Frailty can make older adults more susceptible to Alzheimer's dementia, finds a study that suggests that frailty should be considered in clinical care and management of the age-related disease.

The study, published in the journal Lancet, showed that older adults with higher levels of frailty were more likely to have both Alzheimer's disease-related brain changes and symptoms of dementia. On the other hand, elderly 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," said lead author Kenneth Rockwood Professor at the Dalhousie University in Canada. 

"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," Rockwood added.

The findings support the idea that late-life dementia (and particularly Alzheimer's) is a complex phenomenon rather than a single disease entity marked by genetic risk or single protein abnormalities in the brain. "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," Rockwood said. 

In this study, the team used modelling to assess relationships between frailty, Alzheimer's-related brain changes, and Alzheimer's dementia among 456 participants. The analysis revealed that frailty and Alzheimer's disease-related brain changes independently contribute to dementia status, after adjusting for age, sex, and education.

Further, 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.