Researchers Link Alzheimer's to a Lack of ZZZZZs Sleep-Deprived Mice Develop More Plaques in Their Brains
Saey, Tina Hesman, Science News
Losing sleep could lead to losing brain cells, a new study suggests.
Levels of a protein that forms the hallmark plaques of Alzheimer's disease rise in the brains of mice and in the spinal fluid of people during wakefulness and fall during sleep, researchers report online September 24 in Science. Mice that didn't get enough sleep for three weeks also had more plaques in their brains than well-rested mice, the team found.
Scientists knew that having Alzheimer's disease was associated with poor sleep, but they had thought that Alzheimer's disease caused the sleep disruption.
"This is the first experimental study that clearly shows that disrupted sleep may contribute to the disease process," says Peter Meerlo, a neuroscientist at the University of Groningen in the Netherlands. "It shows that chronic sleep loss, in the long run, changes the brain in ways that may contribute to disease." A vicious cycle could result if sleep loss leads to Alzheimer's disease and the disease leads to more sleep loss, he says.
Researchers led by David Holtzman of Washington University in St. Louis used a method called microdialysis to measure the levels of amyloid-beta protein in the fluid between brain cells of mice. Amyloid-beta sometimes twists into a sticky form and clumps together, forming plaques. Scientists don't yet understand how, but they think that amyloid-beta clumping eventually leads to the death of neurons and to Alzheimer's disease symptoms (SN: 8/16/08, p. 20).
Although levels of amyloid-beta in the brain tissue of the mice didn't seem to change, Holtzman's group found that levels of the protein released into brain fluid did rise and fall throughout the day. "We didn't know it would coordinate with sleep and wakefulness," Holtzman says.
Levels of the protein in the brain fluid increased in mice during the night-- when mice are mostly awake--and fell during the day when mice sleep. …