![\"Figure](\"https:\/\/www.ecoticias.com\/en\/wp-content\/uploads\/2026\/11\/filad01-m1-csf-flow-sleep-figure.jpg\")
A 3.82 versus 1.15 decibel gap<\/h2>\n\n\n\n
When the younger adults slipped into non-REM sleep, their slow waves grew stronger. Their CSF waves grew larger, as Lewis had seen before. Among the older adults, the average CSF waves were significantly smaller.<\/p>\n\n\n\n
Here the paper gets specific. Low-frequency CSF power rose by an average of 3.82 decibels from waking to sleep in the young group, against 1.15 decibels in the older group. Among the older volunteers, the authors found “no significant increase” from wake to sleep.<\/p>\n\n\n\n
Older adults also had less flow while awake, but the gap was larger during sleep. The link between blood volume swings and fluid movement weakened too. Its peak correlation was 0.67 in the young group and 0.42 in the older one.<\/p>\n\n\n\n
Checkerboards and held breaths<\/h2>\n\n\n\n
To find the cause, the team ran daytime tests on 31 young and 55 older volunteers. In one task, they watched a checkerboard flickering 12 times a second. That kind of image normally raises neural activity and the blood supply that follows it.<\/p>\n\n\n\n
In many older subjects, neural activity went up but blood flow barely followed. That points to weaker neurovascular coupling, the process in which busy brain areas get extra blood from nearby vessels.<\/p>\n\n\n\n
A second task asked people to hold their breath eight times, for 15 seconds each. Holding the breath raises carbon dioxide in the blood, which normally boosts blood flow in the brain. That response was smaller in the older participants.<\/p>\n\n\n\n
A statistical model built by the team showed that these two factors explained much of the drop in CSF flow, but not all of it. “Aging is so complex, and so many different things change, that it’s really hard to disentangle the individual factors,” Bailes said.<\/p>\n\n\n\n
Frontal gray matter tracked the flow<\/h2>\n\n\n\n
None of the volunteers had a diagnosed neurodegenerative disorder. Even so, some older adults showed signs of gray matter atrophy. That shrinkage went along with a greater decrease in CSF flow.<\/p>\n\n\n\n
The link appeared in the frontal lobe, where sleep slow waves are strongest, and not in other lobes. The brain already changes course at several ages<\/a> across a lifetime. MIT also points out that earlier studies tied disturbed sleep to a higher risk of Alzheimer’s and other dementias.<\/p>\n\n\n\n Lewis said that “people age really differently.” Her team now wants to follow some participants over time, to see whether changes in fluid flow go along with a higher risk of neurodegenerative disorders, which include the disease targeted in recent Alzheimer\\’s research in mice<\/a>.<\/p>\n\n\n\n In an earlier study, Lewis’s lab found that short bursts of “pink noise” during sleep<\/a> could boost CSF flow in younger adults. That sound has not yet been tried on older sleepers. Nobody can say yet whether it would help them.<\/p>\n\n\n\n Sleep is not the same everywhere, either: one marine mammal sleeps with half its brain awake<\/a>.<\/p>\n\n\n\n The study also cannot separate cause from effect. Lost gray matter could weaken slow waves, or reduced fluid flow could harm neurons over time. The authors list three such options and say future studies will be needed to tell them apart.<\/p>\n\n\n\n Some older volunteers did not fit the pattern at all.<\/p>\n\n\n\n “It’s really intriguing that for some of these older adults, their CSF fell right in the range of the healthy young adults,” Lewis said. Her team plans to look at what sets those people apart.<\/p>\n\n\n\n The full study was published in Nature Aging<\/a>, and MIT described the work in a news release<\/a> the same day.<\/p>\n\n\n\n Image: Williams et al. \/ PLOS Biology, CC BY 4.0<\/p>\n","protected":false},"excerpt":{"rendered":" Older brains move less cerebrospinal fluid during deep sleep, and that fluid is part of how the brain gets rid … <\/p>\nPink noise untested after 60<\/h2>\n\n\n\n