‘What’s this? A potato?’ asked my friend’s grandfather during lunch. As always, he used his charming grin and characteristically loud voice. Even though the entire conversation was in Argentine Spanish – which I had learned only a short while before – I understood the oddity of the situation at once. Instead of a potato, the grandfather held a kiwifruit in his hands.
After only a short time of living with this family I noticed that the grandfather no longer had the mental abilities he once must have possessed in order to lead a successful business and raise an adorable family. He was undiagnosed but his behaviour reminded me of Mild Cognitive Impairment, which can progress to a more severe general cognitive impairment – Alzheimer’s Disease or more generally dementia – which usually cannot be cured. ‘What can be done?’ I was asked by my friend’s grandmother afraid of slowly losing the husband she had shared most of her life with. In broken Spanish I tried to explain to her what I would do: build up a cognitive reserve. This concept – related to the beneficial effects of, for example, high education or mentally demanding spare time activities – is perhaps the most promising strategy for delaying dementia.
A large scale analysis illustrates what a cognitive reserve can achieve. First of all, it can delay dementia. An Australian research team (Valenzuela & Sachdev, 2006) collected studies which recruited old people when they were still perfectly healthy and then tested them again after a few years to find out by how much their cognitive abilities had declined. The trend across more than 47,000 people was for higher education and more demanding leisure activities to slow down the creeping loss of mental abilities leading to dementia.
A German nun without experimental confounds.
The savvy reader may already notice a problem with this theory: high education is associated with a generally healthier lifestyle. Rather than cognitive reserve, we should perhaps simply be talking about healthy vs. non-healthy life styles. A Bavarian study ruled this problem out (Bickel & Kurz, 2009). They gained access to the education and dementia records of older female members of a religious order who lived as similarly as one can imagine. The 442 participants had shared a roof for more than five decades, shared meals together, had the same access to medical care. None smoked. None had any personal items. And still, 39% of sisters with low education suffered from dementia, compared to only 14% in the remaining group. Clearly, whether life style has an effect or not, the benefits of a cognitive reserve cannot be reduced to it. It delays dementia all by itself.
This beneficial effect of a cognitive reserve led me to give my advice. However, this strategy cannot stave off dementia forever or even slow it down once it kicks in. Nikolaos Scarmeas and colleagues from Columbia University (2006) found that more highly educated New Yorkers above 65 lose their memory faster around the time of an Alzheimer’s disease diagnosis compared to less educated city dwellers. Apparently, the benefits of a high education are absent around the time of diagnosis.
This raises the obvious question whether my advice was perhaps too late. Once on the road to Alzheimer’s there may be no turning back and efforts to delay the inevitable could make things worse. Given what we know about how the cognitive reserve actually works, I do not believe that this is true. First of all, a cognitive reserve is no cure against dementia but merely a way to delay it. The theory goes that brain pathology progresses whether you have a cognitive reserve or not. What a high education level and demanding leisure activities actually do is to avoid the usual outcome of brain pathology – e.g., easily noticeable memory problems of the kind I have described above. This is supported by studies which compared the brains of people with equal mental function in high age. Those with higher education have more amyloid deposits – a peptide associated with Alzheimer’s disease – as if they were able to deal with their reduced brain function in a better way (Kemppainen et al., 2008; Rentz et al., 2010). At some point though, the progressively worse brain function catches up with you and the resulting cognitive decline is faster.
Charles Hall and colleagues (2007; 2009) tested this overall model in the real world. His analyses of memory test scores of over 100 Bronx residents over the years shows the predicted trend. At first, a high cognitive reserve – whether education or leisure activities – delays the point in time when mental abilities suddenly decline rapidly. Each year in education delays this moment by two and a half months. Each day of mentally stimulating leisure activities delays it by two months. Once this moment is reached, though, the decline is faster with a higher cognitive reserve – as if the aforementioned brain pathology catches up. A cognitive reserve helps you to delay dementia but not to escape it.
The higher the education the shallower the decline before a break point, the later that break point, and the steeper the decline thereafter.
My friend’s grandfather had long been out of education. But the second source of a cognitive reserve – mentally demanding leisure activities – was not beyond him. What sort of activities work? A French research team led by Tasnime Akbaraly (2009) took a better look. They found that only a certain kind of leisure activity will delay dementia onset. Watching television and other passive behaviours won’t do. Neither do physical activities like going for a walk. Nor social ones like have friends or family over. The crucial set of activities are the mentally demanding ones: doing crosswords, playing cards, attending organisations, going to the cinema/theatre, practicing an artistic activity etc.
It is a mystery to me why this knowledge is not more widely spread. Dementia is one of the central challenges facing an ageing population as well as many old couples individually. Research shows that one does not need to be a passive spectator of mental decline. If a cognitive reserve has been built up, one can enjoy more years without showing signs of an incurable disease. That’s what I tried to say in broken Spanish to my friend’s grandmother: make him use his mind.
Akbaraly, T., Portet, F., Fustinoni, S., Dartigues, J., Artero, S., Rouaud, O., Touchon, J., Ritchie, K., & Berr, C. (2009). Leisure activities and the risk of dementia in the elderly: Results from the Three-City Study Neurology, 73 (11), 854-861 DOI: 10.1212/WNL.0b013e3181b7849b
Bickel H, & Kurz A (2009). Education, occupation, and dementia: the Bavarian school sisters study. Dementia and geriatric cognitive disorders, 27 (6), 548-56 PMID: 19590201
Hall CB, Derby C, LeValley A, Katz MJ, Verghese J, & Lipton RB (2007). Education delays accelerated decline on a memory test in persons who develop dementia. Neurology, 69 (17), 1657-64 PMID: 17954781
Hall CB, Lipton RB, Sliwinski M, Katz MJ, Derby CA, & Verghese J (2009). Cognitive activities delay onset of memory decline in persons who develop dementia. Neurology, 73 (5), 356-61 PMID: 19652139
Kemppainen NM, Aalto S, Karrasch M, Någren K, Savisto N, Oikonen V, Viitanen M, Parkkola R, & Rinne JO (2008). Cognitive reserve hypothesis: Pittsburgh Compound B and fluorodeoxyglucose positron emission tomography in relation to education in mild Alzheimer’s disease. Annals of neurology, 63 (1), 112-8 PMID: 18023012
Rentz DM, Locascio JJ, Becker JA, Moran EK, Eng E, Buckner RL, Sperling RA, & Johnson KA (2010). Cognition, reserve, and amyloid deposition in normal aging. Annals of neurology, 67 (3), 353-64 PMID: 20373347
Scarmeas, N., Albert, S.M., Manly, J.J., & Stern, Y. (2005). Education and rates of cognitive decline in incident Alzheimer’s disease Journal of Neurology, Neurosurgery & Psychiatry, 77 (3), 308-316 DOI: 10.1136/jnnp.2005.072306
Valenzuela MJ, & Sachdev P (2006). Brain reserve and cognitive decline: a non-parametric systematic review. Psychological medicine, 36 (8), 1065-73 PMID: 16650343
1) By André Karwath aka Aka (Own work) [CC-BY-SA-2.5 (http://creativecommons.org/licenses/by-sa/2.5)%5D, via Wikimedia Commons
2) By Doris Ulmann, 1882–1934. [Public domain], via Wikimedia Commons
3) Hall et al., 2007, p. 1661
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