Scientists have long been puzzled over how the brain clears away its own waste. Unlike the rest of the body, which relies on the lymphatic system to carry waste from cells into circulation, the brain appeared to have no such mechanism. That mystery shifted about 12 years ago when researchers discovered the glymphatic system, a network that acts as the brain’s built-in cleaning service.The glymphatic system works by circulating cerebrospinal fluid (CSF) through the brain’s tissues. This fluid enters the spaces between brain cells, collects waste, and carries it out along large veins. In animal studies, particularly in mice, the system appears most active during sleep. That discovery suggested that sleep might be essential for brain detoxification, and disrupted rest could interfere with waste clearance.Among the most important toxins flushed out by the glymphatic system is amyloid beta (Aβ), a protein that, when accumulated, forms sticky plaques in the brain. These plaques, along with tangles of tau protein, are a defining feature of Alzheimer’s disease—the most common cause of dementia worldwide.The idea that better sleep helps the brain clean itself is more than a scientific curiosity. It may help explain why people who consistently struggle with poor sleep face higher risks of dementia.In humans, levels of amyloid beta in cerebrospinal fluid rise during waking hours and drop during sleep, suggesting that rest is when the brain “takes out the trash.” In one striking experiment, researchers kept healthy adults awake for a single night. Just 24 hours of sleep deprivation increased amyloid beta in the hippocampus, the brain region essential for memory and one of the first to show damage in Alzheimer’s disease.Still, questions remain. While several mouse studies indicate the glymphatic system is most active at night, other recent experiments suggest it may work differently depending on the time of day or even the species. The debate highlights how much more we need to learn about how this system functions in humans.How Do Sleep Disorders Increase Risk of Dementia?Not all sleep is equal. Short-term sleep loss is harmful, but chronic sleep problems can be particularly damaging to brain health.Sleep ApnoeaSleep apnoea, where breathing repeatedly stops and starts during sleep, deprives the brain of oxygen and fragments rest. Both oxygen deprivation and chronic sleep disruption are thought to contribute to toxin build-up in the brain. Importantly, studies show that patients treated for sleep apnoea—often with continuous positive airway pressure (CPAP) machines—see greater clearance of amyloid beta. This suggests that treatment may help restore the brain’s waste-disposal rhythm.InsomniaInsomnia, defined as difficulty falling or staying asleep, has also been linked to higher dementia risk. While the association is clear, the mechanism is less so. Does insomnia accelerate amyloid build-up? Could treatment reverse the trend? Researchers are only beginning to explore whether therapies—such as orexin receptor antagonists, a new class of sleep drugs—might improve toxin clearance.Untreated sleep disorders don’t just leave you tired—they may be undermining your brain’s long-term health.Can Sleep Prevent Dementia?While early findings are promising, science isn’t yet ready to declare sleep a cure for dementia. What researchers do know is that sleep deprivation can rapidly alter amyloid levels in the brain, and chronic sleep disorders such as apnoea and insomnia are associated with a higher risk of developing dementia. Treating sleep apnoea appears to improve amyloid clearance, though evidence regarding the effects of insomnia treatment remains limited.What remains uncertain is whether improving sleep directly reduces dementia risk. Large, long-term clinical studies are still needed to confirm the link. Researchers are actively pursuing this question, measuring proteins like amyloid beta and tau in blood and spinal fluid across sleep-wake cycles, in both healthy individuals and those with sleep disorders.The global dementia burden is growing. Alzheimer’s and related dementias currently affect more than 55 million people worldwide, with cases expected to triple by 2050. While scientists race to develop new drugs, lifestyle measures—such as improving sleep—are emerging as powerful, accessible tools for prevention.If better sleep helps the glymphatic system flush out harmful proteins, prioritizing rest may be one of the simplest ways to protect long-term brain health. That means:Maintaining a consistent sleep schedule.Addressing sleep disorders like apnoea with medical guidance.Seeking help if insomnia is chronic.While the science continues to evolve, the advice remains practical: treat sleep as essential, not optional.The glymphatic system is a reminder that the brain, like the body, needs maintenance. Just as poor diet, smoking, or lack of exercise take their toll, chronic sleep disruption may leave toxins lingering in the brain, setting the stage for cognitive decline.The exciting part is that this field of research is still in its infancy. Scientists are mapping the biology of how the brain cleans itself and testing new ways to boost that process. Whether through targeted drugs, therapies for sleep disorders, or simply protecting natural sleep cycles, the future may bring strategies to slow or even prevent dementia.