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Poor sleep has recently been identified as one of the 14 risk factors for developing early cognitive decline by the 2024 report by the Lancet Commission on Dementia Prevention, Intervention and Care. This was a collaboration between the journal, The Lancet, and international experts from several academic and charitable institutions, to create evidence-based recommendations for dementia care. You can read more about this from an earlier article from Dr. Mayer here!

The importance of getting a good night of sleep has long been instilled in the majority of people, and experts are recommending adults to sleep an average of 7-9 hours per night. Yet, most adults are getting only 5.7 hours of sleep per night on average. A lack of sleep, usually considered to be sleeping for less than 6 hours per night, is associated with a higher risk of developing Alzheimer’s disease. Based on this, one may conclude that the more sleep someone gets, the less likely they are to risk developing dementia—but this is not exactly the case either. Scientists have found that getting too much sleep is also associated with a higher risk of developing dementia.

“A lack of sleep, usually considered to be sleeping for less than 6 hours per night, is associated with a higher risk of developing Alzheimer’s disease.”

There is a clear relationship between sleep and dementia, but the dynamic is somewhat complicated. While scientists know that the amount of sleep that an individual gets each night does affect their risk of developing dementia, the relationship is a classic chicken and the egg situation. It could be thought that the lack of sleep leads to changes in the brain that lead to poor cognition and eventually turns into dementia. On the other hand, the cause of sleep disturbances could be from underlying health issues that are known to negatively affect brain health.

Similarly, sleep apnea is one underlying health condition that has been associated with a higher risk level of developing dementia. It is unknown as to whether the disruption of sleep from the condition is what leads to an increased risk of dementia, or if it is the fact that majority of people with this condition have health issues such as being overweight and/or having diabetes, which is also associated with an increased risk of developing dementia. Furthermore, even when someone doesn’t have these associated health issues, sleep apnea may restrict the amount of oxygen the brain is receiving, resulting in increased inflammation and damaged cells.

Sleep is so important for the health of the brain because every night when we are asleep, our brain has the time to clear all the waste that has built up in your brain throughout the day. As we think and go about our day, it is natural for cellular waste to build within the brain. When we sleep, we flush out the waste into our liver and kidneys and from there it is excreted from the body. Part of the waste being rid from the brain during this process is amyloid protein.

Sleep essentially functions as the filter for your brain cells to get rid of the amyloid protein. Amyloid protein buildup in the brain occurs naturally throughout the day, but if it is not cleared during sleep, serious problems may start to develop. The longer we are awake, the less time we allow for the amyloid protein to be cleared from our brain. When abnormal levels of the amyloid protein accumulate, it sticks together and forms plaques in the brain. These plaques are believed to lead to Alzheimer’s disease as they are responsible for disrupting cellular function.

“We all create waste and build up amyloid protein in the brain throughout our day, but if we do not clear it, then that is when more serious problems can start to occur.”

So just how worried should someone be if they’re not able to hit the 6-hour benchmark of sleep each night? Well, Dr. Sudha Seshadri, founding director of the Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases at the University of Texas Health Science Center at San Antonio, states that a lack of sleep alone is likely not enough to cause dementia, however it definitely does increase the risk of development and can even speed up the process of neurodegeneration. While the onset of dementia does not typically affect adults until they are around the age of 65 years old, amyloid plaques can begin to accumulate up to two decades prior. With that said, prioritizing adequate sleep is important starting in your 40s, ideally even earlier.

Clearly a healthy amount of sleep is beneficial to the health of the brain and preventing the onset of dementia. But, like most things, too much of anything is a bad thing. Getting too much sleep is not beneficial either. If someone has a difficult time waking after 9 hours of rest, or they spend hours during the day taking naps, then this may also be an indicator of underlying health problems that may be leading to the future onset of dementia. The need for excess amounts of sleep can be associated with various physical and mental health conditions such as depression, anxiety, loneliness, diabetes, inactive lifestyles etc. Researchers believe that too much sleep likely isn’t the cause of the problem, but rather an underlying symptom of something else.

“If someone has a difficult time waking after 9 hours of rest, or they spend hours during the day taking naps, then this may also be an indicator of underlying health problems that may be leading to the future onset of dementia.”

The areas of the brain that are first impacted by Alzheimer’s disease are responsible for the regulation of sleep and the circadian rhythm. With that said, an impact to one’s sleep routine might be the first indicator of dementia, before more commonly recognized symptoms such as memory problems start to occur. It is important to note that sleep cycles and routines do naturally begin to change with age. Older adults may change their sleeping patterns after retirement, where they find themselves taking more naps or waking up earlier. However, any dramatic changes may be outside the realm of normal sleep changes that come with aging start to occur, then it is a good idea to see a doctor.

Sleep is vital to the health of everyone and at any age, healthy levels of sleep have been shown to be beneficial for the brain. It is important to understand the role sleep plays in optimizing our health, and also the role it can potentially play in signaling a potentially deeper health issue. Maintaining good sleep hygiene and aiming to get 7-9 hours of sleep is a great way to lower the risk of developing dementia, along with optimizing overall health and well-being.