Profiles of Cognitive Functioning in a Population-Based Sample of Centenarians Using Factor Mixture Analysis

Abstract

Background/Study Context: The goal of the study was to identify and characterize latent profiles (clusters) of cognitive functioning in centenarians and the psychometric properties of cognitive measures within them.

Methods: Data were collected from cross-sectional, population-based sample of 244 centenarians (aged 98 to 108, 15.8% men, 20.5% African American, 38.0% community-dwelling) from 44 counties in northern Georgia participating in the Georgia Centenarian Study (2001–2008). Measures included the Mini-Mental State Examination (MMSE), Severe Impairment Battery (SIB), Wechsler Adult Intelligence Scale-III Similarities subtest (WAIS), Hand Tapping, Behavioral Dyscontrol Scale (BDS), Controlled Oral Word Association Test (COWAT), and Fuld Object Memory Evaluation (FOME). The Global Deterioration Rating Scale (GDRS) was used to independently evaluate criterion-related validity for distinguishing cognitively normal and impaired groups. Relevant covariates included directly assessed functional status for basic and instrumental activities of daily living (DAFS), race, gender, educational attainment, Geriatric Depression Scale Short Form (GDS), and vision and hearing problems.

Results: Results suggest two distinct classes of cognitive performance in this centenarian sample. Approximately one third of the centenarians show a pattern of markedly lower cognitive performance on most measures. Group membership is independently well predicted (area under the curve [AUC] = .83) by GDRS scores (sensitivity 67.7%, specificity 82.4%). Membership in the lower cognitive performance group was more likely for individuals who were older, African Americans, had more depressive symptoms, lower plasma folate, carriers of the apolipoprotein E (APOE) ε4 allele, facility residents, and individuals who died in the 2 years following interview.

Conclusions: In a population expected to have high prevalence of dementia, latent subtypes can be distinguished via factor mixture analysis that provide normative values for cognitive functioning. The present study allows estimates for normative cognitive performance in this age group.

Acknowledgments

The GCS was funded by the National Institute on Aging, P01AG17553 (2001–2008). Davey was supported by PENR-2008-05011, PENR-2010-04643, R21CA158877, R01CA158361, and R01AG13180. Dai was supported by NSF-REESE-0814901. Green was supported by NIH grants HG02213 and AG027841. Two of the authors (S.P.S. and R.H.A.) and the University of Colorado hold patents on the use of assays for total homocysteine and other metabolites to diagnose vitamin B12 and folate deficiencies, and a company has been formed at the University of Colorado to perform such assays. The Georgia Centenarian Study includes S. M. Jazwinski (Tulane University), Maurice MacDonald (Kansas State University), M. Gearing (Emory University), W. R. Markesbery (University of Kentucky, deceased), W. L. Rodgers (University of Michigan), and J. Arnold (University of Georgia). The authors acknowledge the valuable recruitment and data acquisition effort from M. Burgess, K. Grier, E. Jackson, E. McCarthy, K. Shaw, L. Strong, and S. Reynolds, data acquisition team manager; S. Anderson, E. Cassidy, M. Janke, and J. Savla, data management; and M. Poon for project fiscal management, all of the University of Georgia.

Notes

Note. GDS-SF = Geriatric Depression Scale Short Form; DAFS BADLs = directly assessed functional status basic activities of daily living; DAFS IADLs = directly assessed functional status instrumental activities of daily living.

^a t test with equal variances.

^b Fisher's exact test.

^c t test with unequal variances.

Note. MMSE = Mini-Mental State Examination; SIB = Severe Impairment Battery; WAIS = Wechsler Adult Intelligence Scale; Handtaps = modified Halstead-Reitan Hand Tapping test; BDS = Behavioral Dyscontrol Scale; FOME = Fuld Object Memory Evaluation.

Note. DAFS BADLs = directly assessed functional status basic activities of daily living; DAFS IADLs = directly assessed functional status instrumental activities of daily living; MMSE = Mini-Mental State Examination; SIB = Severe Impairment Battery; WAIS = Wechsler Adult Intelligence Scale; Handtaps = modified Halstead-Reitan Hand Tapping test; BDS = Behavioral Dyscontrol Scale; FOME = Fuld Object Memory Evaluation.

Bayesian likelihood-ratio test (26 df) = 647.5, p < .001.

Note. GDS-SF = Geriatric Depression Scale Short Form.

Note. GDRS = Global Deterioration Rating Scale; DAFS BADLs = directly assessed functional status basic activities of daily living; DAFS IADLs = directly assessed functional status instrumental activities of daily living.

Note. Fisher's exact test, p < .001.