Ageing Flashcards
Introduction
By the year 2020, half the population of the UK will be over 50 years old. As increased age is associated with a decline of cognitive abilities, it is important to understand the effects of ageing properly in order to see if we can hinder the pathological effects that some people currently endure. This essay shall look at typical and pathological ageing in terms of the frontal executive and disconnection hypothesis as well as vascular damage which leads into some types of dementia and will also outline detrimental effects these have on cognition
West (1991) notes that executive function is a primary deficit in ageing.
West (1991) notes that executive function is a primary deficit in ageing. Executive functions (also known as cognitive control and supervisory attentional system) is an umbrella term for the management (regulation, control) of cognitive processes, including working memory, reasoning, task flexibility, and problem solving as well as planning and execution. Executive functions is associated with the frontal lobes and a decline of grey matter in them.
Raz et al (1997) posits that the frontal lobes are selectively affected in ageing
Raz et al (1997) posits that the frontal lobes are selectively affected in ageing. In a cross sectional MRI study on 148 participants, age 18-77; the researchers found that per decade there was 4.9% cognitive decline in the prefrontal cortex (PFC), 4.3% decline in the superior parietal cortex and a 2% decline in the hippocampus. This frontal lobe hypothesis advocated the frontal lobes decline considerably faster than other brain areas. However, there is evidence for other brain regions changing substantially and evidence for other brain regions being implemented in executive function.
A second hypothesis for the decline of cognition in typical ageing is the disconnection hypothesis
A second hypothesis for the decline of cognition in typical ageing is the disconnection hypothesis which posits white matter damage disrupts communications between brain regions which leads to decline in complex cognition such as executive function.
Evidence for the disconnection hypothesis comes from Charlton et al (2010)
Evidence for the disconnection hypothesis comes from Charlton et al (2010) who found working memory declined over a 2-year period in 106 healthy middle aged and old aged adults but executive functions nor processing speed were significantly affected. This supports the disconnection hypothesis that white matter damage due to axonal loss causes age-related cognitive decline. Working memory may be particularly dependent on complex networks, dependent on white matter connections. Grey matter and white matter are connected and influence each other, a major risk factor influencing cognitive decline in ageing is hypertension as this increases the risk of developing white matter hypertensities (WMH) and vascular damage, which may lead to increased cardiovascular risk factors.
Ageing and pathological ageing can be seen as a continuum- cardiovascular risk factors may lead to cardiovascular disease which include coronary heart disease and stroke. (Yang et al, 2002).
Ageing and pathological ageing can be seen as a continuum- cardiovascular risk factors may lead to cardiovascular disease which include coronary heart disease and stroke. 87% of all strokes are ischaemic resulting from a restriction in blood supply causing a shortage of oxygen and glucose. The first stroke often goes unnoticed; it is a subcortical white matter stroke known as a transient ischaemic attack (TIA). TIA’s are the most common cause of vascular dementia. This small vessel disease leads to impaired function in attention, information-processing speed and executive functions. This lack of oxygen and glucose can lead to vascular dementia which is the second most common dementia and has a gradual onset and progression of symptoms in pathological ageing. It is characterised by a reduced blood flow in deep grey matter regions (Yang et al, 2002).
Ageing, primary deficits are in executive function. 10-15% McGuinness et al (2010)
Ageing, primary deficits are in executive function, but McGuinness et al (2010) found vascular dementia patients do not differ from Alzheimer’s disease on a number of different executive function tasks, showing vascular dementia is a risk factor to developing Alzheimer’s disease, the conversion from mild cognitive impairment to Alzheimer’s disease being approximately 10-15%. Vascular dementia is diagnosed when an individual has had no symptoms, followed by mild cognitive impairment (MCI), then Alzheimer’s disease and is due to a depletion of grey matter.
In terms of differences in cognitive decline between ageing and pathological ageing, Jack et al (1998)
In terms of differences in cognitive decline between ageing and pathological ageing, Jack et al (1998) found atrophy of hippocampal formation is 2.5 times greater in Alzheimer’s disease patients than in controls, with later changes in grey matter and white matter depletion being significantly greater in pathological ageing. There is also noted episodic memory impairment and additional early decline in semantic memory in the pathological ageing disease Alzheimer’s which later effects both white and grey matter as they are closely connected. This atrophy of the hippocampus may be due to plaques and tangles which are especially found in the hippocampus. However, these tangles are also found in typical ageing.
Conclusion
To conclude, typical ageing and pathological ageing are seen to lie on a continuum starting from cardiovascular risk factors, to small vessel disease, transient ischaemic attacks and strokes and potentially leading to vascular disease and Alzheimer’s disease.
