Search

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. [ABSTRACT FROM AUTHOR]

Background: Developing effective strategies for reducing dementia risk requires a detailed understanding of the risk and protective factors associated with the progression of mild cognitive impairment (MCI) to dementia. Objective: We aimed to systematically review the evidence for sex differences in these factors. Methods: Five online databases (PubMed/CINAHL/EMBASE/PsycINFO/Cochrane) were searched from inception until 17 October 2022 for cohort studies that focused on sex differences in risk and protective factors in the progression of MCI to dementia. Results: A total of 2,972 studies were identified, of which 12 studies from five countries were included in the systematic review. There was substantial variability in study designs, study populations and outcome measures. Sex differences were present in the associations of sociodemographic, health, psychological factors, genetic and other biomarkers with the progression of MCI to dementia. APOE ɛ4 status and depression appeared to increase the risk of progression for females, whereas history of stroke, MRI markers and cerebrospinal fluid biomarkers appeared to increase the risk of progression for males. APOE ɛ2 status and marital status (unmarried) were observed to reduce risk of progression in males and females, respectively. Conclusions: The ability of studies to accurately detail risk factors for dementia are likely limited when solely controlling for the effects of sex. Although the heterogeneity and underpowered nature of the studies made it difficult to synthesize the findings for each risk factor, this study highlights the apparent need for further research examining risk factors for dementia in males and females with MCI separately. [ABSTRACT FROM AUTHOR]

Objective: To optimise dementia prevention strategies, we must understand the complex relationships between lifestyle behaviours, frailty and genetics.Methods: We explored relationships between frailty index, healthy lifestyle and polygenic risk scores (all assessed at study entry) and incident all-cause dementia as recorded on hospital admission records and death register data.Results: The analytical sample had a mean age of 64.1 years at baseline (SD=2.9) and 53% were women. Incident dementia was detected in 1762 participants (median follow-up time=8.0 years). High frailty was associated with increased dementia risk independently of genetic risk (HR 3.68, 95% CI 3.11 to 4.35). Frailty mediated 44% of the relationship between healthy lifestyle behaviours and dementia risk (indirect effect HR 0.95, 95% CI 0.95 to 0.96). Participants at high genetic risk and with high frailty had 5.8 times greater risk of incident dementia compared with those at low genetic risk and with low frailty (HR 5.81, 95% CI 4.01 to 8.42). Higher genetic risk was most influential in those with low frailty (HR 1.31, 95% CI 1.22 to 1.40) but not influential in those with high frailty (HR 1.09, 95% CI 0.92 to 1.28).Conclusion: Frailty is strongly associated with dementia risk and affects the risk attributable to genetic factors. Frailty should be considered an important modifiable risk factor for dementia and a target for dementia prevention strategies, even among people at high genetic risk. [ABSTRACT FROM AUTHOR]

Objective: To determine whether health-deficit accumulation is associated with the risks of mild cognitive impairment (MCI) and dementia independently of APOE genotype.Methods: A frailty index was calculated using the deficit-accumulation approach in participants aged 50 years and older from the National Alzheimer's Coordinating Center. Cognitive status was determined by clinical evaluation. Using multistate transition models, we assessed the extent to which an increasing degree of frailty affected the probabilities of transitioning between not cognitively impaired (NCI), MCI, and dementia.Results: Participants (n=14 490) had a mean age of 72.2 years (SD=8.9 years; range=50-103 years). Among those NCI at baseline (n=9773), each 0.1 increment increase in the frailty index was associated with a higher risk of developing MCI and a higher risk of progressing to dementia. Among those with MCI at baseline (n=4717), higher frailty was associated with a higher risk of progressing to dementia, a lower probability of being reclassified as NCI, and a higher likelihood of returning to MCI in those that were reclassified as NCI. These risk effects were present and similar in both carriers and non-carriers of the APOE ε4 allele.Conclusion: Among older Americans, health-deficit accumulation affects the likelihood of progressive cognitive impairment and the likelihood of cognitive improvement independently of a strong genetic risk factor for dementia. Frailty represents an important risk factor for cognitive dysfunction and a marker of potential prognostic value. [ABSTRACT FROM AUTHOR]

Cognitive reserve (CR) is a theoretical construct describing the underlying cognitive capacity of an individual that confers differential levels of resistance to, and recovery from, brain injuries of various types. To date, estimates of an individual's level of CR have been based on single proxy measures that are retrospective and static in nature. To develop a measure of dynamic change in CR across a lifetime, we previously identified a latent factor, derived from an exploratory factor analysis of a large sample of healthy older adults, as current CR (cCR). In the present study, we examined the longitudinal results of a sample of 272 older adults enrolled in the Tasmanian Healthy Brain Project. Using results from 12-month and 24-month reassessments, we examined the longitudinal validity of the cCR factor using confirmatory factor analyses. The results of these analyses indicate that the cCR factor structure is longitudinally stable. These results, in conjunction with recent results from our group demonstrating dynamic increases in cCR over time in older adults undertaking further education, lend weight to this cCR measure being a valid estimate of dynamic change in CR over time. [ABSTRACT FROM AUTHOR]

The transfer impedances of current transducers are estimated using a special calibration fixture, which is often assumed to be perfectly matched at its coaxial ports. However, the errors inherent in this approximation increase with frequency, making the measurement of cable currents increasingly inaccurate at higher frequencies. A one-dimensional (1-D) transmission line model is proposed to account for such errors in a calibration fixture of simple design by using additional measurements to quantify the mismatches in the system. This technique is validated using a numerical model of such a calibration fixture as well against experimental data and numerical predictions for the current induced on a wire inside a rectangular cavity due to an external source that is coupled into the interior via an aperture. It is concluded that the proposed approach provides improved results with a calibration fixture of simple design for frequencies up to at least 600 MHz. Index Terms--Calibration, current measurement, electronic analysis, electromagnetic compatibility (EMC), electromagnetic measurements, scattering parameters, transmission line matrix methods, transmission line theory.