Brain health: The importance of keeping mentally active for reducing the risk of Alzheimer’s disease

To mark Dementia Action Week 2021, this blog highlights the importance of keeping mentally active to help reduce the risk of Alzheimer’s disease.

(The full author list is: Jemma Pitt, Andrew Quinn, Sarah Clayton and Méadhbh Brosnan, from the Brain & Cognition lab.)

The famous story of Sister Mary¹, an older nun who aged with remarkable positivity and good health until her death aged 101, dates back to the early 1900’s. She was well known for scoring highly on cognitive assessments even though her brain exhibited signs of Alzheimer’s Disease. In other words, she had Alzheimer’s in her brain, but was not presenting with any symptoms of the disease. This intriguing case prompted studies into understanding individual differences in resilience to Alzheimer’s Disease, to find out why some people with damage to the brain exhibit signs of the disease, but others do not.

Cognitive reserve

A groundbreaking piece of research published in 1992 highlighted how an individual’s resilience to Alzheimer’s Disease differed according to how they had spent their time². This particular study showed that individuals with greater levels of education were less impacted by Alzheimer’s related brain damage and symptoms of the disease. However, it has since become clear that it is not just education that results in this resilience. We now know that a wide range of cognitively enriched environments including hobbies, occupational engagements, social and leisure activities are effective in building resilience against the symptoms of Alzheimer’s Disease³. This has become known as ‘cognitive reserve.’

One recent compelling study³ followed over 1600 older adults as they aged, and saw that individuals who had kept themselves more cognitively engaged were 40% less likely to show clinical symptoms of Alzheimer’s disease. Over 600 of these older adults kindly donated their brains to science. Their autopsies revealed that cognitive engagement reduced the symptoms of the disease, even for people with high levels of Alzheimer’s-related damage to the brain.

Future research

While the benefits of enriched cognitive environments are clear, how enrichment impacts the brain in such a profound and useful way is a topic which is both scientifically interesting and one which will help us to develop better treatments to improve resilience to cognitive decline. One current focus of our work is to understand precisely how enriched environments alter the structure and function of the brain to support resilience against Alzheimer’s Disease. Cognitively enriched environments (e.g., like learning to read, dance, or play guitar, spending time with your family, driving on an unfamiliar motorway) typically demand certain mental operations. These include staying alert, focused, concentrated, monitoring mistakes, and exposure to new situations⁴. These activities rely, to some extent, on a collection of connected brain areas known as the right hemisphere frontal-parietal networks⁴. Interestingly, studies have shown that older adults who engage in cognitively stimulating activities display differences in these regions, which suggests that cognitive ‘brain exercise’ may strengthen these important brain networks to facilitate resilience.

Another important avenue for Alzheimer’s research is to understand how the brain is communicating within and between these different brain structures. To do this, a brain scan known as ‘Magnetoencephalography (MEG)’ can be used to ‘listen’ to electrical activity in the brain whilst a volunteer completes simple tasks. Neurons in the brain use these electrical signals to communicate, so the MEG allows us to observe how different parts of the brain are co-ordinating information, and how this is impacted by Alzheimer’s Disease. This precise synchronisation is important to measure the very earliest changes in degeneration and is likely to be the period where treatments (such as cognitive enrichment) are most effective.

Whilst the scientists continue to unravel how best to measure Alzheimer’s Disease and how resilience can alter the structure and coordination of information throughout the brain, keep in mind that The Lancet Commission for dementia prevention (2020) estimates that 40% of Alzheimer’s cases are attributed to modifiable risk factors including staying mentally active and engaged. This means that continuing to explore and learn throughout a whole lifetime can reduce your risk of developing dementia in later life. Perhaps you have always dreamt of taking up the saxophone, learning to tango, or starting Italian? We say start now! Your brain will thank you later.... 

Additional Information

For other modifiable risk factors for dementia check out the following infographic: https://www.thelancet.com/infographics/dementia-risk) and read more about the ‘Think Brain Heart’ initiative here (https://www.thinkbrainhealth.org/about/recommendations/). Their slogan is ‘what’s good for the heart is good for the brain’.

If you are interested in hearing more about our dementia research studies at Oxford, please contact the team on brainhealthresearch@psych.ox.ac.uk.

Sources:

1. Sister Mary: https://pubmed.ncbi.nlm.nih.gov/9127971/
2. 1992 paper (Stern et al, Annals of Neurology): https://pubmed.ncbi.nlm.nih.gov/1416806/
3. 2019 paper (Xu et al, JAMA Neurology): https://pubmed.ncbi.nlm.nih.gov/31302677/. Differences in the resilient ageing brain.
4. Robertson (2013, Neurobiology of Aging) https://pubmed.ncbi.nlm.nih.gov/24378088/;
5. Mok et al (2019, Neuroimage) https://pubmed.ncbi.nlm.nih.gov/30905834/
6. Brosnan et al (2017, Cerebral Cortex) https://pubmed.ncbi.nlm.nih.gov/28444373/
7. Van Loenhoud et al (2017, Human Brain Mapping) https://pubmed.ncbi.nlm.nih.gov/28631336/
8. Shalev et al (2021, Cerebral Cortex Communications) https://pubmed.ncbi.nlm.nih.gov/33073236/