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A 2013 study in mice found that the brain cleared amyloid-beta, a protein that builds up in Alzheimer's disease, faster during sleep. A 2024 mouse study, which used a small fluorescent dye and different methods, found clearance was slower during sleep. Scientists are still debating how sleep affects the brain's waste removal.

Sleep science

Health

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The 2013 study came from Maiken Nedergaard's laboratory at the University of Rochester, which in 2012 had described what it called the glymphatic system: cerebrospinal fluid, the clear liquid around the brain, flows in along channels around blood vessels and washes through the tissue. Her team reported that the space between brain cells widened by about 60% during sleep, letting fluid flow more freely. In 2024 Nick Franks and William Wisden at Imperial College London measured the movement of dyes directly and found clearance markedly reduced in sleeping and anaesthetised mice. In 2025 Nedergaard's group reported that during non-REM sleep, the stages without the rapid eye movements of dreaming sleep, which fill most of the night, slow waves of the chemical messenger noradrenaline make blood vessels tighten and relax, pumping fluid into the brain. The methods differ, and none of these studies was in humans.

Türkçe oku
2013'te farelerde yapılan bir çalışmaya göre beyin, Alzheimer hastalığında biriken beta-amiloid proteinini uykuda daha hızlı temizliyordu. 2024'te yine farelerde, ama parlayan küçük bir boya ve başka yöntemlerle yapılan bir çalışma ise uykuda temizliğin yavaşladığını buldu. Uykunun bu temizliğe etkisi hâlâ tartışılıyor.

2013 çalışması, Rochester Üniversitesi'nde Maiken Nedergaard'ın laboratuvarından çıktı. Aynı ekip 2012'de “glimfatik sistem” adını verdiği bir temizlik yolu tanımlamıştı: Beyni çevreleyen berrak sıvı, yani beyin omurilik sıvısı, kan damarlarının çevresindeki kanallardan beynin içine akar ve dokuyu yıkar. Ekip, uykuda beyin hücreleri arasındaki boşluğun yaklaşık %60 genişlediğini ve sıvının daha rahat aktığını bildirdi. 2024'te Imperial College London'dan Nick Franks ile William Wisden boyaların hareketini doğrudan ölçtü ve uyuyan ya da narkoz altındaki farelerde temizliğin belirgin biçimde azaldığını buldu. 2025'te ise Nedergaard'ın ekibi şunu bildirdi: Gecenin büyük bölümünü oluşturan REM dışı uykuda, yani rüyalarla ilişkili hızlı göz hareketlerinin görülmediği evrelerde, kimyasal haberci noradrenalinin düzeyi yavaş dalgalar hâlinde inip çıkıyor. Bu dalgalar kan damarlarını düzenli olarak daraltıp gevşetiyor ve sıvıyı bir pompa gibi beyne itiyor. Çalışmaların yöntemleri farklı ve hiçbiri insanlarda yapılmadı.

Sources and further reading

Background reading: Glymphatic system
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