Daijiworld Media Network - New Delhi

New Delhi, May 30: Consuming caffeine in the evening may not always reduce sleep duration or make it harder to fall asleep, but it can significantly affect the quality of sleep and the brain's ability to recover during the night, according to a new study.

Researchers, including scientists from Wroclaw Medical University, analysed 32 studies examining the relationship between caffeine consumption and sleep-related brain activity.

The findings, published in the journal Nutrients, suggest that caffeine alters the brain's sleep patterns in ways that may not be noticeable to individuals despite appearing to get adequate rest.

The researchers used electroencephalography (EEG), a technique that records the brain's electrical activity, to assess sleep quality.

Donata Kurpas said EEG enables scientists to observe not only whether a person is asleep, but also how the brain functions during sleep.

“EEG allows us to see not only whether a person is sleeping, but also how the brain is sleeping,” Kurpas said.

According to the study, caffeine can reduce slow-wave activity, a crucial component of deep sleep responsible for physical recovery, energy restoration and healthy brain function.

Researchers found that even when sleep duration appears normal, caffeine may shift brain activity towards a more wakeful state, reducing the restorative benefits of sleep.

The study concluded that caffeine consistently alters the neurophysiological structure of sleep, leading to reduced sleep depth and weaker recovery processes.

It also found evidence that caffeine increases the complexity of brain activity during sleep, resulting in a more excitation-dominant state.

The researchers noted that a person may spend eight hours in bed and feel they have slept well, while the brain may not have achieved sufficient deep sleep for full recovery.

“The subjective feeling of having slept well does not always correspond to what we observe in neurophysiological recordings,” Kurpas said.

She added that caffeine should not be viewed as inherently harmful or beneficial, but rather as a biologically active substance whose effects vary depending on factors such as dosage, timing of consumption, age, stress levels, sleep habits and individual sensitivity.

The findings underscore the importance of considering not just the quantity of sleep, but also its quality when evaluating the impact of caffeine consumption on overall health and well-being.