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Royall DR, Palmer RF. A δ Homolog for Dementia Case Finding with Replication in the Alzheimer's Disease Neuroimaging Initiative. J Alzheimers Dis 2019; 67:67-79. [PMID: 30507569 DOI: 10.3233/jad-171053] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Dementia can be empirically described by the latent dementia phenotype "δ" and its various composite "homologs". We have explored δ's blood-based protein biomarkers in the Texas Alzheimer's Research and Care Consortium (TARCC) study. However, it would be convenient to replicate those associations in the Alzheimer's Disease Neuroimaging Initiative (ADNI). To this end, we have engineered a δ homolog from observed cognitive performance measures common to both projects. Our findings were replicated in randomly selected 50% splits of TARCC data (Group 1, N = 1,747; Group 2, N = 1,755), and then independently in ADNI (N = 1,737). The new δ homolog, i.e., "dT2A" (d-TARCC to ADNI), fit the data of both studies well, and was strongly correlated with dementia severity, as rated by the Clinical Dementia Rating Scale "sum of boxes" (TARCC: r = 0.99, p < 0.001; ADNI: r = 0.96, p < 0.001). dT2A achieved an area under the receiver operating characteristic curve of 0.981 (0.976-0.985) for the discrimination of Alzheimer's disease from normal controls in TARCC, and 0.988 (0.983-0.993) in ADNI. dT2A is the 12th δ homolog published to date, and opens the door to independent replications across these and similar studies.
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Affiliation(s)
- Donald R Royall
- Department of Psychiatry, The University of Texas Health Science Center, San Antonio, TX, USA
- Department of Medicine, The University of Texas Health Science Center, San Antonio, TX, USA
- Department of Family and Community Medicine, The University of Texas Health Science Center, San Antonio, TX, USA
- South Texas Veterans' Health System Audie L. Murphy Division GRECC, San Antonio, TX, USA
| | - Raymond F Palmer
- Department of Family and Community Medicine, The University of Texas Health Science Center, San Antonio, TX, USA
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Royall DR, Palmer RF. δ Scores Identify Subsets of "Mild Cognitive Impairment" with Variable Conversion Risks. J Alzheimers Dis 2019; 70:199-210. [PMID: 31127788 DOI: 10.3233/jad-190266] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND The latent variable "δ" (for "dementia) is a transdiagnostic measure of dementia severity. δ can be reified and applied to individuals as a composite "d-score". Like Spearman's general intelligence factor "g", δ can be constructed from almost any cognitive battery. So many are available that we must further distinguish each composite as a δ "homolog". Fourteen have been validated. All are strongly associated with dementia severity and potentially with mild cognitive impairment (MCI) conversion. OBJECTIVES To assess δ's impact on MCI conversion risk. METHODS A new δ homolog (dDx) was constructed in 1,230 Mexican-American (MA) and 2,215 non-Hispanic White (NHW) participants in the Texas Alzheimer's Research and Care Consortium (TARCC). 1,445 normal controls (NC) and 723 MCI were followed annually for up to 6 years. RESULTS Each SD decrease in the dDx score increased the risk of conversion sixteen-fold [OR = 16.39 (CI: 5.0-52.6)]. Cases below the optimal diagnostic threshold for Alzheimer's disease (AD) versus NC were labeled as having a functionally salient cognitive impairment (FSCI). Such cases were at a 73-fold increase risk of a diagnosis of AD [OR = 73.19 (95% CI: 58.3-92.0)]. However, 25.6% of MCI cases were also FSCI(+). They accounted disproportionately for prospective conversions. Age <80 years, the absence of an ɛ4 allele, <12 years of education, and MA ethnicity independently increased the risk of diagnosing FSCI as MCI. CONCLUSION A sizable minority of MCI cases may be misdiagnosed and they account disproportionately for AD conversions.
