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Genetic Associations Between Modifiable Risk Factors and Alzheimer Disease.
, , Luo, J, Thomassen, JQ, Bellenguez, C, Grenier-Boley, B, de Rojas, I, Castillo, A, Parveen, K, Küçükali, F, Nicolas, A, et al
JAMA network open. 2023;(5):e2313734
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Abstract
IMPORTANCE An estimated 40% of dementia is potentially preventable by modifying 12 risk factors throughout the life course. However, robust evidence for most of these risk factors is lacking. Effective interventions should target risk factors in the causal pathway to dementia. OBJECTIVE To comprehensively disentangle potentially causal aspects of modifiable risk factors for Alzheimer disease (AD) to inspire new drug targeting and improved prevention. DESIGN, SETTING, AND PARTICIPANTS This genetic association study was conducted using 2-sample univariable and multivariable mendelian randomization. Independent genetic variants associated with modifiable risk factors were selected as instrumental variables from genomic consortia. Outcome data for AD were obtained from the European Alzheimer & Dementia Biobank (EADB), generated on August 31, 2021. Main analyses were conducted using the EADB clinically diagnosed end point data. All analyses were performed between April 12 and October 27, 2022. EXPOSURES Genetically determined modifiable risk factors. MAIN OUTCOMES AND MEASURES Odds ratios (ORs) and 95% CIs for AD were calculated per 1-unit change of genetically determined risk factors. RESULTS The EADB-diagnosed cohort included 39 106 participants with clinically diagnosed AD and 401 577 control participants without AD. The mean age ranged from 72 to 83 years for participants with AD and 51 to 80 years for control participants. Among participants with AD, 54% to 75% were female, and among control participants, 48% to 60% were female. Genetically determined high-density lipoprotein (HDL) cholesterol concentrations were associated with increased odds of AD (OR per 1-SD increase, 1.10 [95% CI, 1.05-1.16]). Genetically determined high systolic blood pressure was associated with increased risk of AD after adjusting for diastolic blood pressure (OR per 10-mm Hg increase, 1.22 [95% CI, 1.02-1.46]). In a second analysis to minimize bias due to sample overlap, the entire UK Biobank was excluded from the EADB consortium; odds for AD were similar for HDL cholesterol (OR per 1-SD unit increase, 1.08 [95% CI, 1.02-1.15]) and systolic blood pressure after adjusting for diastolic blood pressure (OR per 10-mm Hg increase, 1.23 [95% CI, 1.01-1.50]). CONCLUSIONS AND RELEVANCE This genetic association study found novel genetic associations between high HDL cholesterol concentrations and high systolic blood pressure with higher risk of AD. These findings may inspire new drug targeting and improved prevention implementation.
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Sex differences in dementia risk and risk factors: Individual-participant data analysis using 21 cohorts across six continents from the COSMIC consortium.
Gong, J, Harris, K, Lipnicki, DM, Castro-Costa, E, Lima-Costa, MF, Diniz, BS, Xiao, S, Lipton, RB, Katz, MJ, Wang, C, et al
Alzheimer's & dementia : the journal of the Alzheimer's Association. 2023;(8):3365-3378
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Abstract
INTRODUCTION Sex differences in dementia risk, and risk factor (RF) associations with dementia, remain uncertain across diverse ethno-regional groups. METHODS A total of 29,850 participants (58% women) from 21 cohorts across six continents were included in an individual participant data meta-analysis. Sex-specific hazard ratios (HRs), and women-to-men ratio of hazard ratios (RHRs) for associations between RFs and all-cause dementia were derived from mixed-effect Cox models. RESULTS Incident dementia occurred in 2089 (66% women) participants over 4.6 years (median). Women had higher dementia risk (HR, 1.12 [1.02, 1.23]) than men, particularly in low- and lower-middle-income economies. Associations between longer education and former alcohol use with dementia risk (RHR, 1.01 [1.00, 1.03] per year, and 0.55 [0.38, 0.79], respectively) were stronger for men than women; otherwise, there were no discernible sex differences in other RFs. DISCUSSION Dementia risk was higher in women than men, with possible variations by country-level income settings, but most RFs appear to work similarly in women and men.
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Genetically downregulated Interleukin-6 signalling is associated with a lower risk of frailty.
