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- Womack, Sean R., et al.
(författare)
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Genetic and Environmental Correlates of the Nonlinear Recovery of Cognitive Ability in Twins
- 2022
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Ingår i: Developmental Psychology. - : American Psychological Association (APA). - 0012-1649 .- 1939-0599. ; 58:3, s. 535-550
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Tidskriftsartikel (refereegranskat)abstract
- Twins regularly score nearly a standard deviation below the population mean on standardized measures of cognitive development in infancy but recover to the population mean by early childhood, making rapid gains through the toddler years. To date, only polynomial growth models have been fit to model cognitive recovery across childhood, limiting the applicability of the growth parameters to later developmental periods. We fit a nonlinear asymptotic Gompertz growth model to prospective cognitive scores from 1,153 individual twins from 578 families (47.9% male, 91.5% White, 61.6% monozygotic) measured at 16 time points between 3 months and 15 years. Twins displayed a lower asymptote of 86.47 (.90 SD below the population mean) and gained on average 17.01 points, achieving an upper asymptote of 103.48. Growth was observed to be most rapid at 3.26 years, highlighting the importance of the toddler years in cognitive development. Biometric analyses revealed that shared environmental factors accounted for the majority of the variance in initial cognitive ability as well as asymptotic growth in cognitive ability. Gestational age and family socioeconomic status (SES) were robust predictors of cognitive growth. Results from the present study provide insight into the growth processes underlying the recovery of cognitive ability to the population mean for children evincing slight delays in their initial cognitive ability. In particular, findings highlight prenatal factors and family economic resources as important aspects of the environment in the recovery of cognitive ability.
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- Beam, Christopher R., et al.
(författare)
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Estimating Likelihood of Dementia in the Absence of Diagnostic Data : A Latent Dementia Index in 10 Genetically Informed Studies
- 2022
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Ingår i: Journal of Alzheimer's Disease. - : IOS Press. - 1387-2877 .- 1875-8908. ; 90:3, s. 1187-1201
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Epidemiological research on dementia is hampered by differences across studies in how dementia is classified, especially where clinical diagnoses of dementia may not be available. OBJECTIVE: We apply structural equation modeling to estimate dementia likelihood across heterogeneous samples within a multi-study consortium and use the twin design of the sample to validate the results. METHODS: Using 10 twin studies, we implement a latent variable approach that aligns different tests available in each study to assess cognitive, memory, and functional ability. The model separates general cognitive ability from components indicative of dementia. We examine the validity of this continuous latent dementia index (LDI). We then identify cut-off points along the LDI distributions in each study and align them across studies to distinguish individuals with and without probable dementia. Finally, we validate the LDI by determining its heritability and estimating genetic and environmental correlations between the LDI and clinically diagnosed dementia where available. RESULTS: Results indicate that coordinated estimation of LDI across 10 studies has validity against clinically diagnosed dementia. The LDI can be fit to heterogeneous sets of memory, other cognitive, and functional ability variables to extract a score reflective of likelihood of dementia that can be interpreted similarly across studies despite diverse study designs and sampling characteristics. Finally, the same genetic sources of variance strongly contribute to both the LDI and clinical diagnosis. CONCLUSION: This latent dementia indicator approach may serve as a model for other research consortia confronted with similar data integration challenges.
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- Beam, Christopher R., et al.
(författare)
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Midlife study of the Louisville Twins : Connecting cognitive development to biological and cognitive aging
- 2020
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Ingår i: Behavior Genetics. - : Springer. - 0001-8244 .- 1573-3297. ; 50:2, s. 73-83
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Tidskriftsartikel (refereegranskat)abstract
- The Louisville Twin Study (LTS) began in 1958 and became a premier longitudinal twin study of cognitive development. The LTS continuously collected data from twins through 2000 after which the study closed indefinitely due to lack of funding. Now that the majority of the sample is age 40 or older (61.36%, N = 1770), the LTS childhood data can be linked to midlife cognitive functioning, among other physical, biological, social, and psychiatric outcomes. We report results from two pilot studies in anticipation of beginning the midlife phase of the LTS. The first pilot study was a participant tracking study, in which we showed that approximately 90% of the Louisville families randomly sampled (N = 203) for the study could be found. The second pilot study consisted of 40 in-person interviews in which twins completed cognitive, memory, biometric, and functional ability measures. The main purpose of the second study was to correlate midlife measures of cognitive functioning to a measure of biological age, which is an alternative index to chronological age that quantifies age as a function of the breakdown of structural and functional physiological systems, and then to relate both of these measures to twins’ cognitive developmental trajectories. Midlife IQ was uncorrelated with biological age (−.01) while better scores on episodic memory more strongly correlated with lower biological age (−.19 to −.31). As expected, midlife IQ positively correlated with IQ measures collected throughout childhood and adolescence. Additionally, positive linear rates of change in FSIQ scores in childhood significantly correlated with biological age (−.68), physical functioning (.71), and functional ability (−.55), suggesting that cognitive development predicts lower biological age, better physical functioning, and better functional ability. In sum, the Louisville twins can be relocated to investigate whether and how early and midlife cognitive and physical health factors contribute to cognitive aging.
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- Luo, Jing, et al.
(författare)
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Dementia risk in women higher in same-sex than opposite-sex twins
- 2020
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Ingår i: Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring. - : John Wiley & Sons. - 2352-8729. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- IntroductionHormones may be one possible mechanism underlying sex differences in dementia incidence. We examined whether presumed differential prenatal hormone milieu is related to dementia risk by comparing dementia rates in same- and opposite-sex dizygotic twin pairs in male and female twins.MethodsThe sample comprised 43,254 individuals from dizygotic twin pairs aged 60 and older from the Swedish Twin Registry. Survival analyses were conducted separately for females and males.ResultsFemale twins from opposite-sex pairs had significantly lower dementia risk than female twins from same-sex pairs, but the differences emerged only after age 70 (hazard ratio = 0.64, P = 0.004). Results were not explained by postnatal risk factors for dementia, and no interaction between twin type and apolipoprotein E (APOE) epsilon 4 was found. Male twins from same-sex versus opposite-sex pairs did not differ significantly.DiscussionThe results suggest that relatively masculine prenatal hormone milieus correlate with lower dementia risk in females.
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