World Brain Day 2026: Doctor explains why your brain stays active even during sleep

Even when the body is at rest, the brain remains remarkably active.

Sleep is not a passive state but a highly organised process during which the brain performs some of its most essential functions. From repairing cells to strengthening memories and regulating emotions, what happens during sleep is critical for long-term brain health.

This World Brain Day 2026, Dr S Suresh Sagadevan, Pulmonologist and Sleep Medicine Specialist, Gleneagles Hospitals Chennai, explains that many people underestimate the importance of sleep quality, focusing only on duration.

“Many people think getting 7-8 hours of sleep is enough, but the quality of sleep is just as important as the number of hours,” says Dr Sagadevan.

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What happens in the brain during sleep

Sleep occurs in cycles, each consisting of different stages that play distinct roles in maintaining brain function. These include non-rapid eye movement (NREM) sleep and rapid eye movement (REM) sleep.

“During sleep, the brain goes through different stages, and each stage has an important role,” explains Dr Sagadevan.

Deep sleep, a stage of NREM sleep, allows the body to recover and repair itself, while REM sleep is when the brain becomes more active, supporting memory, learning and emotional processing.

“Deep sleep helps the body recover, while REM sleep supports memory, learning and emotional well-being,” he adds.

Why sleep quality matters more than you think

While getting enough hours of sleep is important, uninterrupted and high-quality sleep is essential for the brain to complete these stages effectively.

“If these sleep stages are repeatedly disturbed, the brain doesn't get the recovery it needs,” notes Dr Sagadevan.

When sleep quality is poor, the brain cannot perform its restorative functions efficiently, leading to both immediate and long-term consequences.

The impact of poor sleep on brain health

Poor-quality sleep often shows up quickly in daily life. People may feel tired, irritable or unable to concentrate, even after spending enough time in bed.

“Poor-quality sleep can leave you feeling tired, irritable and unable to concentrate the next day,” says Dr Sagadevan.

Over time, "it can affect memory, productivity and mental well-being,” he shares.

Chronic sleep issues are also linked to a higher risk of several health conditions.

“It may also increase the risk of conditions such as high blood pressure, diabetes, obesity and depression, all of which can have an impact on overall brain health,” warns Dr Sagadevan.

Sleep and emotional wellbeing

Sleep plays a crucial role in regulating emotions and maintaining mental balance. When the brain does not get adequate rest, emotional responses can become harder to manage.

“REM sleep supports emotional well-being, and without it, people may feel more stressed or emotionally overwhelmed,” explains Dr Sagadevan.

This connection highlights why sleep is closely linked to mental health conditions such as anxiety and depression.

Signs your sleep may not be healthy

Not all sleep problems are obvious. Some people may spend enough time in bed but still experience poor-quality sleep due to underlying issues.

“If you regularly snore loudly, wake up frequently during the night or feel sleepy during the day despite getting enough sleep, it's important to consult a doctor,” advises Dr Sagadevan.

These symptoms may indicate sleep disorders that require medical attention.

Simple ways to improve sleep quality

Improving sleep quality often starts with small but consistent lifestyle changes. Maintaining a regular sleep schedule and creating a restful environment can make a significant difference.

“Try to sleep and wake up at the same time every day, avoid screens for at least an hour before bedtime, limit caffeine late in the day, and keep your bedroom quiet, dark and comfortable,” recommends Dr Sagadevan.

These habits help the brain transition smoothly into sleep and maintain healthy sleep cycles.

The bottom line

Sleep is not just about rest - it is a vital process that allows the brain to repair, reset and function effectively. Prioritising quality sleep can have a profound impact on both physical and mental health.

“Good sleep is not just about sleeping longer; it's about sleeping better. Quality sleep is essential for a healthy brain, a healthy body and overall well-being,” emphasises Dr Sagadevan.

Ignoring sleep problems can lead to long-term consequences, but early intervention can make a difference.

“If you have ongoing sleep problems, don't ignore them. They are often treatable and seeking help early can make a big difference,” he concludes.

Understanding that the brain never truly switches off may be the key to taking sleep more seriously - and protecting brain health for years to come.