According to WHO, about 50 million people are experiencing dementia around the globe. Approximately 10 million new cases are reported each year. The global population battling dementia at any one time ranges between five to eight percent. These stats present a gory picture of the dementia crisis that has beset us. In this blog, we are discussing how sleeping less makes us more susceptible to Dementia.
Dementia is a neurological and long-term disease. It takes over our brain in gradual steps. It has many subtypes, with the most common one called Alzheimer’s disease. Alzheimer’s disease causes 60-80% of all dementia cases. Sometimes, a patient can have two different dementias at the same time. This condition is named mixed dementia.
The bad news that the disease has no known cure. One of its main symptoms is aging.
What are the findings of the study?
Research published in Nature Communication has found a correlation between the amount of sleep one gets in middle and old age with the chance of getting dementia.
The data for the research was collected from the people who have been a part of the Whitehall II study. The Whitehall studies were cohort in which the lifespans of individual Londoners were analyzed for health-related issues. The first study began in 1967, followed by Whitehall II, which started in 1985.
A group of French researchers used a sample of 7959 individuals from the Whitehall II study. As the data on these individuals were kept since 1985, it was easy to dissect links, if any, between dementia and their sleeping habits. It was found that there was a 30 percent greater risk of dementia among individuals who were getting shorter spans of sleep.
A total of 521 cases of dementia were found among the total sample. These were the people who were continuously getting only six hours of sleep throughout their 50s and 60s.
Moreover, individuals who were sleeping for a normal duration of seven hours were less likely to get dementia. The results were consistent even after the researchers controlled for other dementia risk factors such as smoking/alcohol use, cholesterol, mild cognitive impairment, diabetes, cardiometabolic problems, mental health issues, hypertension, etc.
How is research different from other studies?
This research has a crucial edge over plenty of other researches conducted on the same topic. Unlike other studies conducted, this research has a follow-up period of 25 years as people with dementia show changes/symptoms over 20 years. Therefore, a study with a long follow-up period was needed. This was important to give some conclusive insight into links between the amount of sleep one gets and dementia.
Another peculiar point in this study was that this one did not find any evidence for an association between sleeping for prolonged durations and dementia compared to previous studies. The result of the study remained consistent when calculated for men and women.
Dementia is a blanket term
Dementia is a syndrome. It displays a recognizable pattern of symptoms/signs which are used to identify it. Doctors have not yet found any diagnosis for dementia. While Alzheimer’s disease is a common cause of dementia but it is still a different disease. At the same time, both Alzheimer’s and dementia have a lot of common symptoms.
What is Alzheimer’s disease?
Alzheimer’s is a neurodivergent and gradually advancing brain disorder. The disease, a common cause of dementia, was discovered by a German Psychiatrist Dr. Alois Alzheimer. Dr. Alois first discovered this disease in 1901 when he saw that a patient showed some strange symptoms.
After the patient died, Dr. Alois performed an autopsy on her dead body. Unsurprisingly, he found some irregularities in the structure of her brain. She had misfolded proteins in her brain tissue. There were two different patches of tissues in parts of her brain–plaques and tangles.
Plaques and Tangles
Plaques and Tangles destroy our brains’ nerve cells. Among both, plaques are insolvable deposits of a protein called amyloid-beta or a-beta. This protein is formed after its parent protein, called amyloid precursor protein, and is scissored by enzymes. After its formation, a-beta started misfolding and clumping together, forming patches of plaque. These clumps block the flow of signals between neurons resulting in blockage of communication.
Another protein that destroys nerve cells is called Tau–a component of tangles. A healthy neuron carries food molecules on its axons in segmented form. The tau proteins stabilize the segments, but in Alzheimer’s disease, tau proteins undergo degeneration and split apart from the microtubules. These tau proteins tangle together, forming clumps that result in the death of neurons.
Tau proteins can also spread to healthy neurons across synapses (a part where two neurons are connected). After reaching normal neurons, they make other normal functioning tau proteins and start misfolding. Thus, the disease starts spreading all over the brain.
How can sleep help in reducing the risk for dementia?
Lack of sleep is a symptom of dementia, yet it helps remove the waste materials from our brain. Removal of excess waste can decrease the chances of getting dementia. Research has shown that a sleep loss of even a single night can increase tau and beta-amyloid proteins in our brains, thus increasing our chances of getting Alzheimer’s disease.
Sleep is really important to clear up the proteins and to put a check on their growth. When we are sleeping, our bodies flush out all the neuro-garbage accumulated in our neurons and brain cells. Also, research has shown that poor sleep quality can cause the destruction frontal cortex of our brain. These findings were associated with people over 60 years of age.
Sleep disturbances have also been linked with amyloidosis – the process by which amyloids break up and clump together. Breaking up proteins like amyloids is a natural process that occurs as we age. However, the process can escalate if we do not get enough sleep. Moreover, researchers also agree that sleep disturbances in old age can be potential signs of neurodegenerative diseases, and we should be on the lookout for them.
Besides, the relationship between sleeping and developing dementia is bi-directional. This means that dementia causes lack of sleep, but lack of sleep can, in turn, exacerbate the disease. If we do not get enough sleep in the earlier years of our life, we may get dementia later on.
Another theory for an increase in the brain-damaging proteins like amyloid is that the longer we stay awake, the longer neurons remain active. As a result, more amyloid and tau are produced. The study published in Nature Communications has also stipulated that people who have shifted their sleeping duration from short (six hours) to normal (seven hours) are more likely to develop dementia.
Limitations of the study
A study published in Harvard Women’s Health Watch found that sleeping for a small and long duration was linked with cognitive decline. The researchers of this Harvard study said that women who slept for six or fewer hours a day have a 36 percent increase in their cognitive decline. Similarly, women who slept for eight hours or longer were found to develop a 35 percent increase in their cognitive decline.
The new research, however, does not address these findings. Another shortcoming of the Nature study was that most of the responses were self-reported. So, some skepticism about how reliable a person’s report of their sleeping routine might be in some cases, where participants used accelerometers to measure their sleep duration. However, these reports only came towards the ending years of the study.
Pre-dementia symptoms for diseases like Alzheimer’s develop over almost two decades. Since sleep deprivation is also a symptom of dementia, the researchers are unsure whether lack of sleep affects dementia or can cause the disease by itself. This has brought the researchers to the classic chicken and egg problem.
There is still a lot that we do not know about sleep and its possible ramifications for our brain. Numerous studies have putatively shown that sleeping can remove the excess proteins in our brain. The same proteins, if left untouched, can accumulate and destroy our nerve cells. This can lead to the formation of neurodegenerative diseases like dementia.
The study does not talk about whether sleeping less causes dementia or is it just a symptom of dementia. The curve for dementia and sleep is a U-shaped curve. So, sleeping too much can also cause dementia. Both ends of the spectrum can have serious consequences.
Perhaps, with the uncovering of new research and evidence, we will conclude a possible connection between sleep deprivation and dementia. Till then, we have to deal with studies like this one with a grain of doubt. As Dr. Séverine Sabia, a co-author of the study, told the Guardian, “I cannot tell you that sleep duration is a cause of dementia, but it may contribute to its development.”