For a lot of people, coffee is not optional. It is part of the routine. The day does not quite start without it. But then comes that common advice. Stop drinking it by mid-afternoon, usually around 3:00 pm. There is a reason behind that.
Caffeine does not leave your system quickly. If you drink it later in the day, it can stay active into the evening, overlapping with the time your body is trying to wind down. Dr Kunal Sood, an anaesthesiologist and interventional pain medicine physician, explained this in an Instagram video shared on March 27, breaking down how late caffeine intake affects sleep and recovery.
Late caffeine affects sleep quality and recovery
Dr Sood said, “Late caffeine shifts the brain into a more alert state at the wrong time. It alters sleep architecture, stress hormones, and next-day recovery.” He added, “It reduces sleep quality, not just sleep duration, which is why you can sleep ‘enough’ but still feel tired.”
Harder to fall asleep due to caffeine
Dr Sood explained how caffeine interferes with the body’s natural sleep signals. “Caffeine blocks adenosine receptors, preventing the buildup of sleep pressure,” he said. This increases sleep latency and delays the brain’s ability to recognise when it is time to sleep.
He also pointed out that caffeine stays in the body for a long time. “Effects can persist even when caffeine is consumed up to 6 hours before bedtime,” he said.
Reduced deep sleep and lighter sleep stages
Adenosine also plays a role in regulating deep sleep. When caffeine disrupts this, the quality of sleep drops. “Adenosine regulates slow-wave activity, the most restorative stage of sleep,” Dr Sood said.
He added, “Caffeine reduces slow-wave (deep) sleep and increases lighter sleep stages.” He also noted that systematic reviews show measurable reductions in deep sleep along with an increase in lighter sleep.
More nighttime awakenings and fragmented sleep
Caffeine also affects how stable your sleep is through the night. “Caffeine increases neuronal activity and sympathetic tone, creating physiologic hyperarousal during sleep,” Dr Sood said.
This can lead to more disruptions. “It leads to more wake after sleep onset and lower sleep efficiency,” he explained, meaning sleep becomes more fragmented and less restorative.
Caffeine raises cortisol levels
Dr Sood also spoke about the role of stress hormones. “Caffeine stimulates the HPA axis and increases cortisol secretion,” he said.
Since cortisol promotes wakefulness, higher levels in the evening can make it harder to fall asleep and stay asleep.
Next-day fatigue even after full sleep
Even if someone gets enough hours of sleep, the quality may not be the same. “Even if total sleep time appears adequate, reduced deep sleep and fragmented sleep impair recovery,” Dr Sood said.
He added that studies link caffeine-related sleep disruption to “next-day fatigue, reduced performance, and continued reliance on caffeine.”
Disclaimer: Tips and suggestions mentioned in the article are for general information purposes only and should not be construed as professional medical advice.
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