Ageing and the Brain

Original Editor - Created as part of the AGILE Project

Top Contributors - Alex Benham, Simisola Ajeyalemi, Kim Jackson, Lucinda hampton, Rubi, Rishika Babburu, Claire Knott, Tolulope Adeniji, Sai Kripa and Dinu Dixon  

One Page Owner - Urvisha Lunagariya as part of the One Page Project

Introduction

Brain function varies normally as people pass from childhood through adulthood to old age.

• During childhood, the ability to think and reason steadily increases, enabling a child to learn increasingly complex skills.
• During most of adulthood, brain function is relatively stable.
• After a certain age, which varies from person to person, brain function declines.

Common Age Changes

Some areas of the brain decrease in size by up to 1% per year in some people but without any loss of function.

Age-related changes in brain structure do not always result in loss of brain function.

A decrease in brain function with aging may be the result of numerous factors that include changes in brain chemicals (neurotransmitters),changes in nerve cells themselves, toxic substances that accumulate in the brain over time, and inherited changes.

Different aspects of brain function may be affected at different times:

• Short-term memory and the ability to learn new material tend to be affected relatively early.
• Verbal abilities, including vocabulary and word usage, may begin to decline later.
• Intellectual performance—the ability to process information (regardless of speed)—is usually maintained if no underlying neurologic or vascular disorders are present.

Morphological changes to the brain with ageing

• The volume of the brain is one of the more prominent changes due to neuronal loss, with an approximate reduction of 5% of brain weight, per decade, after the age of 40 Neuronal loss makes structures more pronounced such as the sulci of the cortex becoming deeper and the ventricles also becoming more pronounced
• The brain appears visibly different. Deposition of Brown (Lipofuscin) or black (Neuromelanin) pigments in the brain results in small discoloured areas due to normal ageing, although these are noted more in age-related brain pathologies such as Alzheimer's .

Physiological changes to the brain with ageing

• Cerebral blood flow has been shown to decrease by 27% decline over 70 years of age through direct changes in the cardiovascular system and may be exacerbated through blood vessel pathology .
• The effectiveness of the blood-brain barrier is found to be reduced with age and this leads to the increased opportunity for the pathogens and toxic materials crossing into the brain and the neural structures. Recent work has shown that this is often weakened in the hippocampus first which leads to damage to the area and can result in a cognitive decline to the function of the brain region.
• Ageing is also associated with declining production of some neurotransmitters, including noradrenaline, glutamate, dopamine and serotonin. Dopamine modulates motor-function and the acquisition of new skills and also one of the brain’s reward chemicals. The number of dopamine-producing neurons decreases as part of the normal ageing process, and this can adversely affect the ability to learn from past experiences .

Age Affects on Brain Function

The effects of ageing on brain function may be difficult to separate from the effects of various disorders that are common among older people. These disorders include depression, stroke, an underactive thyroid gland (hypothyroidism), and degenerative brain disorders such as Alzheimer disease.

• Short-term memory and the ability to learn new material tend to be affected relatively early.
• Verbal abilities, including vocabulary and word usage, may begin to decline later. There is a higher report of difficulties with recalling words in the older person, particularly after the age of 70.
• Reaction time and performance of tasks: Neuronal loss and the reduction in impulse velocity lead to a slowing of reaction times, and this can lead to problems with righting reactions, leading to eg falls
• Intellectual performance—the ability to process information (regardless of speed)—is usually maintained if no underlying neurologic or vascular disorders are present.
• Reaction time and performance of tasks may become slower because the brain processes nerve impulses more slowly.
• As people age, the number of nerve cells in the brain may decrease, although the number lost varies greatly from person to person, depending on the person’s health. In addition, some types of memory are more vulnerable to loss, such as memory that holds information temporarily.
• Sensorimotor performance is slower to achieve accuracy plus impaired sensory awareness to pain, touch, heat, cold and joint position sense. Impaired mechanism controlling posture, antigravity support, balance and moving equipoise (with nerve conduction velocity reduced 10% by the age of 75). Can be a major predisposition to falls and injury.

The Brains Resilience

The brain has certain characteristics that help compensate for these losses.

• Redundancy: The brain has more cells than it needs to function normally. Redundancy may help compensate for the loss of nerve cells that occurs with aging and disease.
• Formation of new connections: The brain actively compensates for the age-related decrease in nerve cells by making new connections between the remaining nerve cells.
• Production of new nerve cells: Some areas of the brain may produce new nerve cells, especially after a brain injury or a stroke. These areas include the hippocampus (which is involved in the formation and retrieval of memories) and the basal ganglia (which coordinate and smooth out movements).

People who have had a brain injury or stroke can sometimes learn new skills, as occurs during physiotherapy therapy.

People can influence how quickly brain function declines. eg. physical exercise seems to slow the loss of nerve cells in areas of the brain involved in memory. Such exercise also helps keep the remaining nerve cells functioning. On the other hand, consuming two or more drinks of alcohol a day can speed the decline in brain function.