for rest. When caffeine blocks this signal, we feel more alert and less tired—even though the body’s actual need for sleep has not changed. Beyond this well-known effect, caffeine also influences the cardiovascular and neuromuscular systems. It increases heart rate and blood pressure, elevates circulating catecholamines, and often increases baseline muscle tone. For many people, this shows up as subtle but persistent tension—jaw clenching, shoulder elevation, nail biting, and restlessness.
Caffeine is often discussed in terms of its half-life, commonly estimated at approximately six hours in healthy adults. A half-life refers to the amount of time required for the body to metabolize and eliminate half of a substance from the bloodstream. While this metric is useful, it is frequently misunderstood. The metabolic clearance of caffeine does not mean that its downstream physiological effects resolve at the same pace. Even after caffeine has left the system, the body may still be holding onto its effects, including muscle tension and a heightened stress response. Factors such as co-ingestion with food (particularly protein), individual differences in metabolism, and hormonal fluctuations can further extend caffeine’s functional impact.
If you’re drinking caffeine in the afternoon and still struggling to sleep at night, you’re not imagining things—and it’s not simply a matter of not meditating correctly or “poor sleep hygiene.”
The practical takeaway is simple: if you regularly consume caffeine in the afternoon and struggle with sleep, consider moving that intake earlier—closer to lunchtime, especially if you eat a high-protein meal, which can slow caffeine clearance. Doing so can provide the desired afternoon energy boost while allowing sufficient time not only for caffeine to leave the system, but for the nervous system to return to a more settled, sleep-ready state.
By: Dr. Sara Elizabeth Ivanhoe
Interested in hearing more? Join us on February 3, 2026 for a live workshop with Dr. Ivanhoe: Sleep, Stress, and Women’s Health: Breaking the Cycle. We’ll explore the link between sleep, stress, and well-being through gentle movement, mindful breathwork, and an open Q&A to help you restore balance, regulate your nervous system, and break the cycle of stress and sleeplessness.