| 1. |
- Ericsson, Malin, et al.
(författare)
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Educational Influences on Late-Life Health : Genetic Propensity and Attained Education
- 2024
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Ingår i: The journals of gerontology. Series B, Psychological sciences and social sciences. - 1079-5014 .- 1758-5368. ; 79:1
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: The educational gradient in late-life health is well established. Despite this, there are still ambiguities concerning the role of underlying confounding by genetic influences and gene-environment (GE) interplay. Here, we investigate the role of educational factors (attained and genetic propensities) on health and mortality in late life using genetic propensity for educational attainment (as measured by a genome-wide polygenic score, PGSEdu) and attained education.Methods: By utilizing genetically informative twin data from the Swedish Twin Registry (n = 14,570), we investigated influences of the educational measures, familial confounding as well as the possible presence of passive GE correlation on both objective and subjective indicators of late-life health, that is, the Frailty Index, Multimorbidity, Self-rated health, cardiovascular disease, and all-cause mortality.Results: Using between-within models to adjust for shared familial factors, we found that the relationship between educational level and health and mortality later in life persisted despite controlling for familial confounding. PGSEdu and attained education both uniquely predicted late-life health and mortality, even when mutually adjusted. Between-within models of PGSEdu on the health outcomes in dizygotic twins showed weak evidence for passive GE correlation (prGE) in the education-health relationship.Discussion: Both genetic propensity to education and attained education are (partly) independently associated with health in late life. These results lend further support for a causal education-health relationship but also raise the importance of genetic contributions and GE interplay.
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| 2. |
- Gatz, Margaret, et al.
(författare)
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Dementia : Genes, environments, interactions
- 2014
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Ingår i: Behavior genetics of cognition across the lifespan. - New York : Springer. - 9781461474470 - 9781461474463 ; , s. 201-231
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Bokkapitel (refereegranskat)abstract
- Dementia is an increasingly prevalent disorder as the world population ages, with Alzheimer disease the most common cause. Twin studies find concordance to be substantially higher among monozygotic as compared with dizygotic twin pairs. While a few genes have been identified that are responsible for early-onset Alzheimer disease, they account for well under 5 % of all cases. Among susceptibility genes for Alzheimer disease identified by association studies, population attributable fraction for the most prominent of these—apolipoprotein E—is estimated to be about 25 %, whereas other genes at best predict another 20 %. There are few strong environmental risk or protective factors, with vascular risks the best established, although with mechanisms still not fully understood. It seems likely that clusters of risk alleles, interactions between risk alleles and environmental exposures, and epigenetic mechanisms play a role in explaining Alzheimer disease, with different combinations of influences culminating in the observed pathophysiology. In particular, environmental exposures early in life could lead to deleterious changes in gene expression in late life.
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| 3. |
- Karlsson, Ida K., et al.
(författare)
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Adiposity and the risk of dementia : mediating effects from inflammation and lipid levels
- 2022
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Ingår i: European Journal of Epidemiology. - : Springer Nature Switzerland AG.. - 0393-2990 .- 1573-7284. ; 37:12, s. 1261-1271
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Tidskriftsartikel (refereegranskat)abstract
- While midlife adiposity is a risk factor for dementia, adiposity in late-life appears to be associated with lower risk. What drives the associations is poorly understood, especially the inverse association in late-life. Using results from genome-wide association studies, we identified inflammation and lipid metabolism as biological pathways involved in both adiposity and dementia. To test if these factors mediate the effect of midlife and/or late-life adiposity on dementia, we then used cohort data from the Swedish Twin Registry, with measures of adiposity and potential mediators taken in midlife (age 40–64, n = 5999) or late-life (age 65–90, n = 7257). Associations between body-mass index (BMI), waist-hip ratio (WHR), C-reactive protein (CRP), lipid levels, and dementia were tested in survival and mediation analyses. Age was used as the underlying time scale, and sex and education included as covariates in all models. Fasting status was included as a covariate in models of lipids. One standard deviation (SD) higher WHR in midlife was associated with 25% (95% CI 2–52%) higher dementia risk, with slight attenuation when adjusting for BMI. No evidence of mediation through CRP or lipid levels was present. After age 65, one SD higher BMI, but not WHR, was associated with 8% (95% CI 1–14%) lower dementia risk. The association was partly mediated by higher CRP, and suppressed when high-density lipoprotein levels were low. In conclusion, the negative effects of midlife adiposity on dementia risk were driven directly by factors associated with body fat distribution, with no evidence of mediation through inflammation or lipid levels. There was an inverse association between late-life adiposity and dementia risk, especially where the body’s inflammatory response and lipid homeostasis is intact.
