Year: 2019
Type: article
Abstract: A variety of dementia indicators have been proposed in lieu of clinical diagnoses, ranging from cutoff scores on a cognitive screening measure such as MMSE to weighted combinations of cognitive test scores. Latent variable dementia indicators, “delta” (δ), are reliable predictors of dementia risk (Gavett et al., Peh et al., Royall & Palmer). δ reflects variance in a set of cognitive and functional ability indicators beyond variance already accounted for by a g’ factor solely indicated by cognitive scores. We built on this approach in a sample where clinical diagnoses were available for testing the validity of δ. Further, we used the twin sample to derive the genetic correlation between δ and clinical diagnosis. We used confirmatory factor analysis to derive δ and general cognitive ability residual (g’) scores for 1,471 individuals (39% demented) from the Study of Dementia in Swedish Twins (HARMONY). Functional ability and memory loaded onto δ, but not g’. We fit a bivariate Cholesky model to 631 twin pairs (249 MZ; 382 DZ) to construct the genetic correlation between δ and clinical diagnosis. Delta more strongly correlated with dementia diagnoses than did g’ (r = −.78 vs. r = −.12). The genetic correlation between δ and clinical diagnosis was −.77 (SE = .14, p < .001). A latent dementia factor, comprised of memory, functional ability, and cognitive functioning has more predictive validity for dementia risk compared with a residual general cognitive ability factor. The same genetic sources of variance strongly contribute to both δ and clinical diagnosis. Genetic influences underlying dementia account for approximately 60% of genetic variance in δ. This approach provides a way to reconcile studies that use varying measures of cognitive, functional, and memory abilities. Results advance the conceptualization of a latent dementia model in differentiating g’ to represent a unique cognitive ability factor, from δ as a construct that strongly overlaps with dementia risk. This study highlights the utility of a continuous dementia construct that provides greater power and variance to test genetic models than dichotomous clinical diagnoses or dichotomous indicators. Funding: NIH Grant No. R01 AG060470.
Source: Alzheimer s & Dementia
Language: English
Subfield: Psychiatry and Mental health
Field: Medicine
Domain: Health Sciences
Open Access status: bronze
OpenAlex ID: W2980388730