Abstract
Background and purpose: The aim was to determine whether frailty is associated with the relationship between neuropsychological markers and global cognition in older adults.
Methods: Cross-sectional analyzes were conducted of baseline data from three large cohort studies: National Alzheimer’s Coordinating Center (NACC), Rush Memory and Aging Project (MAP) and Alzheimer’s Disease Neuroimaging Initiative (ADNI). Studies recruited North American participants along the spectrum of cognitive functioning (44% no cognitive impairment at baseline). A frailty index was computed in each dataset. Frailty indices, neuropsychological tests (including measures of processing speed, episodic, semantic and working memory) and Mini-Mental State Examination (MMSE) scores were the variables of interest, with age, sex, education and apolipoprotein E ε4 evaluated as confounders.
Results: Across all studies, 23,819 participants aged 55-104 (57% female) were included in analyzes. Frailty index scores were significantly and inversely associated with MMSE scores and significantly moderated relationships between neuropsychological test scores and MMSE scores. In participants with higher frailty index scores, lower neuropsychological test scores were more strongly associated with lower MMSE scores (standardized interaction coefficients ranged from -0.19 to -1.17 in NACC, -0.03 to -2.27 in MAP and -0.04 to -0.38 in ADNI, depending on the neuropsychological test). These associations were consistent across the different databases and were mostly independent of the composition of frailty indices (i.e., after excluding possible symptoms of dementia).
Conclusions: Amongst older Americans, frailty is associated with the cognitive expression of neuropsychological deficits. Implementation of frailty assessment in routine neurological and neuropsychological practice should be considered to optimize care outcomes for older adults.
Keywords: ageing; aging; cognition; dementia; frailty; neuropsychological tests; neuropsychology.
Plain language summary
This study looked at frailty – a measure of overall health status and vulnerability to harmful health outcomes – and cognitive function. Specifically, how frailty affects the relationship between cognitive function and neuropsychological markers in older adults. In other words, are neuropsychological markers such as a measure of processing speed affected by frailty? The researchers looked at data from three large studies that recruited participants with varying levels of cognitive function, including those without cognitive impairment. The analysis included 23,819 participants aged 55-104 years, with 57% being women. The researchers calculated a number that represents frailty (frailty index), a number that represents cognition (Mini-Mental State Examination), and numbers that represented performance on neuropsychological tests for each dataset. Then they analyzed the relationships between them.
The study found that with higher frailty index scores, Mini-Mental State Examination scores tended to be worse. Additionally, the researchers found that the relationship between neuropsychological test scores and Mini-Mental State Examination scores was significantly moderated by frailty. This means that participants with higher frailty index scores had a stronger association between lower neuropsychological test scores and lower Mini-Mental State Examination scores. These results were consistent across the different datasets. The study concludes that frailty affects the cognitive functioning of older people, and that assessing frailty should be a regular part of routine neurological practice to help make sure they get the best care possible.