Do you sleep poorly? Your brain may age faster.

We spend almost a third of our lives sleeping, but those hours are anything but wasted time. During sleep, the body repairs itself, and the brain gets the chance to protect itself and clear out clutter. Those who sleep poorly will notice this in their brains in the long run.

A major study from Sweden's Karolinska Institutet, published in early October, shows that people with disturbed sleep patterns have older brains than their actual age suggests.

The researchers examined sleep habits and brain scans of over 27,000 Britons between the ages of 40 and 70. They found that people who sleep poorly have brains that, on average, look almost a year older than expected.

And that has serious consequences: according to scientists, an older-looking brain appears to be associated with faster cognitive decline, a greater risk of dementia and even an increased chance of premature death.

Sleep quality is complex. The researchers therefore looked at five factors: whether someone is a morning or evening person, how many hours they sleep on average, and whether they suffer from insomnia, snoring, or extreme daytime sleepiness.

Those who scored well on four or five of these points were considered healthy sleepers. People with zero or one good quality, the poor sleepers, had brains that appeared on average a year older than their actual age. Night owls and those who slept too little or too much, in particular, lagged behind.

Looking a year older may sound harmless, but the effects are cumulative. Small accelerations in brain aging can contribute to memory problems or neurological diseases in the long term.

A key explanation is inflammation. Poor sleep increases inflammation levels in the body, which in turn can damage brain tissue and blood vessels. The glymphatic system, the brain's natural cleansing system, which is primarily active at night, also functions less effectively in people who sleep too little or restlessly. This leads to the accumulation of harmful substances.

In addition, chronic sleep deprivation increases the risk of diseases such as obesity, type 2 diabetes and cardiovascular disease, all of which impact brain health.

The researchers emphasize that sleep habits can be adjusted. A regular sleep schedule, less caffeine and screen time before bed, and a dark, quiet bedroom can all make a big difference.

According to lead researcher Abigail Dove, the results are a warning, but also an opportunity: "We can't prevent brain aging, but we can influence how quickly it happens. Those who take their sleep seriously keep their brains young longer."