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| 4. |
- Karlsson, Ida K., et al.
(författare)
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Age-dependent effects of body mass index across the adult life span on the risk of dementia : A cohort study with a genetic approach
- 2020
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Ingår i: BMC Medicine. - : BioMed Central. - 1741-7015. ; 18:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: While a high body mass index (BMI) in midlife is associated with higher risk of dementia, high BMI in late-life may be associated with lower risk. This study combined genetic designs with longitudinal data to achieve a better understanding of this paradox. Methods: We used longitudinal data from 22,156 individuals in the Swedish Twin Registry (STR) and 25,698 from the Health and Retirement Study (HRS). The STR sample had information about BMI from early adulthood through late-life, and the HRS sample from age 50 through late-life. Survival analysis was applied to investigate age-specific associations between BMI and dementia risk. To examine if the associations are influenced by genetic susceptibility to higher BMI, an interaction between BMI and a polygenic score for BMI (PGSBMI) was included in the models and results stratified into those with genetic predisposition to low, medium, and higher BMI. In the STR, co-twin control models were applied to adjust for familial factors beyond those captured by the PGSBMI. Results: At age 35-49, 5 units higher BMI was associated with 15% (95% CI 7-24%) higher risk of dementia in the STR. There was a significant interaction (p = 0.04) between BMI and the PGSBMI, and the association present only among those with genetic predisposition to low BMI (HR 1.38, 95% CI 1.08-1.78). Co-twin control analyses indicated genetic influences. After age 80, 5 units higher BMI was associated with 10-11% lower risk of dementia in both samples. There was a significant interaction between late-life BMI and the PGSBMI in the STR (p = 0.01), but not the HRS, with the inverse association present only among those with a high PGSBMI (HR 0.70, 95% CI 0.52-0.94). No genetic influences were evident from co-twin control models of late-life BMI. Conclusions: Not only does the association between BMI and dementia differ depending on age at BMI measurement, but also the effect of genetic influences. In STR, the associations were only present among those with a BMI in opposite direction of their genetic predisposition, indicating that the association between BMI and dementia across the life course might be driven by environmental factors and hence likely modifiable. © 2020 The Author(s).
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| 5. |
- Karlsson, Ida K., et al.
(författare)
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Apolipoprotein E DNA methylation and late-life disease
- 2018
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Ingår i: International Journal of Epidemiology. - : Oxford University Press. - 0300-5771 .- 1464-3685. ; 47:3, s. 899-907
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Tidskriftsartikel (refereegranskat)abstract
- Background: This study aims to investigate if DNA methylation of the apolipoprotein E (APOE) locus affects the risks of dementia, Alzheimers disease (AD) or cardiovascular disease (CVD).Methods: DNA methylation across the APOE gene has previously been categorized into three distinct regions: a hypermethylated region in the promoter, a hypomethylated region in the first two introns and exons and a hypermethylated region in the 3'exon that also harbours the APOE epsilon 2 and epsilon 4 alleles. DNA methylation levels in leukocytes were measured using the Illumina 450K array in 447 Swedish twins (mean age 78.1 years). We used logistic regression to investigate whether methylation levels in those regions affect the odds of disease.Results: We found that methylation levels in the promoter region were associated with dementia and AD after adjusting for sex, age at blood draw, education, smoking and relatedness among twins [odds ratio (OR) 1.32 per standard deviation increase in methylation levels, 95% confidence interval (CI) 1.08-1.62 for dementia; OR 1.38, 95% CI 1.07-1.78 for AD). We did not detect any difference in methylation levels between CVD cases and controls. Results were similar when comparing within discordant twin pairs, and did not differ as a function of APOE genotype.Conclusions: We found that higher DNA methylation levels in the promoter region of APOE increase the odds of dementia and AD, but not CVD. The effect was independent of APOE genotype, indicating that allelic variation and methylation variation in APOE may act independently to increase the risk of dementia.
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| 6. |
- Karlsson, Ida K., et al.
