What is Alzheimer’s Disease?
Alzheimer’s disease is a neurological disorder in which we see cortical atrophy (shrinkage of the cells within the cortex of the brain) occurring within the brain. Alzheimer’s can be both genetically inherited (around 10%-15% of cases), or sporadic/not inherited (85%-90% of cases), and in fact the greatest risk factor of the later is simply the advancement of age[1].
The symptoms of Alzheimer’s disease are linked to the areas within the brain which are affected. For example when the hippocampus shrinks we observe memory loss as this is the area of the brain associated with forming new memories. Other symptoms include, problems with reading, a lack of attention and poor vision to name a few. However, the overall devastating impact is brain-wide cognitive impairment.
The image below displays the differences between a healthy individual and a patient with Alzheimer’s disease. The right hand side of the image shows a brain with Alzheimer’s disease (AD). We see cortical thinning, resulting in a loss of information processing within the brain, as well as a prominent increase in the size of the brains ventricles (the areas of the brain full of cerebral spinal fluid). Most notably, enlargement of the posterior ventricles is very apparent since they now occupy the space previously taken up by the hippocampus which has shrunk away.
Image adapted from: Stacy Jannis – an image for the Alzheimer’s Association[2]
A Little History
The first recorded patient with AD was Auguste Deter. Dialogues of her conversations with Alzheimer exposed difficulties she had in remembering important parts of her life. Following on from this, observations made from microscope images of slices of her brain led to the discovery of the hallmark pathological structures observed in an AD patient. The first are called neurofibrillary tangles which are made up of a protein called Tau, and the second are plaques made up of the beta-amyloid protein.
Image from: https://www.brightfocus.org/alzheimers-disease/infographic/amyloid-plaques-and-neurofibrillary-tangles
But what does the formation of these structures mean for the brain? Well when Amyloid plaques form near to neurons it actually will cause the neurons to die, it is thought that this occurs due to them setting off an immune response[3]. On the other hand, Neurofibrillary tangles form within neurons, affecting the ability of the neuron to produce and breakdown proteins, this ultimately leads to death[3].
How does AD relate to global warming?
Although research into the effects of global warming on the human body is still lacking, in recent years this area is gaining more and more interest. In 2017 Culqui et al conducted a study in Madrid assessing the links between Alzheimer’s disease hospital admissions and environmental factors (specifically air pollution and temperature). Alarmingly, it was shown that when temperature rose at least 1.33°C above the heatwave threshold of 34°C, a huge 23.1% increase in emergency related Alzheimer’s disease hospital admission occurred[4]. These findings highlight the dramatic effect that the climate can have on our health. Not only is this worrying for us all individually, but as global warming continues, it indicates that healthcare systems worldwide might come under more and more pressure. The need to reverse this trend is becoming ever more important!