Mourtzi, N, Georgakis, M, Ntanasi, E, Hatzimanolis, A, Ramirez, A, Heilmann-Heimbach, S, Grenier-Boley, B, Lambert, J, Yannakoulia, M, Kosmidis, M, et al
Age and ageing. 2023;(1)
Abstract
BACKGROUND numerous studies point towards a critical role of Interleukin 6 (IL-6) pathway in frailty pathogenesis yet the causal relationship between the two remains elusive. METHODS we selected genetic variants near the IL-6 receptor locus (IL-6R) associated with reduced C-reactive protein (CRP) levels, a downstream effector of IL-6 pathway, and we used them as genetic proxies of IL-6 signalling downregulation. We then performed a two-sample Mendelian randomisation (MR) to investigate the association with frailty status, as defined by the Frailty Index (FI) in 11,171 individuals from the Hellenic Longitudinal Investigation of Ageing and Diet (HELIAD) study. MR analysis was repeated after excluding depression or cognition-related FI items as well as following age or sex stratification. Association with frailty was also examined using an alternative instrument, weighted on s-IL-6R levels. Replication was attempted in UK Biobank dataset. RESULTS genetic predisposition to IL-6 signalling downregulation, weighted on CRP levels, was associated with lower risk of frailty, inserted either as categorical (odds ratio [95% confidence interval] = 0.15 [-3.39, -0.40], P = 0.013) or continuous variable (beta [se] = -0.09 [0.003], P = 0.0009). Sensitivity analyses revealed similar estimates across different MR methods with no evidence for horizontal pleiotropy or heterogeneity. Results remained robust after exclusion of depression or cognition-related FI items and following sex or age stratification. Genetically increased s-IL-6R levels were negatively correlated with frailty and this finding remained significant in a meta-analysis of UK Biobank and HELIAD cohorts. CONCLUSION our results support a potential causal effect of IL-6 signalling on frailty and further suggest that downregulation of IL-6 levels may reduce frailty risk.
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Mediterranean diet is associated with a lower probability of prodromal Parkinson's disease and risk for Parkinson's disease/dementia with Lewy bodies: A longitudinal study.
Maraki, MI, Yannakoulia, M, Xiromerisiou, G, Stefanis, L, Charisis, S, Giagkou, N, Kosmidis, MH, Dardiotis, E, Hadjigeorgiou, GM, Sakka, P, et al
European journal of neurology. 2023;(4):934-942
Abstract
BACKGROUND AND PURPOSE Lifestyle factors have been implicated in the long-lasting neurodegenerative process in prodromal Parkinson's disease (pPD). The aim was to investigate the associations between adherence to a Mediterranean diet (MeDi) and longitudinal changes of pPD probability and the development of Parkinson's disease (PD) or pPD in a Mediterranean older population. METHODS Data from the Hellenic Longitudinal Investigation of Aging and Diet cohort (community-dwelling individuals, aged ≥ 65 years) were used. A detailed food frequency questionnaire was used to evaluate dietary intake and calculate MeDi adherence score, ranging from 0 to 55, with higher scores indicating higher adherence. The probability of pPD was calculated according to the updated Movement Disorder Society research criteria. RESULTS In all, 1047 non-PD/dementia with Lewy bodies (DLB) participants were followed for 3 ± 1 years. MeDi adherence was associated with lower increase in pPD probability over time (b = -0.003, 95% confidence interval -0.006 to -0.001, p = 0.010). Forty-nine participants had incident possible/probable pPD (i.e., pPD probability ≥ 30%). Compared to the participants in the lowest quartile of MeDi adherence, those in the higher quartiles had an approximately 60%-70% lower risk for possible/probable pPD (p for trend 0.003). MeDi-pPD associations were driven by both motor and non-motor pPD markers and not from risk markers. Also, 21 participants were diagnosed with PD/DLB at follow-up. For each unit increase in the MeDi score, there was a 9%-10% lower risk for PD/DLB (hazard ratio 0.906 [95% confidence interval 0.823-0.997], p = 0.044). CONCLUSIONS Mediterranean diet adherence is associated with lower increase in pPD probability over time and lower possible/probable pPD and PD/DLB incidence in older Mediterranean people. More studies are needed to confirm our results in other populations.
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Dose-response relationship between late-life physical activity and incident dementia: A pooled analysis of 10 cohort studies of memory in an international consortium.
Wu, W, Ding, D, Zhao, Q, Xiao, Z, Luo, J, Ganguli, M, Hughes, TF, Jacobsen, E, Haan, MN, van Dang, K, et al
Alzheimer's & dementia : the journal of the Alzheimer's Association. 2023;(1):107-122
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INTRODUCTION Though consistent evidence suggests that physical activity may delay dementia onset, the duration and amount of activity required remains unclear. METHODS We harmonized longitudinal data of 11,988 participants from 10 cohorts in eight countries to examine the dose-response relationship between late-life physical activity and incident dementia among older adults. RESULTS Using no physical activity as a reference, dementia risk decreased with duration of physical activity up to 3.1 to 6.0 hours/week (hazard ratio [HR] 0.88, 95% confidence interval [CI] 0.67 to 1.15 for 0.1 to 3.0 hours/week; HR 0.68, 95% CI 0.52 to 0.89 for 3.1 to 6.0 hours/week), but plateaued with higher duration. For the amount of physical activity, a similar pattern of dose-response curve was observed, with an inflection point of 9.1 to 18.0 metabolic equivalent value (MET)-hours/week (HR 0.92, 95% CI 0.70 to 1.22 for 0.1 to 9.0 MET-hours/week; HR 0.70, 95% CI 0.53 to 0.93 for 9.1 to 18.0 MET-hours/week). DISCUSSION This cross-national analysis suggests that performing 3.1 to 6.0 hours of physical activity and expending 9.1 to 18.0/MET-hours of energy per week may reduce dementia risk.
