Sleepless nights take their toll on the brain. More than it seems. Apart from tiredness or lack of concentration the next day, cognitive performance can suffer in the long term and in a more serious way. A study by the Pasqual Maragall Foundation, specialized in Alzheimer’s research, has found changes in brain structure that suggest a link between insomnia and the development of this neurodegenerative disease. The research, carried out with healthy people, has found that those who suffer from insomnia present changes in some areas of the brain that are also affected in the early stages of Alzheimer’s. Brain damage in this neurological condition sets in long before the patient develops the first symptoms.
It is not the first time that sleep disorders have been linked to a high risk of dementia. A study published in 2018 in the journal Alzheimer’s & Dementia already pointed out that insomnia in middle age is associated with a higher risk of this type of neurodegenerative ailments. Research by the Pasqual Maragall Foundation, carried out among 1,683 healthy people —615 with insomnia— and published in the journal Alzheimer’s Research and Therapy, finds that those participants with sleep disorders had a lower volume in brain regions such as the precuneus or the posterior cingulate cortex. “These are areas that participate in networks that work on memory function, performance… These areas are where neurological damage accumulates in the early stages of Alzheimer’s. Here it may be that they are accumulating damage or that, already by themselves, have less volume”, explains Oriol Grau, first signatory of the study.
In addition, the research has found changes in the white matter of the brain – where the axons are, the cables that connect some neurons with others. “We know that a disruption of this substance can have an effect on cognition. The profile of changes that we have found could suggest that there is a type of inflammation linked to insomnia. What we do not know is what the role of inflammation is,” he says. Grau. The researchers also found that the effects of insomnia are enhanced in carriers of the APOE-ε4 genetic variant—the one that confers a higher risk of Alzheimer’s. “The conclusion is that, although the magnitude of the effect is small, this study provides evidence that there is a link between insomnia and the risk of Alzheimer’s: people with insomnia reflect changes linked to this disease,” concludes Grau.
In line with the study by the Pasqual Maragall Foundation, Swedish researchers have discovered that, after subjecting healthy young men to a sleepless night, blood levels of the TAU protein —an Alzheimer’s biomarker— are higher. The accumulation of this protein, which is responsible for stabilizing and helping to assemble the skeleton of neurons, is one of the biological signals that appear in the brain of people with Alzheimer’s. Tau is, together with beta-amyloid protein, the alert for neurological damage caused by this degenerative disease.
The Swedish study, published in the scientific journal Neurology, also brought together 15 healthy men with an average age of 22 and no sleep disorders. In a first phase, they were allowed to sleep normally for two nights; in the second part of the investigation, they were allowed to get a good night’s sleep and were deprived of sleep on the second. Tau levels in the blood increased by 17% after that night of lack of sleep compared to 2% in a normal night’s sleep. “Our study suggests that acute sleep loss results in increased blood tau levels. These changes provide further evidence that sleep loss can have detrimental effects on brain health, even in younger individuals,” they conclude. the researchers.
The finding is in line with other studies that have already found, in cerebrospinal fluid, an increase in tau and beta-amyloid proteins during acute sleep deprivation. A study published in Annals of Neurology in 2018 already pointed out that sleep deprivation increased amyloid beta levels between 25% and 30%.
“Insomnia is a risk factor. It does not cause, per seAlzheimer’s, but it increases the risk of dementia”, values the neurologist Albert Lleó
“Insomnia is a risk factor. It does not cause, per se, Alzheimer’s, but increases the risk of dementia. But the mechanisms remain unclear. What we know is that during the night, the brain takes the opportunity to eliminate waste proteins”, values Albert Lleó, director of the Memory Unit of the Neurology Service of the Sant Pau Hospital in Barcelona. Regarding the two published studies, in which Lleó has not participated, the neurologist believes that both “demonstrate that insomnia produces biological alterations, one at the level of brain structure and the other through blood tests”. However, the doctor clarifies that, “for these alterations to be relevant , sleep disorders have to last for many years and it also depends on their intensity”. Lleó’s team has participated in studies where they found that sleep disturbance is very common in people with Down syndrome, a group that is especially vulnerable to Alzheimer’s: 70% of them suffer from this ailment at the age of 60.
The scientific community knows that mechanisms are activated during sleep that help clean up the garbage from brain metabolism, but that during wakefulness the production of beta-amyloid and tau increases. However, the researchers agree that many questions remain to be answered, such as the real level of influence of sleep disorders, the role of inflammation in the insomnia-Alzheimer association, and the direct action of these proteins. “Experience tells us that accumulating tau in the brain is not good. In neurological disease, we interpret the accumulation of tau as neuronal damage. The study published in Neurology it’s with 20-year-olds and we don’t know what that tau means. We still need to understand the physiology of these proteins and the changes they experience during sleep-wake,” says Grau, whose study was supported by La Caixa.