Does Frailty Weaken Defenses Against Dementia?

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Becoming frail with age appears to make you more vulnerable to Alzheimer’s disease (AD), according to a 2019 study in Lancet Neurology.

Scientists have long been puzzled as to why the brains of some deceased people who had AD show only modest evidence of tangles and plaques, while the brains of other people who didn’t have the disease can be full of these protein formations. Could some unknown factor make people more or less susceptible to AD-related brain changes?

To investigate this question, Canadian researchers studied the medical records and brains of 456 men and women who had participated in an ongoing study of aging and had died. About half of the participants had been diagnosed as likely having AD. As part of the study, each participant’s frailty was rated based on 41 factors, such as whether they had debilitating conditions like congestive heart failure or struggled with fatigue. The study found that the least-frail people could have brains full of plaques and tangles, yet were never diagnosed with AD, while the most frail were also most likely to have these brain changes and have been diagnosed.

AD is a complex disease, but becoming frail may lower the threshold for associated brain changes to produce symptoms.