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Author Correction: Common variants in Alzheimer's disease and risk stratification by polygenic risk scores.
de Rojas, I, Moreno-Grau, S, Tesi, N, Grenier-Boley, B, Andrade, V, Jansen, IE, Pedersen, NL, Stringa, N, Zettergren, A, Hernández, I, et al
Nature communications. 2023;(1):716
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Multi-nutrient interventions and cognitive ageing: are we barking up the right tree?
Young, HA, Geurts, L, Scarmeas, N, Benton, D, Brennan, L, Farrimond, J, Kiliaan, AJ, Pooler, A, Trovò, L, Sijben, J, et al
Nutrition research reviews. 2023;(2):471-483
Abstract
As we continue to elucidate the mechanisms underlying age-related brain diseases, the reductionist strategy in nutrition–brain function research has focused on establishing the impact of individual foods. However, the biological processes connecting diet and cognition are complex. Therefore, consideration of a combination of nutritional compounds may be most efficacious. One barrier to establishing the efficacy of multi-nutrient interventions is that the area lacks an established set of evidence-based guidelines for studying their effect on brain health. This review is an output of the International Life Sciences Institute (ILSI) Europe. A multi-disciplinary expert group was assembled with the aim of developing a set of considerations to guide research into the effects of multi-nutrient combinations on brain functions. Consensus recommendations converged on six key issues that should be considered to advance research in this area: (1) establish working mechanisms of the combination and contributions of each individual compound; (2) validate the relevance of the mechanisms for the targeted human condition; (3) include current nutrient status, intake or dietary pattern as inclusion/exclusion criteria in the study design; (4) select a participant population that is clinically and biologically appropriate for all nutritional components of the combination; (5) consider a range of cognitive outcomes; (6) consider the limits of reductionism and the ‘gold standard’ randomised controlled trial. These guiding principles will enhance our understanding of the interactive/complementary activities of dietary components, thereby strengthening the evidence base for recommendations aimed at delaying cognitive decline.
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Social connections and risk of incident mild cognitive impairment, dementia, and mortality in 13 longitudinal cohort studies of ageing.
Mahalingam, G, Samtani, S, Lam, BCP, Lipnicki, DM, Lima-Costa, MF, Blay, SL, Castro-Costa, E, Shifu, X, Guerchet, M, Preux, PM, et al
Alzheimer's & dementia : the journal of the Alzheimer's Association. 2023;(11):5114-5128
Abstract
INTRODUCTION Previous meta-analyses have linked social connections and mild cognitive impairment, dementia, and mortality. However, these used aggregate data from North America and Europe and examined a limited number of social connection markers. METHODS We used individual participant data (N = 39271, Mage = 70.67 (40-102), 58.86% female, Meducation = 8.43 years, Mfollow-up = 3.22 years) from 13 longitudinal ageing studies. A two-stage meta-analysis of Cox regression models examined the association between social connection markers with our primary outcomes. RESULTS We found associations between good social connections structure and quality and lower risk of incident mild cognitive impairment (MCI); between social structure and function and lower risk of incident dementia and mortality. Only in Asian cohorts, being married/in a relationship was associated with reduced risk of dementia, and having a confidante was associated with reduced risk of dementia and mortality. DISCUSSION Different aspects of social connections - structure, function, and quality - are associated with benefits for healthy aging internationally. HIGHLIGHTS Social connection structure (being married/in a relationship, weekly community group engagement, weekly family/friend interactions) and quality (never lonely) were associated with lower risk of incident MCI. Social connection structure (monthly/weekly friend/family interactions) and function (having a confidante) were associated with lower risk of incident dementia. Social connection structure (living with others, yearly/monthly/weekly community group engagement) and function (having a confidante) were associated with lower risk of mortality. Evidence from 13 longitudinal cohort studies of ageing indicates that social connections are important targets for reducing risk of incident MCI, incident dementia, and mortality. Only in Asian cohorts, being married/in a relationship was associated with reduced risk of dementia, and having a confidante was associated with reduced risk of dementia and mortality.
