Twin samples allow to conduct a quasi-experimental co-twin case–control approach that can control for genetic and environmental confounding in brain–cognition associations, being more informative on causality compared with studies in unrelated individuals. We conducted a review of studies that have utilized discordant co-twin design to investigate the associations of brain imaging markers of Alzheimer's disease and cognition. Inclusion criteria encompassed twin pairs discordant for cognition or Alzheimer's disease imaging markers and reporting of within-twin pair comparison on the association between cognition and brain measures. Our PubMed search (2022 April 23, updated 2023 March 9) resulted in 18 studies matching these criteria. Alzheimer's disease imaging markers have been addressed only by few studies, most with small sample size. Structural magnetic resonance imaging studies have indicated greater hippocampal volume and thicker cortex in co-twins with better cognitive performance compared with their co-twins with poorer cognitive performance. No studies have looked at cortical surface area. Positron emission tomography imaging studies have suggested that lower cortical glucose metabolism rate and higher cortical neuroinflammation, amyloid, and tau accumulations are related to poorer episodic memory in within-twin pair comparisons. Thus far, only cross-sectional within-twin pair associations of cortical amyloid and hippocampal volume with cognition have been replicated.
Background: Center for Epidemiological Studies-Depression scale (CES-D) is widely used self-report measure for assessing depressive symptoms. However, few studies have formally assessed whether the CES-D and its short forms can be used to compare scores in cognitively unimpaired versus cognitively impaired persons and across different age cohorts in old age. We examined the factor structures of 20-, 15-, and 8-item CES-D scales and their measurement invariance for cognitive status and age and associations with cohort, cognitive impairment, and genetic risk of depression.Methods: Participants were from a population-based older Finnish Twin Cohort study including 71–79-year-olds from the MEMTWIN II (n=1698) and 90+ year-olds from the NONAGINTA (n=134) sub-studies. Exploratory factor analyses were performed in MEMTWIN II and confirmatory factor analyses in both cohorts. Cognitive status comparisons and associations with polygenic risk score of major depressive disorder (MDD-PRS) were conducted in MEMTWIN II. Cohort comparisons were performed between MEMTWIN II and NONAGINTA.Results: Exploratory factor analyses (n=1034) suggested four- (CES-D 20) and three-factor (CES-D 8) structures and these models fit the data well in confirmatory analyses (n=664). Unidimensional models had a good (CES-D 15 & 20) or fair fit (CES-D 8). Measurement invariance testing supported scalar invariance of all CES-D versions for cognitive status and age. NONAGINTA participants had significantly more depressive symptoms than MEMTWIN II participants. Higher MDD-PRS was significantly associated with more depressive symptoms in different CES-D versions.Discussion: The measurement properties of the CES-D indicate that different versions are measuring depressive symptoms similarly across the cohorts and cognitive spectrum in old age. Thus, even the short CES-D appears to be a psychometrically adequate tool to assess depressive symptoms in old age including those over 90 years old and those with cognitive impairment. Higher MDD-PRS and older age predicted greater depressive symptoms in old age.
BackgroundSeveral risk and protective factors of dementia are known, but the importance of genetic and environmental influences and the antecedents of cognitive functioning in 90‐year‐olds are not well known. Genetic and environmental confounding can be controlled better by using family data compared to samples of unrelated individuals. We examined dementia risk factors in 90‐year‐olds by conducting a case‐control co‐twin study on the associations of physical and psychological well‐being with episodic memory (EM).MethodWe invited 90‐year‐old twins from a population‐based older Finnish Twin Cohort study to participate in the ongoing NONAGINTA –study that includes questionnaires (risk factors) and telephone interview (cognitive functioning). To date, eight full same‐sex pairs have cognitive data available (6 female, 6 monozygotic). We calculated a risk score for each twin and co‐twin, based on the following factors: depressive symptoms (measured with the Center for Epidemiological Studies – Depression, CES‐D), body mass index (BMI), physical activity (MET hours), life satisfaction, neuroticism, and years of education. Within each twin pair, co‐twins were assigned as having greater versus lower risk score. We ran a paired t‐test to compare EM performance (total number of recalled words in three trials of 10‐word list) in co‐twins with greater versus lower risk score. Associations of individual factors with EM were studied with exact McNemar test.ResultMean difference in EM within twin pairs was 3.38 (SD = 2.50). Pairwise correlation of EM was r = 0.75 and seven twin pairs were discordant for EM. Co‐twins with lower risk score remembered more words (M = 13.25, SD = 5.59) than their co‐twins with greater risk score (M = 12.88, SD = 5.82), but this difference was not significant (p = 0.82). Examining each risk factor individually, the strongest – non‐significant – association was that co‐twins with greater life satisfaction had better EM in 5/6 pairs (p = 0.10).ConclusionPreliminary data did not indicate any significant within‐twin pair associations of dementia risk and episodic memory. As expected, co‐twins were highly similar in EM. Ongoing data collection will result in more twin pairs and greater statistical power to see if the suggestive association of greater life satisfaction (or other factors) with better EM is evident in nonagenarians.
BackgroundWe have established NONAGINTA – Memory and Health in 90‐year‐olds –study in a population‐based sample with 45 years of follow‐up. Our study is aimed to understand both, the antecedents of cognitive impairment and successful cognitive aging in the oldest‐old (90 years or older).MethodParticipants were nonagenarians from a population‐based longitudinal older Finnish Twin Cohort study with baseline questionnaire in 1975. Ongoing 90‐year‐old data collection included postal questionnaire and telephone administered cognitive testing. Episodic memory (EM) was measured with total words recalled in three trials of 10‐word list. Predictors of EM included cognitive, health‐related, and psychological factors. Self‐reported educational attainment, body mass index (BMI), physical activity (METhours/day), life satisfaction and neuroticism were measured in middle age (N = 55, age M = 46.2, SD = 1.7 years) and in old age (N = 59‐67, age M = 91.3, SD = 1.9 years). Semantic verbal fluency (number of animals in 1‐minute) and depressive symptoms (Center for Epidemiological Studies – Depression (CES‐D)) were measured only in old age. We used individual level linear regression models with age and sex as covariates and adjusted for family structure.ResultTo date, 67 individuals have cognitive data. On average, women (N = 36, M = 11.97, SD = 4.70) had better EM than men (N = 31, M = 11.10, SD = 4.74), but this difference was not statistically significant (p = 0.49). Better verbal fluency was significantly related to better EM (r = 0.34, p<0.001). Compared to those with 6 years of education, those with 7‐11 years and those with 12 or more years of education had significantly better EM: 4.03 (95%CI: 1.27‐6.80) (p = 0.005) and 5.75 (95%CI: 3.75‐7.45) (p<0.001) words more, respectively. Mean CES‐D was 12.3 (SD = 8.7) and 16% scored above the cut‐off for clinically significant depressive symptoms, however, depressive symptoms were not related to EM (p = 0.15). Middle age or old age BMI, physical activity, life satisfaction or neuroticism were not significantly related to EM (p’s >0.32).ConclusionOur preliminary results suggest that cognitive, but not midlife or old age physical or psychological health‐related factors, are associated with episodic memory performance in nonagenarians. Good episodic memory goes hand in hand with good semantic fluency and cognitive benefits of early life educational attainment are still evident in nonagenarians.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.