DNC News

Cognitive Reserve:

January 10, 2006

Subject: How fast our minds fade with age depends how much brain power we start with or how much we were able to build up during our prime.

 

Our mental abilities peak around age 25. We won't discuss how long ago that was for some of us. From then on the speed at which we process information, store new memories, reason or process spatial data slowly but surely slows. The smarter you are to begin with the more slowly this becomes a problem. If you start out with more in reserve, it takes longer to run out. This might sound obvious, but it's only recently that this hypothesis of ‘cognitive reserve' has been accepted by researchers.

 

The first evidence was Yaakov Stern's work. Stern measured the 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 was. This suggested some kind of ‘padding' which shielded more educated patients from the looking as bad as would be expected from the physical condition of their brains. [i] Stern's more recent work says that beyond education, how mentally engaged a person is makes a difference. [ii] The studies have piled up supporting the cognitive reserve hypothesis. Better-educated people suffer less cognitive impairment for a given level of brain damage. Highly educated people are also less likely to experience a pronounced dip in IQ after a head injury.

 

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. What is happening is that by the time symptoms appear, these people are at a relatively late stage of the disease. If you measure the physical progress of the disease, they are already far gone 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.

 

Building cognitive reserve is a lifetime enterprise, and the earlier we start the better off we are. Social class, occupation and education at age 26 have been shown to shape cognitive ability at age 53. The more education, the more cognitive reserve a person has later in life. What you start with still matters. The best predictor of cognitive ability in middle age is your IQ score at age 8. People who work at complex occupations are also somewhat protected against the risk of dementia and Alzheimer's disease.

 

Although scientists are using big terms here, it's simply a matter of use it or lose it. Using your brain, continuing education, engaging work, stimulating thought, all appear to help maintain function. I'm waiting for the definitive study on the effect of TV, but I think we can guess. One does wonder about video games though.

 

Perhaps I shouldn't have let my subscription to the New York Times lapse.

 

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:

1. Stay Alert: Mental activity builds up reserves of brain cells and connections which protect against age-related decline.

2. 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.

3. 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?

4. Eat Right: A diet high in mono and polyunsturated acids (fish and olive oils), vitamin E, polyphenols and antioxidants may slow decline.

5. Stay Sober: Smoking, alcohol and street drugs all fry brain cells.

 

 

 

[i]

Ann Neurol. 1992 Sep;32(3):371-5.

Related Articles, Links


Inverse relationship between education and parietotemporal perfusion deficit in Alzheimer's disease.

Stern Y , Alexander GE , Prohovnik I , Mayeux R .

Department of Neurology, Columbia University , College of Physicians and Surgeons, New York , NY .

A higher prevalence of dementia in individuals with fewer years of education has suggested that education may protect against Alzheimer's disease (AD). We tested whether individuals with more years of education have a more advanced AD before it is clinically evident. As a measure of pathophysiological severity, we quantified regional cerebral blood flow (rCBF), by the 133Xenon inhalation technique; a specific pattern of flow reduction in the parietotemporal cortex corresponds to AD pathology. In 3 groups of patients with probable AD, matched for clinical measures of dementia severity but with varying levels of education, whole-cortex mean flows were comparable. However, the parietotemporal perfusion deficit was significantly greater in the group with the highest level of education, indicating that AD was more advanced in this group. We conclude that education or its covariates or both may provide a reserve that compensates for the neuropathological changes of AD and delays the onset of its clinical manifestations.

PMID: 1416806 [PubMed - indexed for MEDLINE]

 

[ii]

Arch Neurol. 2003 Mar;60(3):359-65.

Related Articles, Links

Click here to read 
Association of life activities with cerebral blood flow in Alzheimer disease: implications for the cognitive reserve hypothesis.

Scarmeas N , Zarahn E , Anderson KE , Habeck CG , Hilton J , Flynn J , Marder KS , Bell KL , Sackeim HA , Van Heertum RL , Moeller JR , Stern Y .

Cognitive Neuroscience Division of the Taub Institute for Research in Alzheimer's Disease and the Aging Brain, College of Physicians and Surgeons of Columbia University, New York, NY 10032, USA. ns257@columbia.edu

BACKGROUND: Regional cerebral blood flow (CBF), a good indirect index of cerebral pathologic changes in Alzheimer disease (AD), is more severely reduced in patients with higher educational attainment and IQ when controlling for clinical severity. This has been interpreted as suggesting that cognitive reserve allows these patients to cope better with the pathologic changes in AD. OBJECTIVE: To evaluate whether premorbid engagement in various activities may also provide cognitive reserve. DESIGN: We evaluated intellectual, social, and physical activities in 9 patients with early AD and 16 healthy elderly controls who underwent brain H(2)(15)O positron emission tomography. In voxelwise multiple regression analyses that controlled for age and clinical severity, we investigated the association between education, estimated premorbid IQ, and activities, and CBF. RESULTS: In accordance with previous findings, we replicated an inverse association between education and CBF and IQ and CBF in patients with AD. In addition, there was a negative correlation between previous reported activity score and CBF in patients with AD. When both education and IQ were added as covariates in the same model, a higher activity score was still associated with more prominent CBF deficits. No significant associations were detected in the controls. CONCLUSIONS: At any given level of clinical disease severity, there is a greater degree of brain pathologic involvement in patients with AD who have more engagement in activities, even when education and IQ are taken into account. This may suggest that interindividual differences in lifestyle may affect cognitive reserve by partially mediating the relationship between brain damage and the clinical manifestation of AD.

PMID: 12633147 [PubMed - indexed for MEDLINE]

 


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