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Link Between Dementia and Your Bedtime

While it is pretty normal to have trouble sleeping once in a while, but if you find yourself unable to sleep most of the time, it could be that it is an early sign of dementia. The symptoms of dementia can show up several years before you actually get diagnosed with any kind of dementia, usually Alzheimer’s disease, which is the most common form of dementia. Even though experts are not sure about which comes first, whether you experience sleeping problems before the signs of dementia, but there is no doubt that there is a connection between the two, primarily related to the number of hours you spend in bed. Here’s everything you need to know about the link between dementia and your bedtime.

Link Between Dementia And Your Bedtime

New research has shown that there is a link between the time you spend in bed and your bedtime to the risk of dementia. Alzheimer’s disease, the most common form of dementia, is known to be one of the top ten leading causes of death in the United States. In fact, globally, the risk of dying due to Alzheimer’s disease has nearly tripled in the last 30 years.(12) The research study found that people between the ages of 60 to 74 years were most affected. Before this, other studies had also highlighted the association between sleep quality and dementia and memory.

We all know that sleep has a direct impact on our physical and mental health. Sleep is also linked to many health conditions, including heart disease, depression, obesity, and even heart attack and stroke.(3456)

New research published recently in September 2022 in the Journal of the American Geriatrics Society provided new insights into the role of sleep and dementia.(7) Researchers from the UK, Sweden, and China collaborated to study the sleep data of 1982 Chinese participants. The individuals in the study had an average age of 70 years, and none of them showed any symptoms of dementia at the beginning of the study.

After 3.7 years later, it was found that 97 participants, roughly five percent, had been diagnosed with dementia based on the criteria mentioned in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). The participants who were majorly affected were between the ages of 60 to 74 years. Men were also found to be at a greater risk, which went against what other dementia studies and researchers have seen earlier.

One of the research authors said that while in most studies, women have been found to have nearly two times the risk of dementia as compared to men, but in this study, it was unusual that the research team found the opposite to be true.

What Did The Study Discover?

The study discovered that the longer time participants spent in bed, the higher was the risk of dementia. Those participants who stayed in bed for over eight hours were much more likely to experience a cognitive decline when they underwent a Mini-Mental State Examination (MMSE), which is a diagnostic test used for measuring cognitive decline or impairment.(89)

As people get older, many start to spend more time in bed because there is a fragmentation of the sleep states that takes place. This means that some people are not able to achieve the same type of physically refreshing sleep, which is usually the third or fourth stage of sleep, as they did when they were younger. Due to this, it is possible that older people with poorer sleep quality start needing more sleep time to feel refreshed.

However, poor quality of sleep is not the only factor at play here. Older adults are known to be at a higher risk of depression as well, which again makes sleeping difficult.(10) At the same time, there are many other health conditions like diabetes or heart disease, as well as the medications taken for them, that increases fatigue and the need for sleep.

The research team also stressed on the bedtime of the participants. Bedtime was found to be an essential contributing factor, with early-mid evening hours appearing to be the riskiest. The study concluded that every one-hour increase in bedtime before 10 pm was linked with a 25 percent higher risk of dementia. The researchers claimed that earlier bedtimes were also possibly caused by the impaired circadian rhythm in the individuals.

It is known that certain parts of the brain that are responsible for the management of our sleeping cycle begin to change as we get older. This affects our circadian rhythm cycles. Other age-related factors, such as having to go to the bathroom more frequently during the night, also have an impact on getting a good night’s sleep. This often leads to accumulative sleep deprivation, which causes a change in the structure of the brain that controls the circadian cycles.(11121314)

Another factor that could have an influence is known as brain fatigue. People with early stages of dementia or cognitive decline may experience earlier brain fatigue during the day. This may make them want to go to bed earlier. This effect is known as ‘sundowning,’ and it is a common phenomenon that occurs in older people who are prone to dementia. This causes them to become disoriented and confused towards the evening.(1516)

Are There Any Limitations To This Study?

