Background
Some of the most important tools used in the diagnosis of Alzheimer’s are various brain imaging techniques, including magnetic resonance imaging (MRI) and positron emission tomography (PET). These can be used to show abnormalities in the brain, including the shrinking of certain areas, which is a key feature of Alzheimer’s. It is thought that the severity of Alzheimer’s symptoms correlates with the degree of abnormalities seen in the brain. However, some people with Alzheimer’s show only mild symptoms even though they have many abnormalities in their brain scans. This discrepancy may be due to several factors, but one could be the level of ‘cognitive reserve’ – this is the brain’s ability to adapt to changes, and look for alternative ways to carry out its usual functions. In other words, the brain’s resilience and capacity to deal with damage. Cognitive reserve is linked to several lifestyle factors including education, occupation, and leisure activity.
Why is the study important?
This study aims to better understand why some people show less severe Alzheimer’s symptoms despite having high level of abnormalities in brain imaging scans, and whether this is linked to various lifestyle factors. This may provide evidence for the effectiveness of various lifestyle interventions in slowing down the progression of Alzheimer’s.
What did the authors do and how did they do it?
135 people with Alzheimer’s were recruited from memory clinics at Tokyo General Hospital and Tokyo Medical University Hospital. The authors measured the severity of Alzheimer’s symptoms using the mini mental state examination (MMSE), a commonly used test for Alzheimer’s symptoms. They also obtained two types of brain scan, and calculated the difference between these and the expected brain scan based on MMSE results. They sorted the participants into three categories; positive difference (high number of abnormalities in the brain scans, but lower levels of symptoms), no difference (similar levels of brain scan abnormalities and symptoms) and negative difference (lower levels of brain scan abnormalities and higher levels of symptoms).
They also obtained information about lifestyle including number of years in education, and longest held occupation. They assessed the type and amount of leisure activity over the last 12 months including physical activities such as walking, swimming, and sports, cognitive activities such as reading, writing, and playing games such as cards, and social activities such as volunteering, going to the cinema or a concert, and visiting museums.
What are the results?
The researchers found that age, gender, and time since diagnosis did not differ between the positive difference, no difference, and negative difference groups. However, education, and level of leisure activity was significantly higher in the positive difference group than in the other groups. The no difference and negative difference groups were similar in education and level of leisure activity. This suggests that a higher cognitive reserve (as measured by education, and levels of leisure activity) can be used to explain differences between severity of Alzheimer’s symptoms and abnormalities seen in brain imaging scans.
What do the findings mean going forward for people with the disease?
The findings of this study suggest that people with a high cognitive reserve are more likely to show milder symptoms of Alzheimer’s even when brain scans show more severe abnormalities. Whilst the precise mechanisms leading to increased cognitive reserve are not well understood, it is thought that a wide variety of leisure activities contribute, suggesting that lifestyle interventions including physical, cognitive, and social activities, may help to slow the progression of Alzheimer’s symptoms.