Cognitive activities such as human reaction time, attention, memory, reasoning, visuospatial abilities and language decline with normal aging. Neurological research has found that these changes could be related to a reduction in the volume of the brain’s gray and white matter with a decrease in the levels of the neurotransmitters. Although the changes are relatively minor without impairment of function some activities such as driving may be affected. A majority of the older adults above 65 years of age rarely develop dementia. Neurocognitive changes seen in normal aging include:
Intelligence can be divided into fluid and crystallized cognition. Fluid intelligence is a person’s inborn ability to learn new things, resolve developing problems and adapt to environmental changes. Human reaction time and psychomotor skills peak around the 30s and then decline over time. Crystallized intelligence includes knowledge acquired over time, which is familiar and practiced. This is acquired through life’s experiences and therefore, the elderly perform better with this type of cognitive skills compared to younger adults.
The speed of processing includes the speed of an individual’s motor responses as well as cognitive skills. These start to decline in the 30s and influence abilities like verbal fluency.
The decline in memory with aging is probably secondary to the decline in processing speed, inability to simultaneously process multiple sensory inputs and diminished ability to learn. The ability to acquire information declines with age but the ability to retain information which is already learned. There are two types of memories: declarative and non-declarative.
Declarative memory includes semantic memory (e.g. language, the meaning of words etc) and episodic memory (e.g. memory of past events etc). These decline at different times with episodic memory declining throughout life while semantic memory declines later in life.
Non-declarative memory does not decline during an individuals’ life. Examples of this time of memory are swimming, riding a bicycle and tying shoelaces.
Attention is the ability to focus and concentrate on specific tasks. Older adults have difficulty multi-tasking, participating in conversations in noisy environments and retaining information in memory and simultaneously manipulating it. This can result in practical problems e.g. difficulty driving, calculating tips in a restaurant etc.
The ability to assemble and construct (visual construction) e.g. a jigsaw puzzle, can decline with age but the ability to recognize familiar faces and objects (visuospatial) remains intact.
Normal aging is associated with a decline in verbal fluency and naming objects after the seventh decade although overall language skills do not decline with age.
Executive functioning is the ability to plan, solve problems and reason logically etc. Normal aging is associated with a decline in mental flexibility, response inhibition and motor components requiring speed after the age of 70. Mathematical reasoning, however, can decline to start around the fourth decade. Abilities, like appreciating similarities or describing proverb meanings, do not decline.
Pathological Cognitive Decline
Cognitive decline beyond normal age-related decline is known as mild cognitive impairment (MCI) and it is further classified as amnestic and non-amnestic.
Amnestic MCL is characterized by normal or minimally impaired ADLs, symptoms of memory impairment noticed by an observer, delayed recall test indicative of objective memory impairment and mild general cognitive decline. These patients are more likely to develop Alzheimer’s disease.
Non-amnestic MCI is further divided into single domain impairment and multiple domain impairments.
Progressive acquired cognitive skills and memory impairment associated with functional decline is called dementia syndrome. Although AD is reported to be the commonest type of dementia, postmortem studies indicate that the decline is due to a combination of vascular and tau-related AD. Lewy body dementia, frontotemporal dementia, dementia associated with metabolic syndromes, trauma, malnutrition and central nervous system infections constitute other causes of pathological cognitive decline.
Alzheimer´s Disease (AD)
Alzheimer’s disease (AD) is characterized by a gradual onset and progressive cognitive, functional and neuropsychiatric decline. The Early stage of AD is associated with an inability to manage personal finances while mood changes develop in the intermediate stage. The AD patient gradually becomes dependent on the caregiver for all ADLs.
Tests for assessing cognitive impairment
- History: It is important to obtain a detailed history from an observer/ relative/ caregiver about the cognitive impairment noted in the individual over a period of time. It is essential to inquire about medications, alcohol intake and co-morbidities which may all contribute to the decline.
- Physical and neurological examination: Besides a general examination and a detailed neurological examination, a Mini-Mental State examination and a Mini-Cognitive examination with three item recall and drawing a clock should be performed.
- Laboratory tests to exclude vitamin deficiencies, thyroid dysfunction and cardiovascular abnormalities are indicated in all cases of dementia. In addition, a complete blood count, comprehensive metabolic panel and a test for syphilis should also be ordered.
Delaying Cognitive Decline
Scientific reports indicate that cognitive decline can be prevented or delayed participating in a combination of activities to stimulate cognition such as language and higher educational training, increasing the complexity of work and leisure activities. The cognitive declines in vary between individuals. Factors like genetics, co-morbidities, and sensory deficits like hearing loss or visual impairment contribute to the decline. Improving cognitive reserve, participating in intellectual, social and physical activities in combination with retraining may be helpful.
Following is a list of activities associated with delaying or preventing cognitive decline in the elderly:
- Intellectual activities e.g. higher education, learning a new language, working in high complexity occupations, reading, learning to use the computer, playing board games or bridge
- Physical exercise to improve cardiac health, gardening, and dancing
- Social activities e.g. traveling, volunteering, activities with friends and family