Sleep disorders are very common in the elderly and can substantially reduce their quality of life. According to research published in the prestigious journal Nature Neurosciences, this decrease in sleep quality would also contribute to the decline in memory that often accompanies aging.
As the saying goes, “the night brings advice”, and sleep is one of the daily activities whose positive impact on health is the most underestimated. Getting enough sleep is not a “waste of time”, as some think, but rather an essential moment to regenerate the body’s energy reserves, stabilize the emotions and ensure psychic balance.
In addition to this “restorative” role, sleep also plays a key role in learning. For example, several studies have shown that the slow (delta) brain waves generated during deep sleep help transfer memories stored in the short term in the hippocampus to the prefrontal cortex, where they will be stored in the longer term. The old saying “the night brings advice” therefore truly has a biochemical and neurological basis!
Sleep problems as you age
Like all organs in the body, the brain undergoes many transformations as we age, including a gradual loss of neurons that can lead to a decrease in brain capacity. Perhaps the most common is the decline in cognitive functions, particularly the deterioration of memory, but there is also a noticeable decrease in the activity of the slow brain waves responsible for deep sleep.
Many elderly people actually have difficulty falling asleep and sleeping normally, their sleep being fragile and marked by frequent awakenings. Could there be a link between this loss of sleep quality and the decline of cognitive functions?
To answer this question, a team of researchers assessed the memory of 18 young adults in their twenties and 15 adults in their 70s. Before going to bed, the volunteers had to memorize 120 pairs of simple words. Once asleep, their brain activity was recorded using an electroencephalogram (EEG). After a full night’s sleep, the researchers asked the participants to list the words they remembered, while the activity of their brain areas was analyzed in parallel by magnetic resonance.
The researchers first observed that older people did less well than younger people on the memory test, which confirms the role of aging in the reduction of memory capacities.
More interestingly, they noticed that these memory problems were closely correlated with the quality of sleep: people who showed a marked reduction in the slow brain waves typical of deep sleep were those with the most impaired memory.
This close relationship between sleep and memory is explained by the loss of nerve cells in the frontal lobe of the elderly: since the slow waves of deep sleep are generated by this region of the brain, the deterioration of these neurons prevents the transfer of information and its longer-term storage.
Better sleep: less coffee, alcohol and heavy meals
Several aspects of lifestyle, however, can help maintain quality sleep, even at older ages.
Older people who lead active lifestyles, such as regular physical exercise such as walking, have fewer sleep problems than those who are sedentary. Reducing caffeine or alcohol intake and eliminating heavy late-night meals are also effective strategies for better sleep.
BA Mander et al. “Prefrontal atrophy, disrupted NREM slow waves and impaired hippocampal-dependent memory in aging”. Nature Neurosciences.