One of the major limitations of this research study is that time spent in bed does not precisely reflect the time that the participant spent being asleep. Sleep duration is one of the most essential factors in the risk of dementia and cognitive health. The longer time spent in bed could be an indication that there is an underlying sleep condition, such as insomnia, which might be making the situation worse and having an impact on the results of the study.

This was highlighted by a recent Canadian study which showed that people with insomnia are at a greater risk of memory loss and cognitive decline.(17)

At the same time, neither does the time spent in bed consider the quality of the participant’s sleep. This is also an important factor that determines the risk for dementia and cognitive decline. For example, not getting a good quality of deep sleep at night can dramatically impact a person’s memory.

Impact of Sleep on Memory

One of the key signs of dementia is memory loss. Quality sleep is required for the proper functioning of all types of memory during our lifetime. If you remain in a state of slumber, it has an impact on your memory. The first impact takes place on the processing and storing of memories.

Short-term memory is originally stored in the part of the brain known as the hippocampus when it arrives in the brain. The hippocampus is the area where data is stored for short-term use and recollection. And when we sleep, this information from the hippocampus is passed along to the higher cortical structures of the brain. Here, this short-term information is converted into long-term memory, and the information is further integrated with your past memories.(1819) This process is known as memory reconsolidation, and it is dramatically affected if you don’t get good quality REM sleep or if you are sleeping for a shorter duration than what is required.

The second impact happens when the brain is unable to remove the harmful toxins. Over a period of time, this accumulation of harmful toxins has an impact on your memory. During the day, when the brain remains active, it produces a lot of inflammatory waste products or reactive oxygen species. And at night, when you go to sleep, the brain recovers from the entire day’s work, it detoxifies and removes a lot of this inflammatory waste product. However, this action typically takes place when you are in deep and REM sleep. An accumulation of such toxins puts a lot of stress on the brain and prevents it from accomplishing the process of memory reconsolidation.

This is why sleep quantity and sleep quality are both important factors that affect your memory and brain.(2021)

Signs and Symptoms of Dementia

This study looked at the onset of dementia in older people, that too during the time of life when the symptoms of this illness are most likely to become apparent. The many types of dementias, especially Alzheimer’s disease, usually become apparent with symptoms when people reach their 60s, though, of course, there are cases where early onset occurs in the 40s or 50s itself.(22)

Dementia is actually an umbrella term that is used to describe a group of diseases that cause progressive changes in the structure and function of the brain.(2324)

Some of the common signs and symptoms of dementia include:

  • Persistent and pervasive challenges with cognition, memory, language, and everyday tasks
  • Inability to pay attention
  • Loss of concentration
  • Loss of language skills
  • Decrease in visual perception
  • Impairment in judgment and reasoning skills
  • Loss of problem-solving skills

There have been many studies carried out on the various risk factors of dementia. The particular study discussed here revealed that sleep is also a major risk factor for dementia. However, sleep is not the only risk factor that increases the risk for dementia. There are many other causes of dementia, and it is also believed that it is a combination of factors that contribute to the development and advancement of the disease.(25)

Medical experts believe that dementia may be caused by:(26)

  • Genetics
  • Untreated and prolonged depression.
  • Inflammation that is caused by poor diet, poor sleep, lack of exercise, high cholesterol, unmanaged diabetes, and other unhealthy lifestyle habits.
  • Development of abnormal ‘tau’ proteins in the brain.
  • An inability of the brain to use insulin properly.


Sleep has been associated with dementia for a long time. Poor quality of sleep is known to increase the risk of dementia. At the same time, those individuals who already have dementia often find themselves struggling to get a good night’s sleep. This study did not look at some of the vital aspects of sleep, including the quality of sleep. However, the study did highlight the association between the time spent in bed, dementia, and bedtime. While more research is still needed to see how exactly time spent in bed and a person’s bedtime influences the risk of dementia onset, but the findings of this study does suggest that it is essential to monitor the cognitive function of older adults who are spending more extended time in bed and also have earlier bedtimes.


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Sheetal DeCaria, M.D.
Sheetal DeCaria, M.D.
Written, Edited or Reviewed By: Sheetal DeCaria, M.D. This article does not provide medical advice. See disclaimer
Last Modified On:November 20, 2022

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