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Affiliation(s)
- Donald R Royall
- Departments of Psychiatry, The University of Texas Health Science Center, San Antonio, TX, USA
- Departments of Medicine, The University of Texas Health Science Center, San Antonio, TX, USA
- Departments of Family and Community Medicine, the University of Texas Health Science Center, San Antonio, TX, USA
- South Texas Veterans' Health System Audie L. Murphy Division GRECC, San Antonio, TX, USA
| | - Raymond F Palmer
- Departments of Family and Community Medicine, the University of Texas Health Science Center, San Antonio, TX, USA
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Royall DR, Palmer RF, Markides KS. Exportation and Validation of Latent Constructs for Dementia Case Finding in a Mexican American Population-based Cohort. J Gerontol B Psychol Sci Soc Sci 2017; 72:947-955. [PMID: 26968639 PMCID: PMC5927021 DOI: 10.1093/geronb/gbw004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 01/11/2016] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND The latent variable "δ" has been validated as a dementia phenotype. δ can be extracted from Spearman's general intelligence factor "g" in any data set that contains measures of cognition and instrumental activities of daily living (IADL). We used δ composites ("d-scores") to estimate the prevalence of dementia in the Hispanic Established Population for Epidemiological Studies in the Elderly (H-EPESE). METHOD δ was constructed from Mini-Mental State Examination, a clock-drawing task (CLOX), and IADL. δ's H-EPESE factor weights were validated in the well-characterized Texas Alzheimer's Research and Care Consortium (TARCC). Optimal thresholds for the discrimination between "Alzheimer's disease" (AD) versus normal controls (NCs) were determined by receiver operating characteristic curve. Those thresholds were used to estimate the prevalence of dementia in H-EPESE. RESULTS Each δ homolog fits its source's data well. d-scores were strongly associated with Clinical Dementia Rating scale Sum of Boxes (r = .74-.85, all p < .001], and accurately distinguished AD cases from NCs, in both Mexican Americans (MAs) and non-Hispanic Whites (NHWs) [c = 0.94-0.96]. The TARCC MA threshold estimated the prevalence of dementia at 21.4% in H-EPESE. The NHW threshold estimated the prevalence of dementia at 21.0%. CONCLUSIONS It is possible to export δ composites from populations to well-characterized cohorts for validation.
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Affiliation(s)
- Donald R Royall
- Department of Psychiatry, University of Texas Health Science Center, San Antonio
- Audie L. Murphy Division GRECC, South Texas Veterans’ Health System, San Antonio
- Department of Family and Community Medicine, University of Texas Health Science Center, San Antonio
| | - Raymond F Palmer
- Department of Family and Community Medicine, University of Texas Health Science Center, San Antonio
| | - Kyriakos S Markides
- Division of Social and Behavioral Sciences, Department of Preventive Medicine and Community Health, University of Texas Medical Branch, Galveston
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Royall DR, Al-Rubaye S, Bishnoi R, Palmer RF. Serum proteins mediate depression's association with dementia. PLoS One 2017; 12:e0175790. [PMID: 28594820 PMCID: PMC5464526 DOI: 10.1371/journal.pone.0175790] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 03/31/2017] [Indexed: 01/08/2023] Open
Abstract
The latent variable "δ" (for "dementia") uniquely explains dementia severity. Depressive symptoms are independent predictors of δ. We explored 115 serum proteins as potential causal mediators of the effect of depressive symptoms on δ in a large, ethnically diverse, longitudinal cohort. All models were adjusted for age, apolipoprotein E, education, ethnicity, gender, hemoglobin A1c, and homocysteine, and replicated in randomly selected 50% subsets. Alpha1-antitrypsin (A1AT), FAS, Heparin-binding EGF-like Growth Factor (HB-EGF), Insulin-like Growth Factor-1 (IGF-1), Luteinizing Hormone (LH), Macrophage Inflammatory Protein type 1 alpha (MIP-1α), Resitin, S100b, Tissue Inhibitor of Metalloproteinase type 1 (TIMP-1), and Vascular Cell Adhesion Molecule type 1 (VCAM-1) each were partial mediators of depression's association with δ. These proteins may offer targets for the treatment of depression's specific effect on dementia severity and Alzheimer's Disease (AD) conversion risk.
