Not getting enough sleep doesn’t feel good — and could have some scary long-term consequences.
Insufficient or poor-quality sleep has been shown to wreck short term memory, cause weight gain, and increase the risk of diseases ranging from depression to cancer. And according to several newly published studies, there are a number of connections between disrupted sleep and the presence of biological signs and risk factors of Alzheimer’s disease.
People with Alzheimer’s generally have observable tangles of tau proteins, inflammation in the brain, damaged brain cells, and higher concentrations of beta-amyloid proteins, which make up a plaque associated with the disease.
And these biomarkers are more prevalent in people who regularly sleep poorly. Plus, new research suggests that disrupting sleep during certain parts of the night can quickly raise levels of Alzheimer’s-related proteins in the brain and spinal fluid.
How poor sleep changes your brain
Scientists behind a recent study published in the journal Neurology analysed 101 late-middle-aged adults (the average age was just under 63), and collected spinal fluid samples from each participant. The participants all had some increased risk for Alzheimer’s due to their family history and genetic factors, but all were cognitively healthy.
Researchers found that age differences within the group didn’t seem to affect levels of Alzheimer’s biomarkers. However, the people who reported not sleeping well, having sleep problems, or feeling sleepy during the day had more biomarkers of Alzheimer’s disease in their cerebrospinal fluid.
Another study published July 10 in the journal Brain involved 17 healthy volunteers (men and women between 35 and 65 years of age). That’s a small sample, but enough to show a biological effect. Researchers had the participants sleep while wearing headphones and monitored their brain activity.
In one sleep session, the volunteers rested normally through the night. But in another session, a tone would wake them and prevent them from entering a slow-wave sleep stage. The morning after each session, researchers collected cerebrospinal fluid using a spinal tap.
After the night with disrupted sleep, the researchers found people had higher levels of beta-amyloid proteins, the proteins that clump together and form the plaque found in Alzheimer’s-afflicted brains, in the volunteers’ spinal fluid. A week after those disrupted nights, researchers found higher levels of Tau, the tangled proteins also associated with Alzheimer’s, in the volunteers’ spinal fluid as well. (Tau generally takes longer to show up.)
The cleansing effect of sleep
The researchers behind the study that disrupted volunteers’ sleep suggested there may be a nasty cycle at work in the relationship between bad sleep and increased Alzheimer’s risk. If disrupted nights cause Alzheimer’s biomarker levels to spike, they said, that could further worsen sleep, which could then cause more buildup.
One of the functions of sleep is to wash neurotoxins from the brain, including beta-amyloid proteins, which other research has shown can worsen sleep.
“Because brain cells release amyloid beta during activity, we think if the brain cells can’t rest the way they’re supposed to and get that deep sleep, they produce a relative excess of amyloid,” Dr. Yo-El Ju of Washington University, an author of that study, told Reuters.
In the study that analysed poor sleepers, however, it’s impossible to say whether poor sleep caused the increase in Alzheimer’s markers or whether the fact that these individuals’ brains were changing is what caused them to have poor sleep. Both are likely true — not getting enough sleep could increase Alzheimer’s risk (as the second study shows), and the factors that lead to Alzheimer’s also seem to make it hard to sleep.
Regardless of the mechanisms and levels of risk, the authors of both studies write that improving sleep should be considered a priority. In a commentary published alongside the Neurology study, two doctors — Adam Spira of Johns Hopkins University and Yo-El Ju of Washington University — emphasised the potential benefits of facilitating better sleep.
“Effective interventions are available to treat causes of poor sleep, so identifying and treating sleep disturbances in preclinical [Alzheimer’s disease] may be a critical strategy to prevent or delay impending cognitive decline,” they wrote.
These results should not be interpreted as a reason to stress about a few bad nights, however.
“I don’t think people should worry about Alzheimer’s disease after one bad night,” Ju told Reuters.” I do think chronic sleep disruption increases the risk of Alzheimer’s disease.”
That should be some serious motivation to try to get more sleep.