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Introduction
Ageing is an inevitable part of life that brings about significant changes in our bodies, including the brain. The ageing brain undergoes a process called senescence, which refers to the accumulation of harmful effects that make us more susceptible to disease and death. Although ageing increases the risk of neurodegenerative diseases, such as Alzheimer’s and Parkinson’s, not all age-related brain changes lead to severe impairment. Let’s delve deeper into how the brain ages and what happens to our cognitive abilities.
1 The Science of Ageing
Biologically, ageing is often measured not by the passage of time but by the increasing vulnerability to disease and death. The Gompertz law of mortality, established in the early 1800s by mathematician Benjamin Gompertz, states that the risk of death doubles every eight years after adulthood. This pattern of increasing vulnerability has remained consistent for centuries.
While life expectancy has dramatically improved in the last 150 years, this is largely due to advancements in treating non-age-related diseases, particularly those affecting infants and children. In 1850, the average life expectancy was less than 40 years; today, it hovers around 80 years. However, this increase in longevity does not imply that we age more slowly. The underlying ageing process remains the same, with cognitive decline becoming more prominent with advancing age.
2 Changes in Cognitive Abilities
Research led by Dr. Denise Park at the University of Texas at Dallas provides insights into how ageing affects different cognitive processes. In a study involving nearly 350 participants aged 20 to 92, Dr. Park’s team assessed various cognitive functions and identified three areas particularly affected by age:
i Processing Speed:
The ability to process information quickly declines progressively starting in our 20s, with each subsequent decade bringing a slight decrease in speed.
ii Executive Function:
This encompasses the brain’s ability to manage and oversee basic cognitive processes. A crucial part of executive function is working memory, which allows us to store and retrieve information temporarily. Age-related decline in working memory parallels the decline in processing speed.
iii Episodic Memory:
This type of memory involves recalling specific episodes from one’s life, such as personal experiences or events. Like processing speed and working memory, episodic memory also gradually declines with age.
3 Improving Cognitive Functions
Despite the declines in certain cognitive abilities, not all brain functions deteriorate with age. Some areas remain stable or even improve:
i Semantic Memory:
Unlike episodic memory, semantic memory, which relates to factual knowledge, remains relatively intact or can even improve with age. Older adults tend to perform better in vocabulary tasks than younger adults, likely due to accumulated knowledge over the years.
ii Implicit Memory:
Implicit memory involves unconscious processes, such as priming, where exposure to information influences the processing of related information later. This type of memory remains largely unaffected by ageing.
iii Procedural Memory:
This memory type involves skills and habits, such as riding a bike or tying a shoe, which tend to remain robust despite age-related changes.
4 Fluid vs. Crystallized Intelligence
Dr. Raymond Cattell proposed a distinction between fluid and crystallized intelligence in the 1940s:
Fluid Intelligence: Involves problem-solving and creative thinking that do not rely on acquired knowledge. Brain teasers and puzzles test fluid intelligence, which tends to decline with age.
Crystallized Intelligence: Depends on knowledge and experience accumulated over a lifetime. Older adults generally perform better on tasks that involve crystallized intelligence, such as vocabulary tests.
Dr. Park’s research aligns with Cattell’s theory, showing that older adults struggle more with fluid intelligence tasks but excel in tasks requiring crystallized intelligence.
5 Understanding the Decline and Its Onset
Processing speed plays a crucial role in age-related cognitive decline. As processing speed decreases, it impacts working memory and episodic memory. The onset and rate of this decline vary among individuals, and some cognitive impairment is not inevitable. Maintaining cognitive health can significantly influence the trajectory of cognitive decline.
Conclusion
The ageing brain is a fascinating subject, blending biology, psychology, and neuroscience. While ageing inevitably brings cognitive decline, understanding the mechanisms behind it provides insights into how to mitigate its impact. By recognizing which cognitive functions are most affected and which remain resilient, we can better appreciate the complexities of the ageing mind and potentially develop strategies to enhance brain health as we age.