Neurodegenerative conditions are predicted by the World Health Organisation (WHO) to become the world’s leading cause of death by 2040. This class of disease constitutes a group of progressively debilitating conditions with unique disease-specific profiles, characterised by the selective loss of distinctive neuronal groups.
What is dementia?
Neurodegenerative dementias represent a class of pathologies that have varying degrees of, but unarguably, the progressive decline in cognitive functions such that there is interference in an individual’s ability to perform everyday duties, impacting on their social function and/or their capacity to perform usual occupational tasks.
Types of dementia
The most common forms of dementia include Alzheimer’s disease (AD), Lewy body dementia (DLB), frontotemporal dementia (FTD) and vascular dementia. Both AD and DLB continue to be the leading cause of degenerative dementia in the elderly population (Figure 1).
Figure 1 – Dementia subtypes and prevalence
Representative data from the Alzheimer’s society’s (UK) envisaged proportions of the subtypes of dementia and their prevalence in the UK alone. Adapted from (https://www.alzheimers.org.uk/info/20091/position_statements/93/demography), published September 2014.
Dementia has emerged as an epidemic with aging being the predominant risk factor. By 2050, the number of people aged ≥60 years will have increased by 1.25 billion, accounting for approximately 22% of the total global population, with 79% living in less developed regions. Whilst the observed and projected increase in the number of people affected by dementia has largely been explained by the increase in population longevity, specifically in the developing world, dementia per seis not a natural part of the aging process.
Those affected by neurodegenerative dementias are principally aged 65 years and over with early-onset dementia accounting for only 2-5% of all cases, furthermore the prevalence nearly doubles with every additional 5 years of age following the age of 65 underscoring an increase in an age-related risk of developing neurodegeneration, in parallel with an increase in longevity.
In 2015 WHO reported 47.5 million people were afflicted worldwide by dementia, increasing from 35.6 million people in 2012 (WHO April 2012) and cases are predicted to rise by 7.7 million each year. It has been forecast that by 2050 the worldwide prevalence of dementia will reach 137.5 million. In the UK alone, 850,000 people are affected, this bestows a substantial burden on the economy with the cost of health care in the region of £26 billion, annually.
The broad-spectrum of dementia produces a gender bias with a predisposition towards females, 61% of dementia cases are seen in the female population when compared to 39% of males. This is a consistent observation that could be explained by the protracted longevity in females when compared to males.
Global distribution of dementia
A systematic review contemplates the global prevalence of dementia and identifies a higher incidence in Latin-America and lowest in Sub-Saharan Africa with the greater proportion of dementia cases, being affiliated with low-middle range incomes. To corroborate this, more recent population-based studies on “high-income” countries have contradicted previous projections regarding dementia prevalence, indicating a decline in the age-associated risk of dementia. This has been attributed to various factors, largely surrounding the fact that higher levels of education and advances in treatment and diagnostics may lead to the early intervention of dementia indicators; these include cardiovascular risk factors such as obesity and diabetes. A recent UK based study on dementia has reported a 20% decrease in dementia incidence over the last two decades in males. If the previous projections are proving variable, then it is possible that the predicted figures may be regionally modulated in accordance with the scope of social health care support available and attainable by the general population.
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