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Affiliation(s)
- Donald R. Royall
- Department of Psychiatry, the University of Texas Health Science Center, San Antonio, Texas, United States of America
- Department of Medicine, the University of Texas Health Science Center, San Antonio, Texas, United States of America
- Department of Family and Community Medicine, the University of Texas Health Science Center, San Antonio, Texas, United States of America
- South Texas Veterans’ Health System Audie L. Murphy Division Geriatric Research Education and Clinical Care Center, San Antonio, Texas, United States of America
| | - Safa Al-Rubaye
- Department of Psychiatry, the University of Texas Health Science Center, San Antonio, Texas, United States of America
| | - Ram Bishnoi
- Department of Psychiatry, the Medical College of Georgia, Augusta, Georgia, United States of America
| | - Raymond F. Palmer
- Department of Family and Community Medicine, the University of Texas Health Science Center, San Antonio, Texas, United States of America
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Peh CX, Abdin E, Vaingankar JA, Verma S, Chua BY, Sagayadevan V, Seow E, Zhang Y, Shahwan S, Ng LL, Prince M, Chong SA, Subramaniam M. Validation of a Latent Construct for Dementia in a Population-Wide Dataset from Singapore. J Alzheimers Dis 2016; 55:823-833. [PMID: 27802230 DOI: 10.3233/jad-160575] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND The latent variable δ has been proposed as a proxy for dementia. Previous validation studies have been conducted using convenience samples. It is currently unknown how δ performs in population-wide data. OBJECTIVE To validate δ in Singapore using population-wide epidemiological study data on persons aged 60 and above. METHODS δ was constructed using items from the Community Screening Instrument for Dementia (CSI'D) and World Health Organization Disability Assessment Schedule (WHODAS II). Confirmatory factor analysis (CFA) was conducted to examine δ model fit. Convergent validity was examined with the Clinical Dementia Rating scale (CDR) and GMS-AGECAT dementia. Divergent validity was examined with GMS-AGECAT depression. RESULTS The δ model demonstrated fit to the data, χ2(df) = 249.71(55), p < 0.001, CFI = 0.990, TLI = 0.997, RMSEA = 0.037. Latent variable δ was significantly associated with CDR and GMS-AGECAT dementia (range: β= 0.32 to 0.63), and was not associated with GMS-AGECAT depression. Compared to unadjusted models, δ model fit was poor when adjusted for age, gender, ethnicity, and education. CONCLUSION The study found some support for δ as a proxy for dementia in Singapore based on population data. Both convergent and divergent validity were established. In addition, the δ model structure appeared to be influenced by age, gender, ethnicity, and education covariates.
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Affiliation(s)
- Chao Xu Peh
- Research Division, Institute of Mental Health, Singapore, Singapore
| | - Edimansyah Abdin
- Research Division, Institute of Mental Health, Singapore, Singapore
| | | | - Swapna Verma
- Early Psychosis Intervention Programme, Institute of Mental Health, Singapore, Singapore
| | - Boon Yiang Chua
- Research Division, Institute of Mental Health, Singapore, Singapore
| | | | - Esmond Seow
- Research Division, Institute of Mental Health, Singapore, Singapore
| | - YunJue Zhang
- Research Division, Institute of Mental Health, Singapore, Singapore
| | - Shazana Shahwan
- Research Division, Institute of Mental Health, Singapore, Singapore
| | - Li Ling Ng
- Department of Psychological Medicine, Changi General Hospital, Singapore, Singapore
| | - Martin Prince
- Health Service and Population Research Department, Institute of Psychiatry, Psychology & Neuroscience, King's College London, United Kingdom
| | - Siow Ann Chong
- Research Division, Institute of Mental Health, Singapore, Singapore
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Abstract
The latent variable "δ" (for "dementia") has been proposed as a phenotype for all cause dementia. δ is extracted from cognitive batteries by a specific confirmatory factor analysis in a structural equation modeling framework. δ appears to be uniquely responsible for cognition's association with functional status. Because it is extracted from Spearman's general intelligence factor "g", this has broad implications for dementia's assessment and pathophysiology. This issue of the Journal of Alzheimer's Disease brings together several demonstrations of δ's psychometric properties by investigative groups from three continents. In their aggregate, they suggest that δ homologs may have far ranging applications in dementia's clinical assessment and biomarker selection.
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Affiliation(s)
- Donald R Royall
- Departments of Psychiatry, Family and Community Medicine, The University of Texas Health Science Center, San Antonio, TX, USA
- South Texas Veterans' Health System, Audie L. Murphy Division GRECC, San Antonio, TX, USA
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