Sleep and memory: why studying less at night can improve learning

For many students, especially when an important exam is approaching, cutting back on rest may seem like a sensible way to create extra study time. Neuroscience, however, suggests that this decision may not be as beneficial as it appears. Sleep is more than a period of rest: it plays an important role in consolidating learned information.

The 2025 meta-analysis “Bayesian meta-analysis reveals the mechanistic role of slow oscillation-spindle coupling in sleep-dependent memory consolidation”, published in the scientific journal eLife, brought together data from 23 studies and 297 effect sizes to examine the link between sleep mechanisms and memory retention. The research found an association between the precise, strong coupling of two brain-activity patterns that occur during deep sleep - slow oscillations and so-called sleep spindles - and the consolidation of memories.

According to Renato Gama, a doctor and postgraduate Neurology lecturer at Afya Educação Médica in Rio de Janeiro, the brain does not simply “switch off” while we sleep. Instead, it undergoes essential processes that turn recent information into more stable memories.

“During sleep, particularly in its deeper stages, the brain reorganises the information acquired while we are awake. It is as though it selects and integrates what has been learnt, strengthening certain connections between neurons. That is why sleeping after studying is part of the learning process, rather than an interruption to it,” says the neurologist.

Sleep helps consolidate memory

Over the course of a day, a student encounters a substantial amount of information. Some of it remains temporarily accessible, but that does not mean it has been established as long-term memory.

Different mechanisms operating during sleep support this consolidation. The same eLife study looked specifically at the relationship between slow oscillations and sleep spindles. Its findings indicated that the more accurate and stronger the coupling between these two activity patterns is during deep sleep, the greater the tendency for information to be retained.

This phenomenon is particularly seen in the frontal lobe and is linked to how the brain processes and stabilises previously acquired memories. For Renato Gama, this helps explain why spending longer in front of books does not always mean learning more.

“There is a difference between being exposed to content and actually learning it. A student may spend five or six hours reading, but if they are sleep-deprived, they may struggle to consolidate what they have studied. Memory depends both on the moment when we take in information and on what the brain subsequently does with it.”

Does studying until the early hours hinder learning?

The early hours themselves are not necessarily the problem. The key issue is giving up sleep to extend study time. Someone may prefer studying at night and still perform well if they can maintain an adequate, regular sleep schedule. Difficulties arise when night-time study is extended at the expense of rest. In that situation, the student cuts short the very period in which the brain carries out important memory-consolidation processes.

Sleep deprivation can also impair functions needed for studying itself, including attention, concentration, processing speed and the ability to retrieve information. “If a student studies all night and sleeps for only a few hours, they do not merely lose their rest period. The following day, they may have reduced attention, increased sleepiness and trouble accessing information that was already available. This can create a cycle: they study more, sleep less, learn less efficiently and need even more time to study,” explains the Afya doctor.

Adequate rest is essential for learning

According to the specialist, sleeping after studying matters just as much as studying. Ideally, sleep should be built into an exam preparation routine, rather than viewed as something that can be removed when material begins to pile up.

Memory also depends on other factors, including the type of information learnt and individual characteristics. The meta-analysis itself identified differences associated with memory type, ageing, spindle frequency and where these events occur in the brain.

For those preparing for university entrance examinations and civil service exams, then, sleep should not be treated as wasted time. Studying, taking breaks, reviewing material and sleeping are all parts of the same learning process.

“There is no genuine benefit in routinely trading sleep for additional study hours. The best performance comes when a student can balance acquiring knowledge with recovery. Sleep is not what happens after learning: it also contributes to building memory,” Renato Gama concludes.

By Maria Clara Montanha