Eyes, Sleep and the Aging Population

Image Credit: U.S. Army graphic

Signs of Alzheimer’s disease begin slowly, Lillian Loescher investigates this insidious phenomenon

Whether it be your grandfather, a neighbour or a close friend of your family everyone seems to know or know of someone who has Alzheimer’s disease. Statistically, about 2 out of every 300 people are currently diagnosed with Alzheimer’s disease, this comes out to be 50 million individuals globally, and there are 10 million new cases every single year. Hallmarked by a decline in cognitive abilities over time, a diagnosis of Alzheimer’s disease is not something anyone wants this holiday season.

In the past decade sophisticated positron emission tomography (PET) scans that use tau-specific tracers have been used for clinical diagnosis as well as for the tracking of disease progression. Tau proteins are present in healthy individuals as well as individuals with Alzheimer’s disease. The difference is that when an individual has Alzheimer’s disease their Tau proteins no longer function the way that they are meant to, which is to help stabilize important structures in the brain called microtubules.

These microtubules respond to mental events and some scientists believe that the quantum vibrations within these microtubules in the brain are responsible for consciousness. In healthy individuals Tau proteins stick to microtubules. But when an individual has Alzheimer’s disease these Tau proteins detach from microtubules and begin to attach to each other. This results in large Tau tangles, which inevitably disrupt the communication between different regions in the brain.

Tau accumulation in the locus coeruleus and cell death within the locus coeruleus begins very early and is preceded by any noticeable symptoms of cognitive impairment, this is called preclinical Alzheimer’s disease. Within the brainstem, a properly functioning locus coeruleus is critical for mediating stress responses in the body as well as modulating memory and attention. How an individual’s locus coeruleus functions can be partially detected by how much their eyes dilate during cognitive tasks, such as memorizing flashcards or reading a book. The harder the cognitive task, the greater the pupil dilation.

A study published in the September 2019 issue of The Neurobiology of Aging, scientists at the University of California San Diego School of Medicine explored this pupil dilation phenomenon. The study included men between the ages of 56 and 66 some of whom had genetic predispositions to Alzheimer’s disease and exhibited mild cognitive impairment as well as a set of men who were cognitively normal. The scientists found that the individuals with mild cognitive impairment, which often precedes Alzheimer’s disease, had larger pupil dilation during cognitive tasks as compared to the cognitively normal group. This indicates that early detection of Alzheimer’s disease may be seen with a simple eye screening. The scientists at the University of California San Diego School of Medicine have shown a proof of concept study that could save patients and their families thousands of euros.

The Alzheimer’s Society of Ireland had an income of 19.4 million euros in 2018 and has spent over 90% of that income on direct care provision for those with the disease. This includes Day Care, Home Care, Respite, and Information and Advisory Services. The left-over funds, which total between 1% and 9% of their income in 2018 (between 194,000 euro and 1.75 million euro) was used for governance, advocacy, research and fundraising costs. Thus, no matter which way one looks at it, the costs associated with living with Alzheimer’s disease far outweigh the funding that is given towards research on the disease. It does not take a neurologist to understand the negative feedback loop that this causes. Therefore, early detection of the condition is paramount to breaking this cycle.

In an article published by JAMA Neurology in March 2011 researchers from the Washington University School of Medicine in St. Louis found that sleep quality is an indicator of preclinical Alzheimer’s disease as well. The scientists took 145 individuals between the ages of 45 and 75 and looked at samples of each of their spinal fluids for markers of preclinical Alzheimer’s disease.

They then analysed each participants sleep quality over a period of 2 weeks. The scientists cited that there is a potential relationship that goes both directions, meaning preclinical Alzheimer’s disease can cause poorer sleep quality and poorer sleep quality can contribute to the development of preclinical Alzheimer’s disease. In the end the study found that those with the worst sleep quality where more than 5 times more likely to have preclinical Alzheimer’s disease.

At a different date, scientists at Washington University School of Medicine found that preclinical Alzheimer’s is associated with abnormal mood states, including depression. Meaning adults who exhibit clinical symptoms of depression are more likely to have preclinical Alzheimer’s disease compared to adults that do not have depression. A study published in JAMA Psychiatry further emphasises this stating that within groups of individuals with preclinical Alzheimer’s disease, “those with elevated anxiety symptoms had a greater decrease in cognitive domains during a 4½-year period than older adults [who also have preclinical Alzheimer’s disease] with non-elevated anxiety symptoms”.

With links to eye pupil dilation, anxiety, depression and sleep quality, preclinical Alzheimer’s begins years or even decades before any cognitive decline. The evidence supporting clear and noticeable symptoms of preclinical Alzheimer’s disease is increasing. Many of these symptoms mask as other illnesses to start with, but as time goes on become part of a common disease shared by 10% of the population that is 65 years or older.

It should be kept in mind that these are the current statistics, and research into preventative measures are plentiful. Researchers at Waterford Institute of Technology and Cambridge University have found that individuals who took special fish oil compounds significantly slowed their onset of Alzheimer’s disease. This is touted as “one of the most important medical advancements of the century”. In addition, it appears that moderate alcohol intake, not smoking, eating a well-balanced diet, keeping fit and remaining mentally active all help to protect against the onset of Alzheimer’s disease.