Publications (63) View all
-
Article: Getting Past "g": testing a new model of dementing processes in persons without dementia.
[show abstract] [hide abstract]
ABSTRACT: The cognitive correlates of functional status are essential to dementia case-finding. The authors have used structural-equation models to explicitly distinguish dementia-relevant variance in cognitive task performance (i.e., δ) from the variance that is unrelated to a dementing process (i.e., g'). Together, g' and δ comprise Spearman's "g." Although δ represents only a small fraction of the total variance in cognitive task performance, it is more strongly associated with dementia severity than is g'. In this analysis, the authors test whether δ can predict future cognitive decline in persons clinically without dementia at baseline. These results have implications for the clinical assessment of dementia and suggest that functional status should assume a more important role.The Journal of neuropsychiatry and clinical neurosciences 12/2012; 24(1):37-46. · 2.34 Impact Factor -
Article: The role of physical activity and diabetes status as a moderator: functional disability among older Mexican Americans.
[show abstract] [hide abstract]
ABSTRACT: Purpose: we investigate the temporal association between the rate of change in physical function and the rate of change in disability across four comparison groups: Those with and without diabetes who report >30 min of physical activity per day, and those who report <30 min of physical activity per day. six waves of longitudinal data from the Hispanic Established Population for Epidemiologic Studies of the Elderly were utilised. At baseline, there were a total of 3,050 elder participants aged 65 years old or greater. The longitudinal rates of change in disability and physical function were compared by the diabetes status (ever versus none) and the physical activity status (less than or greater than or equal to 30 min per day). disability and physical function data were analysed using a latent growth curve modelling approach adjusted for relevant demographic/health-related covariates. There were statistically significant longitudinal declines in physical function and disability (P < 0.001) in all groups. Most notable, the physical activity status was an important moderator. Those with >30 min of activity demonstrated better baseline function and less disability as well as better temporal trajectories than those reporting <30 min of physical activity per day. Comparisons between diabetes statuses within the same physical activity groups showed worse disability trajectories among those with diabetes. a longitudinal decline in physical function and disability is moderated most notably by physical activity. The diabetes status further moderates decline in function and disability over time. Increased physical activity appears to be protective of disability in general and may lessen the influence of diabetes-related disability in older Mexican Americans, particularly at the end of life.Age and Ageing 10/2012; 41(6):752-8. · 3.09 Impact Factor -
Article: Estimating the temporal evolution of Alzheimer's disease pathology with autopsy data.
[show abstract] [hide abstract]
ABSTRACT: The temporal growth of Alzheimer's disease (AD) neuropathology cannot be easily determined because autopsy data are available only after death. We combined autopsy data from 471 participants in the Honolulu-Asia Aging Study (HAAS) into latent factor measures of neurofibrillary tangle and neuritic plaque counts. These were associated with intercept and slope parameters from a latent growth curve (LGC) model of 9-year change in cognitive test performance in 3244 autopsied and non-autopsied HAAS participants. Change in cognition fully mediated the association between baseline cognitive performance and AD lesions counts. The mediation effect of cognitive change on both AD lesion models effectively dates them within the period of cognitive surveillance. Additional analyses could lead to an improved understanding of lesion propagation in AD.Journal of Alzheimer's disease: JAD 06/2012; 32(1):23-32. · 3.74 Impact Factor -
Article: Validation of a latent variable representing the dementing process.
[show abstract] [hide abstract]
ABSTRACT: The cognitive correlates of functional status are essential to dementia case-finding. Nevertheless, cognitive performance is a generally weak predictor of functional outcomes. We have employed structural equation models to explicitly distinguish functional status, and therefore "dementia-relevant" variance in cognitive task performance (i.e., δ) from the variance that is unrelated to a dementing process (i.e., g'). Together, g' + δ encompass Spearman's g. Although δ represents only a small fraction of the total variance in cognitive task performance, it is more strongly associated with dementia status than is g'. In this study, we validate δ in a well characterized Alzheimer's disease cohort, the Texas Alzheimer's Research and Care Consortium. Our approach results in "error free" continuous variables. This suggests that δ can serve as a dementia specific endophenotype. As a result, future studies may be able to associate δ with inflammatory and genetic biomarkers.Journal of Alzheimer's disease: JAD 03/2012; 30(3):639-49. · 3.74 Impact Factor -
Article: Modeling regional vulnerability to Alzheimer pathology.
[show abstract] [hide abstract]
ABSTRACT: Latent growth curve (LGC) models estimate change over time in a cohort's serially obtained measurements. We have applied LGC techniques to a spatial distribution of Alzheimer's disease (AD) pathology using autopsy data from 435 participants in the Honolulu-Asia Aging Study. Neurofibrillary tangle (NFT) and neuritic plaques (NP) were distributed across differently ordered sets of anatomical regions. The gradient of spatial change in neuritic plaque (dNP), was significantly associated with that of neurofibrillary tangle (dNFT), but weakly and inversely (r = -0.12; p < 0.001). Both dNFT and dNP correlated significantly and inversely with Braak stage. Sixty-one percent of the variance in Braak stage was explained by dNFT independent of covariates. Only dNFT was significantly associated with longitudinal change in cognition. Only dNP was associated with apolipoprotein (APOE) e4 burden. This is the first application of LGC models to spatially-ordered data. The result is a quantification of the interindividual variation in the interregional vulnerability to Alzheimer's disease lesions.Neurobiology of aging 07/2011; 33(8):1556-63. · 5.94 Impact Factor