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Use of Antihypertensives, Blood Pressure, and Estimated Risk of Dementia in Late Life: An Individual Participant Data Meta-Analysis.
Lennon, MJ, Lam, BCP, Lipnicki, DM, Crawford, JD, Peters, R, Schutte, AE, Brodaty, H, Thalamuthu, A, Rydberg-Sterner, T, Najar, J, et al
JAMA network open. 2023;(9):e2333353
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IMPORTANCE The utility of antihypertensives and ideal blood pressure (BP) for dementia prevention in late life remains unclear and highly contested. OBJECTIVES To assess the associations of hypertension history, antihypertensive use, and baseline measured BP in late life (age >60 years) with dementia and the moderating factors of age, sex, and racial group. DATA SOURCE AND STUDY SELECTION Longitudinal, population-based studies of aging participating in the Cohort Studies of Memory in an International Consortium (COSMIC) group were included. Participants were individuals without dementia at baseline aged 60 to 110 years and were based in 15 different countries (US, Brazil, Australia, China, Korea, Singapore, Central African Republic, Republic of Congo, Nigeria, Germany, Spain, Italy, France, Sweden, and Greece). DATA EXTRACTION AND SYNTHESIS Participants were grouped in 3 categories based on previous diagnosis of hypertension and baseline antihypertensive use: healthy controls, treated hypertension, and untreated hypertension. Baseline systolic BP (SBP) and diastolic BP (DBP) were treated as continuous variables. Reporting followed the Preferred Reporting Items for Systematic Review and Meta-Analyses of Individual Participant Data reporting guidelines. MAIN OUTCOMES AND MEASURES The key outcome was all-cause dementia. Mixed-effects Cox proportional hazards models were used to assess the associations between the exposures and the key outcome variable. The association between dementia and baseline BP was modeled using nonlinear natural splines. The main analysis was a partially adjusted Cox proportional hazards model controlling for age, age squared, sex, education, racial group, and a random effect for study. Sensitivity analyses included a fully adjusted analysis, a restricted analysis of those individuals with more than 5 years of follow-up data, and models examining the moderating factors of age, sex, and racial group. RESULTS The analysis included 17 studies with 34 519 community dwelling older adults (20 160 [58.4%] female) with a mean (SD) age of 72.5 (7.5) years and a mean (SD) follow-up of 4.3 (4.3) years. In the main, partially adjusted analysis including 14 studies, individuals with untreated hypertension had a 42% increased risk of dementia compared with healthy controls (hazard ratio [HR], 1.42; 95% CI 1.15-1.76; P = .001) and 26% increased risk compared with individuals with treated hypertension (HR, 1.26; 95% CI, 1.03-1.53; P = .02). Individuals with treated hypertension had no significant increased dementia risk compared with healthy controls (HR, 1.13; 95% CI, 0.99-1.28; P = .07). The association of antihypertensive use or hypertension status with dementia did not vary with baseline BP. There was no significant association of baseline SBP or DBP with dementia risk in any of the analyses. There were no significant interactions with age, sex, or racial group for any of the analyses. CONCLUSIONS AND RELEVANCE This individual patient data meta-analysis of longitudinal cohort studies found that antihypertensive use was associated with decreased dementia risk compared with individuals with untreated hypertension through all ages in late life. Individuals with treated hypertension had no increased risk of dementia compared with healthy controls.
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Nutritional metabolism and cerebral bioenergetics in Alzheimer's disease and related dementias.
Yassine, HN, Self, W, Kerman, BE, Santoni, G, Navalpur Shanmugam, N, Abdullah, L, Golden, LR, Fonteh, AN, Harrington, MG, Gräff, J, et al
Alzheimer's & dementia : the journal of the Alzheimer's Association. 2022
Abstract
Disturbances in the brain's capacity to meet its energy demand increase the risk of synaptic loss, neurodegeneration, and cognitive decline. Nutritional and metabolic interventions that target metabolic pathways combined with diagnostics to identify deficits in cerebral bioenergetics may therefore offer novel therapeutic potential for Alzheimer's disease (AD) prevention and management. Many diet-derived natural bioactive components can govern cellular energy metabolism but their effects on brain aging are not clear. This review examines how nutritional metabolism can regulate brain bioenergetics and mitigate AD risk. We focus on leading mechanisms of cerebral bioenergetic breakdown in the aging brain at the cellular level, as well as the putative causes and consequences of disturbed bioenergetics, particularly at the blood-brain barrier with implications for nutrient brain delivery and nutritional interventions. Novel therapeutic nutrition approaches including diet patterns are provided, integrating studies of the gut microbiome, neuroimaging, and other biomarkers to guide future personalized nutritional interventions.