Improving risk indexes for Alzheimer's disease and related dementias for use in midlife

Risk factors for Alzheimer's disease and cognitive function before middle age in a U.S. representative population-based study

Background

Alzheimer's disease is a major health concern in the U.S., but most research has focused on older populations. We examined whether established risk factors and blood biomarkers are associated with cognition before midlife.

Methods

Data from the National Longitudinal Study of Adolescent to Adult Health (Add Health) were analyzed. Participants were enrolled in 1994-95 (grades 7-12) and followed through 2018. We cross-sectionally analyzed weighted survey and biomarker data from Waves IV and V. We measured the Cardiovascular Risk Factors, Aging, and Incidence of Dementia (CAIDE) score comprised of age, education, sex, systolic blood pressure, body mass index, cholesteroal, and physical activity and apolipoprotein E ε4 allele (APOE ε4) status. We also measured total Tau and Neurofilament light (NfL), high sensitivity C-reactive protein (hsCRP), Interleukin (IL)-1β, IL-6, IL-8, IL-10, and Tumor necrosis factor alpha (TNF-α). Outcomes included immediate word recall, delayed word recall, and backward digit span.

Findings

Analytic sample sizes ranged from 4507 to 11,449 participants in Wave IV and from 529 to 1121 participants in Wave V. The survey-weighted median (IQR) age was 28 (26-29) years in Wave IV and 38 (36-29) years in Wave V. About half of the survey-weighted Wave IV participants were female (48.4-52.1% across analytic samples), 71.4-72.5% were White, 12.5-14.9% were Black, and 9.3-10.2% were Hispanic. In Wave V, 43.6-46.8% were female, 68.7-69.3% were White, 17.1%-20.0% were Black, and 7.3%-9.6% were Hispanic. The CAIDE score was associated with all cognition measures in Wave IV. For example, among adults aged 24-34, each 1-point increase in CAIDE was associated with a 0.03 standard deviation lower backward digit span score (95% CI: -0.04, -0.02). Total Tau was associated with immediate word recall in Wave V (β = -0.13, 95% CI: -0.23, -0.04). Wave IV hsCRP and IL-10 and Wave V IL-6, IL-1β, and IL-8 were also associated with lower cognitive scores.

Interpretation

Key risk factors for Alzheimer's Disease are linked to cognitive function as early as ages 24-44, highlighting the need for early prevention in the US.

Funding

NIHP01HD31921, U01AG071448, U01AG071450, R01AG057800, P30AG066615, T32HD091058, P2CHD050924.

Linkages between incarceration and health for older adults

The aging population in United States (US) correctional facilities has grown dramatically over the last several decades. At present, roughly one in four adults incarcerated in US prisons are at least 50 years of age. Research over the last ten years has likewise expanded to catalog the impacts of incarceration on older adults, and the myriad ways incarceration is unique for this population. In this paper, we summarize the state of the literature at the intersection of incarceration, health, and aging. We begin by outlining the impacts of incarceration on a range of individual health outcomes for older adults. Next, we offer targeted policy implications to address the health consequences of incarceration for older adults. Finally, we conclude by offering a research agenda that emphasizes theory building, jail-based approaches, and expansion of what is known about older women, cognitive impairment, correctional staff perspectives, and interventions to enhance the health of older persons who are incarcerated.

Examining the relationship between plasma pTau181 and cognitive decline, structural brain integrity, and biological ageing in midlife

INTRODUCTION

Although plasma pTau181 has been shown to accurately discriminate patients with Alzheimer's disease from healthy older adults, its utility as a preclinical biomarker in middle-aged community-based cohorts is unclear.

METHODS

Participants were members of the Dunedin Multidisciplinary Health and Development Study, a longitudinal study of 1037 people born in New Zealand in 1972-1973. Plasma pTau181, MRI-based brain structure, and DunedinPACE (an epigenetic biomarker of biological ageing) were measured at age 45; cognition was measured in childhood and age 45.

RESULTS

We observed a wide range of pTau181 concentrations in our same-aged sample (n=856; M=13.6pg/mL, SD=9.1pg/mL). Males had significantly higher pTau181 concentrations than females. No statistically significant associations were observed with cognitive decline, lower structural brain integrity, or accelerated biological ageing.

