The surprising link between bedtime and dementia

  • Alzheimer’s disease, a common form of dementia, is one of the top ten leading causes of death in the United States.
  • New research indicates that time spent in bed and bedtime may impact dementia risk.
  • People aged 60-74 are the most affected.
  • Previous research has also highlighted the role of sleep quality in memory and dementia..

Sleep can influence physical and mental health and is linked to illnesses ranging from heart disease and stroke to depression and obesity.

And a new study published on September 21 in the Journal of the American Geriatrics Society provided new insights into the role of sleep in dementia.

Researchers in China, Sweden and the UK looked at sleep data from 1,982 Chinese with an average age of 70, none of whom had symptoms of dementia at the start of the study.

An average of 3.7 years later, 97 participants (5%) had been diagnosed with dementia according to the criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV).

Those mainly affected were between the ages of 60 and 74. Men were also at higher risk, which contradicts what many other dementia researchers have already found.

“In most studies, women are known to have twice the risk of dementia than men. It is unusual that this study found otherwise,” said Dr. Alex Dimitriu, dual board certified in psychiatry and sleep medicine and founder of Menlo Park Psychiatry & Sleep Medicine and BrainfoodMD.

The study found that longer time spent in bed (TIB) was associated with a significantly increased risk of dementia. Those who stayed in bed for more than 8 hours were much more likely to show cognitive decline on a Mini Mental State Examination (MMSE) – a test used to measure cognitive impairment.

So why might older people need to spend more time in bed?

“As we age, we see a fragmentation of sleep states,” sleep specialist and clinical psychologist Dr. Michael Breus told Healthline. This means “we don’t seem to be getting the same type of physically restorative sleep (stages 3/4) as when we were younger.”

As such, “people with poor sleep quality may need more sleep time to compensate,” Dimitriu added.

Other factors may also play a role, explained Dr. Carl W. Bazil, PhD, Caitlin Tynan Doyle, professor of neurology at Columbia University College of Physicians and Surgeons.

Depression (for which the elderly are at greatest risk) can make it difficult to sleep, he explained. “But there are also many other medical conditions (such as heart disease or diabetes) and the medications taken for them that can increase fatigue and sleep needs.”

The time at which individuals went to bed has also been highlighted by researchers as a key contributing factor. Early evening hours were considered the riskiest. The research paper stated that “every 1 hour advance to bedtime [before 10 pm] was associated with a 25% increased risk of dementia.

The study authors hypothesized that earlier bedtimes could be driven by a disturbed circadian rhythm.

“The parts of the brain responsible for sleep management begin to change with age. It impacts our circadian rhythm cycles,” said Dr. David Rabin, PhD, neuroscientist, board-certified psychiatrist and co-founder of Apollo Neuro, a wearable stress relief device.

Age-related factors, such as having to use the bathroom more frequently during the night, “also impact our deep, good-quality sleep,” Rabin continued. Cumulative sleep deprivation “leads to a change in brain structures that regulate circadian cycles.”

Other influences could also be at play, Dimitriu said.

“It’s possible that people in the early stages of dementia experience brain fatigue earlier in the day, leading them to want to sleep earlier,” he said. “Sunset is a well-known effect in older people prone to dementia, where they can become confused and disoriented in the evening.”

Limitations of the study to be taken into account

One of the main disadvantages of research is that the TIB does not necessarily reflect the weather. spent sleeping. Sleep duration has been noted by scientists as a crucial factor in cognitive health and dementia risk.

Breus said a longer TIB could indicate an underlying sleep-related issue, such as insomnia, that “could affect this situation and make it worse.”

A recent Canadian study also pointed out that people with insomnia were at a higher risk of memory loss.

Additionally, the BIR does not take into account the quality of a person’s sleep, which is also thought to be important in cognition and dementia. For example, not sleeping deeply enough can have a huge impact on memory (more on that later).

There is one final consideration to keep in mind.

“This study, along with many others like it, are association studies and as such do not show cause and effect,” Bazil explained.

“It is therefore never clear whether the observed association (in this case, short or long periods in bed or time of falling asleep) actually causes dementia, or is indirectly related to it,” he said. added.

A key sign of dementia is memory loss. However, at all stages of life, “we know that quality sleep is necessary for many, if not all, types of memory,” Bazil explained.

So what happens when you are in a state of sleep? When it comes to memory, two main actions occur.

The first is the processing and “storage” of memories.

“Short-term memory is initially stored in the hippocampus when it arrives in the brain, which is the area where information is stored for short-term recall and use,” Rabin explained.

“When we sleep, information from the hippocampus is transmitted to higher cortical structures in the brain, allowing it to become long-term memory and integrate with memories from the past,” he continued.

Rabin revealed that this process is called memory reconsolidation – and is particularly affected by poor REM sleep quality or shorter sleep duration.

Second, sleep is when our brain eliminates harmful toxins that over time can impact memory.

“When the brain is active during the day, it produces a lot of what we call ‘reactive oxygen species,’ or inflammatory waste products,” Rabin said. “When the brain is asleep and able to recover, especially in deep and REM sleep states, [it] detoxifies and eliminates inflammatory waste.

A buildup of toxins ultimately puts additional stress on the brain and prevents it from achieving memory reconsolidation.

“In summary, the quality of sleep, as much as the quantity of sleep, can be important,” Dimitriu said.

This study monitored the onset of dementia in older people – the time in life when its symptoms are most likely to appear.

“Dementias, such as Alzheimer’s disease, often present with symptoms [among people] in your 60s, although an early onset in your 40s or 50s can occur,” Dr. Sandra Petersen, senior vice president of health and wellness at Pegasus Senior Living, told Healthline.

She continued: “Dementia is an ‘umbrella’ term for a group of conditions, of which Alzheimer’s disease is the most common, in which progressive changes occur in the brain.”

Petersen explained that the common signs and symptoms of dementia are:

  • Persistent and pervasive difficulty with memory, cognition, and the ability to perform daily tasks
  • Loss of focus
  • Inability to pay attention
  • Loss of language skills
  • A decrease in visual perception
  • A loss of problem-solving skills
  • Impaired reasoning and judgment

Dementia risk factors

If this new study (among others) reveals that sleep is a risk factor for dementia, it is not the only player involved.

“Researchers have looked at a number of possible causes of dementia,” Petersen said. “We don’t know for sure, but it’s probably a combination of factors that contributes to [its] development and evolution. »

She revealed that scientists hypothesize that dementia may come from:

  • Inflammation – resulting from poor sleep, poor diet, lack of exercise and other unhealthy habits
  • The appearance of abnormal ‘tau’ proteins in the brain
  • Genetic
  • Untreated and prolonged depression
  • The inability of the brain to properly use insulin

Sleep has long been linked to dementia. Poor sleep is thought to increase the risk, while people with dementia often struggle to get a healthy, restful night’s rest.

This study did not explore some critical aspects of sleep, such as quality. However, it does highlight the link between dementia and BIR and bedtime – things the article noted as “poorly understood” and “rarely explored”, respectively.

Further research is needed to determine how BIR and bedtimes may influence the onset of dementia.

But, until then, the study authors said their findings “suggest that cognitive function should be monitored in older adults who report prolonged time in bed and advanced sleep patterns.”

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