(författare)
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Change in cognition and body mass index in relation to preclinical dementia
- 2021
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Ingår i: Alzheimer’s & Dementia. - : John Wiley & Sons. - 2352-8737. ; 7:1
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: To study if declining cognition drives weight loss in preclinical dementia, we examined the longitudinal association between body mass index (BMI) and cognitive abilities in individuals who did or did not later develop dementia.Methods: Using data from individuals spanning age 50 to 89, we applied dual change score models separately in individuals who remained cognitively intact (n = 1498) and those who were diagnosed with dementia within 5 years of last assessment (n = 459).Results: Among the cognitively intact, there was a bidirectional association: Stable BMI predicted stable cognition and vice versa. Among individuals who were subsequently diagnosed with dementia, the association was unidirectional: Higher BMI predicted declining cognition but cognition did not predict change in BMI.Discussion: Although BMI and cognition stabilized each other when cognitive functioning was intact, this buffering effect was missing in the preclinical dementia phase. This finding indicates that weight loss in preclinical dementia is not driven by declining cognition.
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| 7. |
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| 8. |
- Karlsson, Ida K., et al.
(författare)
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Measuring heritable contributions to Alzheimer's disease : polygenic risk score analysis with twins
- 2022
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Ingår i: Brain Communications. - : Oxford University Press. - 2632-1297. ; 4:1
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Tidskriftsartikel (refereegranskat)abstract
- The heritability of Alzheimer's disease estimated from twin studies is greater than the heritability derived from genome-based studies, for reasons that remain unclear. We apply both approaches to the same twin sample, considering both Alzheimer's disease polygenic risk scores and heritability from twin models, to provide insight into the role of measured genetic variants and to quantify uncaptured genetic risk. A population-based heritability and polygenic association study of Alzheimer's disease was conducted between 1986 and 2016 and is the first study to incorporate polygenic risk scores into biometrical twin models of Alzheimer's disease. The sample included 1586 twins drawn from the Swedish Twin Registry which were nested within 1137 twin pairs (449 complete pairs and 688 incomplete pairs) with clinically based diagnoses and registry follow-up (M-age = 85.28, SD = 7.02; 44% male; 431 cases and 1155 controls). We report contributions of polygenic risk scores at P < 1 x 10(-5), considering a full polygenic risk score (PRS), PRS without the APOE region (PRS.no.APOE) and PRS.no.APOE plus directly measured APOE alleles. Biometric twin models estimated the contribution of environmental influences and measured (PRS) and unmeasured genes to Alzheimer's disease risk. The full PRS and PRS.no.APOE contributed 10.1 and 2.4% to Alzheimer's disease risk, respectively. When APOE e4 alleles were added to the model with the PRS.no.APOE, the total contribution was 11.4% to Alzheimer's disease risk, where APOE e4 explained 9.3% and PRS.no.APOE dropped from 2.4 to 2.1%. The total genetic contribution to Alzheimer's disease risk, measured and unmeasured, was 71% while environmental influences unique to each twin accounted for 29% of the risk. The APOE region accounts for much of the measurable genetic contribution to Alzheimer's disease, with a smaller contribution from other measured polygenic influences. Importantly, substantial background genetic influences remain to be understood. Karlsson et al. report that measured polygenic scores from genome-based studies, including an outsized role for APOE, explain only a fraction of the heritability indicated by twin models of Alzheimer's disease, leaving most genetic risk for Alzheimer's disease unexplained. Sensitive designs are needed to capture all the genetic influences.
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| 9. |
- Karlsson, Ida K., et al.
(författare)
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The dynamic association between body mass index and cognition from midlife through late-life, and the effect of sex and genetic influences
- 2021
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Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Body mass index (BMI) is associated with cognitive abilities, but the nature of the relationship remains largely unexplored. We aimed to investigate the bidirectional relationship from midlife through late-life, while considering sex differences and genetic predisposition to higher BMI. We used data from 23,892 individuals of European ancestry from the Health and Retirement Study, with longitudinal data on BMI and three established cognitive indices: mental status, episodic memory, and their sum, called total cognition. To investigate the dynamic relationship between BMI and cognitive abilities, we applied dual change score models of change from age 50 through 89, with a breakpoint at age 65 or 70. Models were further stratified by sex and genetic predisposition to higher BMI using tertiles of a polygenic score for BMI (PGSBMI). We demonstrated bidirectional effects between BMI and all three cognitive indices, with higher BMI contributing to steeper decline in cognitive abilities in both midlife and late-life, and higher cognitive abilities contributing to less decline in BMI in late-life. The effects of BMI on change in cognitive abilities were more evident in men compared to women, and among those in the lowest tertile of the PGSBMI compared to those in the highest tertile, while the effects of cognition on BMI were similar across groups. In conclusion, these findings highlight a reciprocal relationship between BMI and cognitive abilities, indicating that the negative effects of a higher BMI persist from midlife through late-life, and that weight-loss in late-life may be driven by cognitive decline.
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