We know that several physical health problems, such as cardiovascular issues, have been linked to a lack of sleep. It is also known that sleep disorders can result in or be caused by mental health conditions, especially major depression.
What isn’t so clear to the general population is if there’s a link between sleep and dementia disorders such as Alzheimer’s disease. This article will discuss important aspects of Alzheimer’s disease and then review how sleep may impact this type of dementia.
History of Alzheimer’s disease
The first case of Alzheimer’s disease was identified in 1901 by German psychiatrist Alois Alzheimer in a 50 year old woman he called Auguste D.1 For most of the 20th century, Alzheimer’s disease was reserved as the diagnosis of those between 45 and 65 years of age demonstrating clinical features of dementia. Patients over 65 with dementia were diagnosed as having senile dementia, but this was changed in 1977 to be included as part of Alzheimer’s disease. Alzheimer’s disease is therefore used to describe a specific type of dementia in all ages.
Alzheimer’s disease is the most common type of dementia affecting up to 65 percent of all known cases. In 2015, it was estimated that nearly 30 million people worldwide were living with Alzheimer’s dementia, and the disease resulted in nearly 2 million deaths that year alone.2
In developed countries, Alzheimer’s disease is one of the most financially burdensome diseases.3 In the United States alone, this dementia costs the country nearly $100 billion every year, which makes it the third most expensive disease in this country. As society ages, so will the incidence of Alzheimer’s disease. This illness will therefore, on a yearly basis, end up being more costly to each affected country. Medications used to help reduce some of the symptoms of the dementia may help to decrease the financial costs associated with the disease.
Not only does Alzheimer’s disease place a heavy burden on a country’s financial resources, but it also places a heavy load on the caregivers and the their social structures.4 It has been noted that patients with severe Alzheimer’s disease need daily assistance. Since many do not have the financial means to hire nurses and nursing homes to look after their loved ones, the burden falls to the family members to care for these individuals. Time and time again it’s demonstrated that caring for patients with Alzheimer’s disease can lead to increased stress and anxiety, with subsequent depression, in some family members who support these patients. This is why support groups are available for family members who look after Alzheimer’s patients, and they are urged to make use of the services of these groups.
The cause of Alzheimer’s disease
Alzheimer’s disease is a neurological condition where the nerve cells of the brain are affected. Under certain circumstances, the nerve cells deteriorate gradually over time due to damage inflicted on them. This is referred to as progressive deterioration of the cerebral cortex of the brain. On MRI and CT scans, doctors can actually visualize how atrophied (shrunken) the brain looks because of the loss of these nerve cells in the brain.
The reason why the nerve cells in the brain are affected is due to certain proteins that clump up together and then attach themselves to and damage the brain tissue. The proteins involved here are called beta-amyloid and tau. Normal proteins called APP are found on the surface membrane of the nerve cells, and in Alzheimer’s disease there are enzymatic actions which result in these APP proteins breaking down into smaller fragments. These fragments are the origin of the beta-amyloid proteins.5
Exactly how these beta-amyloid and tau proteins are produced and aggregate to cause Alzheimer’s disease is not clearly understood. The hypothesis is that they clump together and causes plaques and tangles that lead to nerve cell damage and brain atrophy.
The benefit of sleep
Researchers have discovered that sleep helps to consolidates long-term memories in the brain. One excellent article though looks at another benefit of sleep and how the lack of it can result in neurodegenerative disorders.
During sleep, the brain tries to maintain metabolic homeostasis. In other words, the brain tries to balance the fluids in the organ so that proper functioning and activity of the brain can remain constant. It was demonstrated in the study that during sleep, there was a 60 percent increase in the interstitial space (space between the brain and the membranes that covers the organ), and this allowed for an exchange of the fluid in this interstitial space and the cerebrospinal fluid (fluid found around the spinal cord and brain). The researchers called the space where the exchange took place the glymphatic system, and it is mediated by glial cells in the central nervous system.
The major discovery was that exchange between the two fluids increased the rate of clearance of beta-amyloid proteins, which are associated with the development of Alzheimer’s disease. It was therefore discovered that the restorative function of sleep helps to remove potentially neurotoxic proteins that accumulate during the wakeful state of the neurological system.6
It’s clear that Alzheimer’s disease has an enormous financial and social impact. More importantly though, is that the disease can cause severe stress and anxiety which can lead to more severe complications in close family members who look after their loved ones diagnosed with this dementia.
Most believe that beta-amyloid proteins are a the main reason behind the development of Alzheimer’s disease. Since sleep helps to clear out these potentially harmful proteins on a nightly basis, it is quite possible that a good night’s sleep can aid in preventing or reducing the risk of developing Alzheimer’s disease?
Patients who therefore struggle with their sleeping habits seem to be at an increased risk of developing Alzheimer’s disease. It’s important then that individuals with sleeping disorders seek help and are managed appropriately to help reduce this risk.
- Maurer Ulrike; Maurer Konrad (2003).Alzheimer: The Life of a Physician and the Career of a Disease. New York: Columbia University Press. p. 270.
- GBD 2015 Disease and Injury Incidence and Prevalence, Collaborators. (8 October 2016). “Global, regional, and national incidence, prevalence, and years lived with disability for 310 diseases and injuries, 1990–2015: a systematic analysis for the Global Burden of Disease Study 2015.”. Lancet. 388(10053): 1545–1602.
- Economic Considerations in Alzheimer’s Disease. Pharmacotherapy. 1998;18(2 Pt 2):68–73; discussion 79–82.
- 4. Clyburn, L. D., Stones, M. J., Hadjistavropoulos, T., & Tuokko, H. (2000). Predicting caregiver burden and depression in Alzheimer’s disease. Journals of Gerontology Series B: Psychological Sciences and Social Sciences, 55(1), 2.
- Hooper NM. Roles of Proteolysis and Lipid Rafts in the Processing of the Amyloid Precursor Protein and Prion Protein. Biochemical Society Transactions. 2005;33(Pt 2):335–38.
- Lulu Xie, Hongyi Kang1, Qiwu Xu, Michael J. Chen, Yonghong Liao, Meenakshisundaram Thiyagarajan, John O’Donne, Daniel J. Christensen, Charles Nicholson, Jeffrey J. Iliff, Takahiro Takano, Rashid Deane, Maiken Nedergaard (2013). “Sleep Drives Metabolite Clearance from the Adult Brain”. Science.342 (6156): 373–377.