Race, polygenic risk and their association with incident dementia among older US adults

Socioeconomic area deprivation and its relationship with dementia, Parkinson's Disease and all-cause mortality among UK older adults: a multistate modeling approach

The study analyzed the association of area-level socioeconomic status (SES) with the risk of all-cause dementia, Parkinson's Disease (PD), and all-cause mortality using a multistate approach. Data from the UK Biobank were used (N = 363,663 50+y individuals, ≤15y follow-up), and Cox proportional hazards and multistate parametric models including Weibull regression were conducted, while cardiovascular health was tested as a potential mediator. In multistate models, socioeconomic area-level deprivation, measured by the Townsend Deprivation Index (TDI) z-score, was positively associated with the hazard of going from healthy into the 3 states of PD, dementia, and all-cause mortality (i.e. transitions 1: HR = 1.06, 95 % CI:1.02-1.10, P = 0.005, 2: HR = 1.19, 95 % CI: 1.16-1.22, P < 0.001 and 3: HR = 1.19, 95 % CI: 1.18-1.21, P < 0.001), with no association detected for transitions 4 (PD→Dementia), 5 (PD→Death), or 6 (Dementia→Death). Cardiovascular health did not mediate these associations. Socioeconomic area-level deprivation was directly associated with reduced survival rates from Healthy into Dementia, PD and Death.

How much can biomarkers explain sociodemographic inequalities in cognitive dysfunction and cognitive impairment? Results from a machine learning model in the Health and Retirement Study

BackgroundBiomarkers may be pathways by which social adversity affects cognitive aging and Alzheimer's disease and related dementias (ADRD) risk.ObjectiveHow much variance in cognitive dysfunction and cognitive impairment onset do blood-based and physiological biomarkers provide above and beyond easily attainable sociodemographic variables, and how much can biomarkers explain differences in cognitive functioning and ADRD by sociodemographic variables?MethodsWe utilize machine learning to generate measures of predicted cognitive dysfunction and cognitive impairment incidence based on 91 biomarkers, identify the relative importance of each biomarker, and examine how much these biomarkers mediate sociodemographic differences.ResultsMarkers related to cellular aging, neurodegeneration, diet and nutrition, immune functioning, and lung function were identified as important. Biomarkers mediated 47.2-77.3% of the variance associated with age, 22.7-35.2% of racial/ethnic differences in cognitive dysfunction, and 12.5-17.6% of educational differences.ConclusionsBiomarkers provide the potential to understand pathways linking sociodemographic characteristics to cognitive functioning and health. Future research should consider additional biomarkers and evaluate the specific systems that put people at risk for cognitive impairment.

Alzheimer's Disease polygenic risk, the plasma proteome, and dementia incidence among UK older adults

Alzheimer's Disease (AD) is a complex polygenic neurodegenerative disorder. Its genetic risk's relationship with all-cause dementia may be influenced by the plasma proteome. Up to 40,139 UK Biobank participants aged ≥ 50y at baseline assessment (2006-2010) were followed-up for ≤ 15 y for dementia incidence. Plasma proteomics were performed on a sub-sample of UK Biobank participants (k = 1,463 plasma proteins). AD polygenic risk scores (PRS) were used as the primary exposure and Cox proportional hazards models were conducted to examine the AD PRS-dementia relationship. A four-way decomposition model then partitioned the total effect (TE) of AD PRS on dementia into an effect due to mediation only, an effect due to interaction only, neither or both. The study found that AD PRS tertiles significantly increased the risk for all-cause dementia, particularly among women. The study specifically found that AD PRS was associated with a 79% higher risk for all-cause dementia for each unit increase (HR = 1.79, 95% CI: 1.70-1.87, P < 0.001). Eighty-six plasma proteins were significantly predicted by AD PRS, including a positive association with PLA2G7, BRK1, the glial acidic fibrillary protein (GFAP), neurofilament light chain (NfL), and negative with TREM2. Both GFAP and NfL significantly interacted synergistically with AD PRS to increase all-dementia risk (> 10% of TE is pure interaction), while GFAP was also an important consistent mediator in the AD PRS-dementia relationship. In summary, we detected significant interactions of NfL and GFAP with AD PRS, in relation to dementia incidence, suggesting potential for personalized dementia prevention and management.

Plasma proteomic biomarkers as mediators or moderators for the association between poor cardiovascular health and white matter microstructural integrity: The UK Biobank study

INTRODUCTION

The plasma proteome's mediating or moderating roles in the association between poor cardiovascular health (CVH) and brain white matter (WM) microstructural integrity are largely unknown.

METHODS

Data from 3953 UK Biobank participants were used (40-70 years, 2006-2010), with a neuroimaging visit between 2014 and 2021. Poor CVH was determined using Life's Essential 8 (LE8) and reversing standardized z-scores (LE8z _rev). The plasma proteome was examined as a potential mediator or moderator of LE8z _rev's effects on quantitative diffusion-weighted magnetic resonance imaging (dMRI) metrics.

RESULTS

LE8z_rev was significantly associated with deteriorated WM microstructural integrity, as reflected by lower tract-averaged fractional anisotropy (dMRI-FAmean), (β ± standared error (SE): -0.00152 ± 0.0003, p < 0.001) and higher tract-averaged orientation dispersion (dMRI-ODmean), (β ± SE:+0.00081 ± 0.00017, p < 0.001). Ten strongly mediating plasma proteins of 1463 were identified, with leptin as the principal driver.

DISCUSSION

Poor CVH is linked to poor WM microstructural integrity measures (lower FAmean and higher ODmean), mostly mediated through leptin.

HIGHLIGHTS

Up to 3953 UK Biobank participants were selected for this study. Poor cardiovascular health (CVH) was determined using Life's Essential 8. The plasma proteome was examined as a potential mediator or moderator of poor CVH's effect on dMRI metrics. Ten plasma proteins were identified with strong mediating effects, with leptin being the principal driver.

Poor sleep quality, dementia status and their association with all-cause mortality among older US adults

BACKGROUND

Evidence points to associations between sleep quality, dementia, and mortality. We examined whether poor sleep quality mediated or moderated the association between dementia and mortality risk among older US adults and vice versa, and whether these associations differed by sex and by race.

METHODS

The study investigated bi-directional associations between sleep quality, dementia and mortality in older US adults using data from the Health and Retirement Study (N = 6,991, mean age = 78.1y, follow-up: 2006-2020, number of deaths = 4,938). It tested interactions and mediating effects, using Cox proportional hazards models and four-way decomposition models.

RESULTS

Poor sleep quality was associated with increased mortality risk, particularly among male and White older adults. However, the association was reversed in the fully adjusted model, with a 7% decrease in risk per tertile. Probable dementia was associated with a two-fold increase in mortality risk, with a stronger association found among White adults. The association was markedly attenuated in the fully adjusted models. Sleep quality-stratified models showed a stronger positive association between dementia and mortality among individuals with better sleep quality. Both mediation and interaction were involved in explaining the total effects under study, though statistically significant total effects were mainly composed of controlled direct effects.

CONCLUSIONS

Poor sleep quality is directly related to mortality risk before lifestyle and health-related factors are adjusted. Dementia is linked to mortality risk, especially in individuals with better sleep quality, males, and White older adults. Future research should explore the underlying mechanisms.