Alzheimer's Disease - Can its threat be quelled before it becomes evident?

Alzheimer's Disease (AD) is the bane of old age. Approximately 10% of all persons over the age of 70 have significant memory loss, and in more than half the cause is AD. Dementia in AD is slowly progressive. The typical duration of AD is 8-10 years, but the course can range from 1 to 25 years. 

Memory loss is the most striking feature of AD. Language and visuospatial deficits occur later. Once the memory loss falls below 1.5 standard deviations from normal on standardised memory tasks, the disease is defined as Mild Cognitive Impairment (MCI). Approximately 50% of MCI individuals will progress to AD within 5 years. Morbidity associated with AD affects not only the patients, but also the family. Caregiver "burnout" is common and it itself worsens the prognosis of the affected. 

The characterestic pathologic findings in AD are neuritic plaques containing a central Aβ amyloid and neurofibrillary tangles (NFTs) which represent abnormally phosphorylated tau protein. There is diffuse atrophy of cortex with secondary enlargement of the ventricular system. In particular, hippocampus, temporal cortex and nucleus basalis of Meynert is affected.

Alzheimer's Disease starts long way back before it becomes evident. Before it becomes noticeable, about 20% of the brain cells would have been dead. 

Shrunken brain of an Alzheimer's patient compared with a healthy one (Courtesy- BBC)

Research on genetic considerations of AD has been one of the major areas of almost all Neuroscientists. A study published in the Lancet Neurology  found out significant differences in the brains of a group of Columbians whose had mutations which are shown to predispose them to AD in the later decades. The cases and controls were both aged 18-26 years and were subjected to a wide variety of investigations, such as structural MRI and fMRI brain imaging, CSF and plasma Aβ1-42  concentrations, etc. Professionals can get the full details from the hyperlink given in the beginning of the paragraph. The study discovered some of the earliest changes to occur in AD, those which occur many years before the plaque deposition. 

Dr. Simon Ridley, head of research at  Alzheimer's Research UK, said :- 

"Although early-onset inherited Alzheimer's is rare and may not entirely represent the more common late-onset form, the findings highlight changes can take place in the brain decades before symptoms show. Mapping what changes happen early in the brain will help scientists to improve detection of the disease and allow potential new treatments to be tested at the right time. New drugs are being developed and tested to stop amyloid from taking hold, but studies like these show that timing could be crucial for whether these drugs are successful."

The study may not entirely put the current diagnostic and management lines of AD into a sudden change, but it is definitely a big step forward along the right direction before finally contemplating the quantum leap.