Sleep might be your brain’s nightly cleanup crew — and skipping it could be more dangerous than you think.

When you sleep, your brain actively flushes out toxic proteins that can build up and contribute to diseases like Alzheimer’s — and this cleanup doesn’t work as well if you’re not sleeping well. Other research shows that even in animals with early signs of brain disease, poor sleep seems to make the waste buildup worse, not just a side effect. One study even found that after a good night’s sleep, those same toxic proteins show up in the blood, which is strong evidence the brain is literally cleaning itself out. It’s not that sleep causes dementia — it’s that not sleeping well might let the damage sneak in.