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Sleep disruptions related to changes in immune cells in brain and worse cognition: study

December 17, 2019

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About 35 million people worldwide have dementia, an umbrella term describing a decline in mental abilities like memory, language and reasoning. Studies have associated broken sleep with impaired thinking and dementia, but the precise reasons for this are unclear. A study published in Science Advances by Dr. Andrew Lim, a scientist in the Hurvitz Brain Sciences Research Program at Sunnybrook Research Institute, may provide insight into the connection.

In people who were aged over 65 years, Lim and colleagues found that fragmented slumber was associated with changes in the microglia, a type of immune cell in the brain, and poorer performance on cognitive tests. Microglia help fight infections and clear waste from the brain; Lim notes, however, that dysfunction of microglia seems to be involved in development of Alzheimer’s disease.

The researchers looked at 685 adults who participated in two large U.S. studies. They examined their sleep, results from thinking tests and, later, did an autopsy of donated brain tissue samples. Disruptions in sleep were measured using a wristwatch-like device worn by the participants that can detect when someone awakens at night.

Greater sleep fragmentation was associated with more activated microglia and higher gene expression characteristic of “older” microglia—where the microglia appears to come from an older person. In turn, more activated microglia or genetically older microglia were associated with worse cognition. Those with poorer quality shut-eye also did worse on cognitive tests.

In conclusion, the results suggest that sleep disruptions are tied to microglial aging and activation, which may explain in part their relation to cognitive impairment, say the researchers.

The study was published in Science Advances.

» Read the full story at The Globe and Mail