Cognitive Reserve: Use it or Lose it

Most people envision their “golden years” filled with pursuits of post-retirement enjoyment and assume they will have a healthy body, mind, and spirit. Although aging is inevitable, some people appear to “age” much faster, leaving them unable to fully enjoy these pursuits, while others seem to be “forever young” and active. Which one will you be?

How fast our minds fade with age depends on how much brainpower we start with and how much more we build up during our prime. There is a concept regarding mental function called “cognitive reserve” which is the brain equivalent of bone density. The amount of bone density one starts out with helps determine risk of developing osteoporosis, because the process of aging guarantees some bone density loss. When bone density drops too low, osteoporosis is diagnosed. Similarly, cognitive reserve is a measure of how well the brain works at the peak of function, which neurologists estimate at age 25. For those who start with more brainpower, it takes longer to notice loss of cognitive function. It's only recently that researchers have accepted this hypothesis of “cognitive reserve.”  

Yaakov Stern PhD, Professor of Clinical Neuropsychology at the Sergievsky Center and the Taub Institute, demonstrated the first evidence of cognitive reserve. Stern measured the brain blood flow in Alzheimer patients.  Grouping patients by severity of outward symptoms, he found that the higher the level of education the more severe the actual brain damage.  He hypothesized there is some type of 'padding' which protects more educated patients from showing as many symptoms of dementia as would be expected from the physical condition of their brains.  Stern's more recent work notes that beyond education, how mentally engaged a person is effects mental function later in life even more than education alone.  

In 2012 Stern published a review of multiple cognitive studies. He observed that the epidemiologic evidence suggests that experiences at all stages, even in late life, can impart cognitive reserve. These findings support the possibility that it may be possible to intervene even later in life in order to impart reserve, slow age-related cognitive decline, and prolong healthy aging. The most successful remediation approach to date has been aerobic exercise. It was also demonstrated that complex gameplay was associated with improved performance on a wide range of cognitive tasks. (1)

The epidemiologic data clearly suggests that aspects of life experience can impart reserve against age or disease-related pathology. However, the exact "recipe" for helping to create this reserve is still unknown.

Studies have accumulated supporting Stern’s cognitive reserve hypothesis. Katzman et al., 1988, noted that bigger brains tolerate more loss before exhibiting impaired function because of a higher number of healthy synapses or neurons. When disease occurs it takes longer to “run out” of healthy nerve cells.

In 2002, Stern suggested when there is more efficient use of brain networks, disease symptoms take longer to appear. For example, a trained mathematician might be able to solve a mathematics problem many different ways, while a less-experienced individual might have only one possible solution strategy available. This built-in redundancy permits greater resilience in the face of brain damage.

A number of factors determine cognitive reserve: some can be controlled, while others cannot. The stimulation provided by everyday intellectual and social activities facilitate the maintenance of cognitive skills in a manner that is analogous to physical exercise for optimal heart health. Surprisingly, the best predictor of cognitive reserve in middle age is the IQ at age 8, while the level of education and working at engaging professions or participating in mentally challenging pursuits also help. Building cognitive reserve is a lifetime enterprise, and the earlier we start the better off we are.

Once people with high IQ, good education or occupational achievement are diagnosed with dementia, they tend to go downhill particularly fast. For example, well-educated people with Alzheimer's disease seem to die sooner after diagnosis than people without good education.

This makes sense. It's not that people with high education and with Alzheimer's disease deteriorate faster. By the time symptoms appear, these people are at a relatively late stage of the disease. If the physical progress of the disease is measured, it is already far progressed when diagnosed. As long as they have cognitive reserve in the bank, outward signs are not apparent. Yet the disease progresses regardless, and once that extra cushioning goes, the outward decline is dramatic.

Animal studies and some small-scale human trials suggest there may be some things we can do to both develop and preserve this cognitive reserve:
  • Stay Alert:  Mental activity builds up reserves of brain cells and connections which protect against age-related decline.
  • Keep Fit:  Exercise keeps the blood flowing to the brain and may trigger the birth of new brain cells.  Fitness strengthens the brain's executive function and preserves both white and grey matter.
  • Minimize Stress:  Anxiety prone people appear to have a faster rate of cognitive decline.  Of course if your brain was slipping away on you, wouldn't you be feeling some anxiety?
  • Eat Right: A diet high in mono and polyunsaturated fatty acids (fish and olive oils), vitamin E, polyphenols and antioxidants may slow decline. Foods rich in choline may be helpful: emphasize foods including whole grains, legumes, egg yolk, broccoli family vegetables and nuts. Supplemental phosphatidylserine, a nutrient found most concentrated in the brain that contributes to the basic structure and function of nerve cells, may be worth considering.

    Recent research also points to certain “purple foods” as being protective against brain damage. Three stand out: Pomegranate juice slows disease progression by half in rats bred to develop Alzheimer’s; Resveratrol, a chemical isolated from grape skins may actually dissolve the beta-amyloid plaques which cause Alzheimer’s; and Blueberries which continue to show up in the research as protective against damage to brain cells.
  • Stay Sober:  Smoking, alcohol and street drugs all kill brain cells.
Although scientists are using big terms to describe this phenomenon, it's simply a matter of use it or lose it. Using your brain, continuing education, engaging work, stimulating thought, and social activity, all appear to help maintain function and help ensure that you will be able to enjoy and remember your “golden years.”

Cognitive reserve in ageing and Alzheimer's disease. Yaakov Stern, PhD. Lancet Neurol. 2012 Nov; 11(11): 1006–1012. doi: 10.1016/S1474-4422(12)70191-6

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