Frailty makes older adults more susceptible to dementia and moderates the effects of dementia-related brain changes on dementia symptoms, new research suggests.
That means individuals with few Alzheimer’s disease-related brain changes may be at risk of dementia if they are frail, but also that there may be more potential treatment options to explore, the researchers say.
A team from Nova Scotia Health Authority and Dalhousie University in Canada studied 456 adults aged over 59. They found that those with higher levels of frailty were more likely to have both Alzheimer’s disease-related brain changes and symptoms of dementia, while others with substantial brain changes, but who were not frail, showed fewer clinical symptoms.
“By reducing an individual’s physiological reserve, frailty could trigger the clinical expression of dementia when it might remain asymptomatic in someone who is not frail,” says study leader Kenneth Rockwood.
“This indicates that a ‘frail brain’ might be more susceptible to neurological problems like dementia as it is less able to cope with the pathological burden.”
The findings are reported in a paper published in the journal The Lancet Neurology.
The authors caution that this was a single study based on a cross-sectional comparison of pathology data from a database that only includes adults living in Illinois in the US.
However, the findings support the idea that late-life dementia (particularly Alzheimer’s disease) is a complex phenomenon rather than a single disease marked by genetic risk or single protein abnormalities in the brain.
“This is an enormous step in the right direction for Alzheimer’s research,” Rockwood says, adding that “understanding how individual risk factors work together to give rise to late-life dementia is likely to offer a new way to develop targeted treatment options”.
Most people who develop Alzheimer’s dementia are older than 65 and have several other health problems. Frailty – which is linked to reduced physiological reserve and increased vulnerability to other ailments – is associated with age and higher rates of cognitive deficit and dementia, but little research has explored how these conditions might be related.
All the participants in the latest study were involved with the Rush Memory and Ageing Project (MAP) – a longitudinal clinical-pathological study of older adults living in Illinois which began in 1997.
The analysis revealed that frailty and Alzheimer’s disease-related brain changes independently contribute to dementia status, after adjusting for age, sex and education. It also found a significant association between frailty and Alzheimer’s disease-related brain changes after excluding activities of daily living from the frailty index and adjusting for other risk factors such as stroke, heart failure, high blood pressure, and diabetes.
“While frailty is likely to reduce the threshold for Alzheimer’s disease-related brain changes to cause cognitive decline, it probably also contributes to other mechanisms in the body that give rise to dementia, weakening the direct link between Alzheimer’s disease-related brain changes and dementia,” says Rockwood.
“While more research is needed, given that frailty is potentially reversible, it is possible that helping people to maintain function and independence in later life could reduce both dementia risk and the severity of debilitating symptoms common in this disease.”
Nick Carne is the editor of Cosmos Online and editorial manager for The Royal Institution of Australia.
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