Cognitive ageing and cognitive decline
Various biological, chemical and mechanical features characterize brain ageing. (Blinkouskaya & Weickenmeier, 2021). How and why we age and what we can possibly do to prevent that has been a fascination for humans throughout history. In fact, the first empirical study of the age-achievement relation has already been published in 1842 by Quetelet (Whitbourne, 2016).
At uni, we had only one month of looking into cognitive ageing and cognitive decline. Below you will find a brief summary illustrating the developmental process that the human brain goes through in old age, highlighting three aspects of cognitive decline; one preventive measure per aspect and two nutritional strategies to prevent cognitive decline.
The developmental process of the human brain through old age
Physiological changes associated with brain ageing include:
- Cerebrospinal fluid volume increase (Grant et al., 1987)
- Amyloid-beta plaques in the frontal lobe, hippocampus, and entorhinal cortex of healthy elderly (Blinkouskaya & Weickenmeier, 2021)
- Spatially heterogeneous age-related cortical thinning (Blinkouskaya & Weickenmeier, 2021)
- Hippocampal shrinking and ventricular enlargement (Blinkouskaya & Weickenmeier, 2021)
- Loss of cerebral white matter (Kochunov, et al., 2009)
- Reduced vascular supply (Jain & Rajkumar, 2006)
- Increased neuroinflammation (Benedetto & Müller, 2019)
- Changes in Brain-Blood Barrier (Anyanwu, 2007)
- Increase of grey matter volumes (Ramanoël, et al. 2018)
- Decrease in neurotransmitter (Acetylcholine, serotonin, and dopamine) level (Anyanwu, 2007)
Behaviourally, brain ageing is associated with:
- Metabolic slowing and decreased cellular regeneration. Which in turn leads to cognitive decline (Blinkouskaya & Weickenmeier, 2021)
- Change in processing speed (Kuznetsova, et al., 2015, para. 1)
- Changes in executive functioning (Huizinga, 2006)
Last in first out theory:
“The frontal lobes, home to key components of the neural circuitry underlying “executive functions” such as planning, working memory, and impulse control, are among the last areas of the brain to mature; they may not be fully developed until halfway through the third decade of life” (Johnson et al., 2009, p. 2).
“It has been proposed that the last parts of the brain to mature are the first to degenerate as we age. By analyzing structural MRI data from 484 healthy participants aged from 8 to 85 years, Douaud et al. now provide direct evidence for this assertion. They reveal a network of brain regions that develop late in adolescence and degenerate first in old age” (Douaud et al., 2014, para.1).
3 aspects of cognitive decline
1. Information processing speed
“Cognitive decline, especially the slowing of information processing speed, is associated with normal ageing. This decline may be due to brain cortico-cortical disconnection caused by age-related white matter deterioration” (Kuznetsova, et al., 2015, para. 1).
2. Attention
Attention is the selective process of concentrating on a specific aspect of information while disregarding the noise from other information. As we age, the executive processing resources slow down (Ayasse et al., 2017). For example, these attentional factors can impair listening effectiveness in older age because it is harder to filter out the noise (Tun et al., 2002).
A particular study “shows a case in which age-related reductions in attentional control over information that was not initially relevant can lead to superior performance for older adults” (Kim et al., 2007, para. 1).
3. Memory:
Another effect of slower processing speed is working memory decline with age (Borella, 2011). Working memory difficulties make it more difficult to hold information in mind and the reduction of plasticity makes it harder to store new memory (Singer et al., 2003).
A study by Alana T. Wong and Daniel L. Schacter (2008) demonstrates that “the age-related reduction of episodic specificity evident for past events extends to future events, a finding consistent with data from patients suggesting that deficits in memory can be associated with difficulties in imagining future experiences” (p. 39).
One possible preventive measure per aspect and its efficacy.
Some older adults maintain youth-like performance well into old age while others experience a sharp decline. Lifestyle measures, including nutrition and physical exercise, are established strategies for lowering cognitive impairment, building neural resources, and maintaining overall brain health (Wolbers, 2021; Demarin, et al., 2011).
Two nutritional strategies to prevent cognitive decline
Some people have shown well-preserved cognitive performance into old age, and factors such as brain reserve, cognitive reserve, brain maintenance, and compensation protect us from cognitive decline (Stern, et al. 2019). The optimization of nutrition may represent one of the first and theoretically most straightforward interventions employed to preserve health. The importance of micronutrients, trace elements, and vitamins are evident, and deficiencies in one or more of these nutrients impair cognitive function (Müller & Pawelec, 2014).
1. Avoidance of sugar
“One of the major changes that occur during ageing is the dysregulation of the immune response, leading to a chronic systemic inflammatory state” (Chung, et al., 2019, p. 3)
A recent longitudinal study of Japanese semi-supercentenarians revealed that inflammation, not telomere length, predicts successful ageing at a highly advanced age (Arak, 2015).
Recent evidence has shown that chronic inflammation is an underlying cause of age-related neurodegenerative diseases, and findings suggest that high-sugar diets can lead to cognitive impairment (Moreira, 2013).
“For example, several pro-inflammatory cytokines have been implicated in dementia and cognitive decline” (Chung, et al., 2019, p. 13).
“Hamsters fed with 60% fructose presented a decrease in neuronal insulin signalling in the cerebral cortex and hippocampus, and a subsequent impairment of synaptic function” (Moreira, 2013, p. 7).
2. Supplementing with vitamin C
Deficiencies in vitamin C levels are related to cognitive impairment (Harrison et al., 2009).
Vitamin C has been found to modulate inflammation, a hallmark of human ageing positively. It epigenetically regulates genome integrity and stability, indicating a pivotal role of vitamin C in healthy ageing (Monacelli et al., 2017).
“Mice with the high dosage of vitamin C showed a reduced number of plaques in the frontal cortex”, “decreased amyloid plaques were observed in the hippocampus”, and “these findings suggest that the higher dose of vitamin C intake could reduce amyloid plaque deposition in the brain” (Kook, et al., 2014, p. 2).
Conclusions cognitive ageing and decline
- The ageing brain goes through significant functional and structural changes.
- Cognitive decline is a decline in information processing speed, attention, and memory, among others.
- Mechanisms protecting us from cognitive decline include the build-up of the reserve, brain maintenance, compensation and strategic adaptations.
- Positive lifestyle adjustments, including education, nutrition and physical activity, can make the brain more resilient and preserve cognitive functioning.
- Avoiding sugars and Vitamin C supplementation are two nutritional strategies to support healthy ageing.
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