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Sleep apnea treatment may improve memory in people with cognitive decline: The Tribune India

Sydney, May 21

There is growing recognition of the important role sleep plays in our brain health. A growing body of evidence suggests that disturbed sleep may increase the risk of developing dementia.

Colleagues from the University of Sydney and I have published a new study showing that treating sleep apnea in older people with mild cognitive impairment can improve memory, but not other areas of cognition, short term.

As there is currently no treatment or cure for dementia, increasing efforts have focused on developing new approaches to slow its progression. Mild cognitive impairment is the stage between the cognitive decline expected of normal aging and the more severe decline of dementia.

In the case of mild cognitive impairment, the individual, family, and friends notice cognitive changes, but the individual can still carry out daily activities. Mild cognitive impairment is associated with an increased risk of developing dementia in later years.

Researchers believe this is the optimal time to intervene to help prevent a future diagnosis of dementia. It is therefore important to find new ways to slow cognitive decline in people with mild cognitive impairment.

Why is sleep important for our brain health?

Sleep optimizes our brain’s ability to stabilize and consolidate newly learned information and memories. These processes can occur in all stages of sleep, with deep sleep (also called stage 3 or restorative sleep) playing a key role.

We also now know that the glymphatic system, or the waste management system of the brain, is very active during sleep, especially during deep sleep. This process allows the waste products, including toxins, that our brain has accumulated during the day to be cleansed.

Toxins in the brain include beta-amyloid, one of the key proteins in the development of Alzheimer’s disease. Disrupted sleep could disrupt this cleansing process and lead to greater buildup of beta-amyloid in the brain.

The important role of sleep in these vital processes has led to research whether sleep disturbances, including sleep disorders, may be associated with changes in our cognition as we age and a possible link to the development of dementia.

What is sleep apnea?

Sleep apnea is estimated to affect 1 billion people worldwide. In Australia, 5-10% of adults are diagnosed with the disease. Sleep apnea causes the throat (also called the upper airway) to close completely (apnea) or partially (hypopnea) during sleep.

These closures or obstructions can last anywhere from ten seconds to a minute and can cause low blood oxygen levels. To start breathing again, a brief awakening occurs without the individual being aware of it.

In someone with severe sleep apnea, this process can occur 30 or more times per hour, causing very fragmented sleep. People with sleep apnea may snore, toss and turn, and others may notice that they stop breathing, choke or suffocate while sleeping.

These repeated sleep disruptions can lead to drowsiness and reduced alertness during the day, which in some people leads to difficulty performing tasks.

Does sleep apnea increase our risk of dementia?

Sleep fragmentation, along with nighttime blood oxygen dips, is a double whammy in dementia risk. Studies have shown that sleep apnea is associated with a 26% increase in the development of cognitive impairment, as well as higher amounts of beta-amyloid in the brain.

However, it is unclear whether treating sleep apnea could reduce this risk.

The standard treatment for sleep apnea is continuous positive airway pressure therapy, commonly known as CPAP, in which a mask connected to a pump continuously blows air into the upper airways, keeping them open.

When the machine is in use, it prevents the airway from closing. It is not known whether treating sleep apnea will reduce the risk of dementia. Our new research, however, shows that CPAP may benefit short-term memory.

Our study aimed to understand whether treating older people with both sleep apnea and mild cognitive impairment could improve thinking skills and short-term memory.

The trial assessed the effect of CPAP treatment on memory and thinking skills compared to no treatment. This was a crossover study, meaning all participants had both CPAP and no treatment during the trial, but at different times. Some had CPAP first, then switched.

The others initially received no treatment, then switched. Trained staff helped participants get used to the therapy, and after using it for three months, participants underwent a series of cognitive tests.

Researchers found that compared to untreated sleep apnea, thinking skills were not improved with CPAP, while some memory improvements were seen. This suggests that treating sleep apnea could potentially improve short-term outcomes, but whether it would impact long-term cognitive decline is unclear.

A previous study suggested that CPAP may slow cognitive changes over a year in older adults with mild cognitive impairment and sleep apnea. However, longer studies are needed before we can say what the long-term effects look like. (The Conversation, by Camilla Hoyos, Research Fellow, University of Sydney)


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