New findings from dementia research: Why some people are resilient to memory loss

Kyoto (ptp011/16.09.2017/13:30) 90+, plaques in the brain yet still mentally fit: Experts at the World Congress for Neurology in Kyoto discussed why some people are more susceptible to develop memory loss symptoms and others are not. New studies show what keeps people cognitively healthy.

Why do some people get dementia in old age and others do not, even if they reach a highly advanced age? International experts are currently delving into the issue of forgetting at the XXIII World Congress for Neurology in Kyoto. Prof Claudia Kawas from the University of California, Irvine, has researched the cognitive condition of oldest-old in "The 90+ Study". The long-term study involved over 1,700 participants, making it the largest of its kind. "It is important to study the oldest-old. We can learn a lot from this fastest growing age group," Prof Kawas notes. According to life expectancy projections published by Danish and German experts, most babies born since 2000 in France, Germany, Italy, the UK, the USA, Canada, Japan, and other countries with long life expectancies will celebrate their 100th birthdays. "In view of the demographic developments, delay of cognitive decline is crucial," Prof Kawas says. "We have calculated that if interventions could delay the onset of Alzheimer's disease in those afflicted by two years, there would be - in the US alone - nearly 2 million fewer cases than projected by 2050."

It turns out that 40 percent of the 90+ Study participants had dementia diseases, with women being more heavily affected than men. "Interestingly enough, autopsies revealed that about half of the oldest-old without dementia have a high-degree of Alzheimer's neuropathology in their brains although they were mentally fit while alive," Prof Kawas explains. Conversely, half of the dementia patients did develop symptoms of cognitive loss without this kind of pathologies in the brain.

Healthy lifestyle helps to remain mentally fit

The reasons for this cognitive resilience - which in this study is defined as having Alzheimer pathologies while not showing dementia symptoms - may be attributable in part to lifestyle. The group of resilient study participants, for example, got more exercise, and watched less TV.

Education manifested itself particularly important as a protective factor in individuals who were shown in PET scans to have plaque in the brain typical of Alzheimer's: "People with a low level of education had a four times higher statistical risk of contracting dementia than those with a higher level of education. Among people without plaque, the educational difference was irrelevant," Prof Kawas notes.

Another interesting finding relates to multiple pathologies. "Multiple brain pathologies are at the root of dementias at all ages," Prof Kawas reports. "In the oldest-old, the presence of multiple pathologies is associated with increased likelihood of dementia. The number of pathologies also seems to be relevant for the severity of the cognitive decline. We will therefore need to target multiple pathologies to reduce the burden of dementia."

Keep body and brain working to hold dementia at bay

Major uncertainties continue to persist when it comes to the question of how dementias can be prevented or their progress retarded at all ages. This is the focus of "Preventing Cognitive Decline and Dementia", a study of the National Academies of Science, Engineering and Medicine, which is determining the current state of research on behalf of the National Institute on Aging (NIA). "No specific interventions for maintaining cognitive health were able to be identified. However, the overarching message we can derive from the findings so far is: Keep your body and brain working in order to protect cognition," Prof Kawas says.

Cognitive training includes, for example, problem-solving tasks or exercises that put demands on memory or the speed of mental processing. There is currently no evidence of the efficacy of commercial computer-based brain training exercises. They appear to have only short-term effects and just in connection with the same tasks that are practiced over and over, Prof. Kawas notes.

Physical activity - or the lack thereof - was identified as one of the risk factors open to influence that has the greatest effect on cognitive disorders and dementia. A study (AHRQ Systematic Review) shows that exercise can play a part in postponing or slowing down age-related cognitive decline. On including data from a prospective cohort study and findings from neurobiological processes, the study committee decided, however, that the conclusive evidence has not yet been furnished in this regard.

Getting high blood pressure under control appears to be important for cognitive health as well. That is especially true of mid-life between ages 35 and 65. Even if decisive evidence has not yet been furnished, there are increasing indications that keeping high blood pressure in check can prevent, postpone or retard dementia. "Interestingly, while blood pressure control is generally an important preventive factor, the picture is slightly different in the 90+ age group", Prof Kawas says. "In the oldest-olds, there are indications that higher blood pressure might even have a certain protective effect."

Research approaches with a sharper focus

"People should be suitably informed about what they can do to prevent cognitive decline from the standpoint of today's scientific knowledge. The results of the report do not form a suitable basis for deriving public health strategies to counter the wide-spread disease of dementia. We need further studies to be able to better assess the effect of potential measures," Prof. Kawas emphasized. The committee suggested taking research approaches that are more refined, that examine different segments of the population separately and for example, that consider the ethnic or socioeconomic background of people or the time at which anti-dementia interventions are taken. It also said that further treatments for the affected individuals had to be incorporated. These include new anti-dementia treatments, diabetes and depression therapies, lipid-reducing drugs, the administration of B12plus folic acid or interventions focusing on nutrition, sleep quality or social involvement.

Sources: The 90+ Study: www.90study.org; Leshner et al, Preventing Cognitive Decline and Dementia. A Way Forward, Washington (DC): National Academies Press (US); 2017 Jun. The National Academies Collection: Reports funded by National Institutes of Health.

https://www.ncbi.nlm.nih.gov/pubmed/28650595; Christensen et al. Aging populations, the challenges ahead. The Lancet, Volume 374, No. 9696, p1196-1208, 3 October 2009; Kawas et al. Multiple pathologies are common and related to dementia in the oldest-old. Neurology. 2015 Aug 11;85(6):535-42.

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