DISCUSSION

In this midlife cohort, wide variation in pTau181 concentrations was present by age 45, but was not associated with patterns of AD-risk in cognition, brain structure, or biological ageing.

Measures of retinal health successfully capture risk for Alzheimer's disease and related dementias at midlife

BACKGROUND

Identification of at-risk individuals who would benefit from early intervention for Alzheimer's disease and related dementias (ADRD) is critical as new treatments are developed. Measures of retinal health could offer accessible and low-cost indication of pre-morbid disease risk, but their association with ADRD risk is unknown.

OBJECTIVE

To determine whether midlife retinal neuronal and microvascular measures are associated with ADRD risk-index scores and individual domains of ADRD risk.

METHODS

Data were from the Dunedin Multidisciplinary Health and Development Study, a population-representative longitudinal New Zealand-based birth cohort study. 94.1% (N = 938) of living Study members were seen at age 45 (2017-2019). Retinal neuronal (retinal nerve fiber layer (RNFL) and ganglion cell-inner plexiform layer (GC-IPL)) and microvascular (arterioles and venules) measures were used as predictors. Outcome measures were four top ADRD risk indexes (CAIDE, LIBRA, Lancet, and ADU-ADRI), and a comprehensive midlife ADRD risk index, the DunedinARB.

RESULTS

Poorer retinal microvascular health (narrower arterioles and wider venules) was associated with greater ADRD risk (βs = 0.16-0.31; ps < 0.001). Thinner RNFL was modestly associated with higher ADRD risk (βs = 0.05-0.08; ps = 0.02-0.13). Follow-up tests of distinct domains of ADRD risk indicated that while RNFL associations reflected cardiometabolic risk only, microvascular measures were associated with diverse ADRD risk factors.

CONCLUSIONS

Measures of retinal health, particularly microvascular measures, successfully capture ADRD risk across several domains of known risk factors, even at the young midlife age of 45 years. Retinal microvascular imaging may be an accessible, scalable, and relatively low-cost method of assessing ADRD risk among middle-aged adults.

Potential for reducing dementia risk: association of the CAIDE score with additional lifestyle components from the LIBRA score in a population at high risk of dementia

OBJECTIVES

Various dementia risk scores exist that assess different factors. We investigated the association between the Cardiovascular Risk Factors, Aging, and Incidence of Dementia (CAIDE) score and modifiable risk factors in the Lifestyle for Brain Health (LIBRA) score in a German population at high risk of Alzheimer's disease.

METHOD

Baseline data of 807 participants of AgeWell.de (mean age: 68.8 years (SD = 4.9)) were analysed. Stepwise multivariable regression was used to examine the association between the CAIDE score and additional risk factors of the LIBRA score. Additionally, we examined the association between dementia risk models and cognitive performance, as measured by the Montreal Cognitive Assessment.

RESULTS

High cognitive activity (β = -0.016, p < 0.001) and high fruit and vegetable intake (β = -0.032, p < 0.001) correlated with lower CAIDE scores, while diabetes was associated with higher CAIDE scores (β = 0.191; p = 0.032). Although all were classified as high risk on CAIDE, 31.5% scored ≤0 points on LIBRA, indicating a lower risk of dementia. Higher CAIDE and LIBRA scores were associated with lower cognitive performance.

CONCLUSION

Regular cognitive activities and increased fruit and vegetable intake were associated with lower CAIDE scores. Different participants are classified as being at-risk based on the dementia risk score used.

Cardiovascular risk factors among older persons with cognitive frailty in middle income country

BACKGROUND

Cognitive frailty, characterized by the coexistence of cognitive impairment and physical frailty, represents a multifaceted challenge in the aging population. The role of cardiovascular risk factors in this complex interplay is not yet fully understood.

AIM

To investigate the relationships between cardiovascular risk factors and older persons with cognitive frailty by pooling data from two cohorts of studies in Malaysia.

METHODS

A comprehensive approach was employed, with a total of 512 community-dwelling older persons aged 60 years and above, involving two cohorts of older persons from previous studies. Datasets related to cardiovascular risks, namely sociodemographic factors, and cardiovascular risk factors, including hypertension, diabetes, hypercholesterolemia, anthropometric characteristics and biochemical profiles, were pooled for analysis. Cognitive frailty was defined based on the Clinical Dementia Rating scale and Fried frailty score. Cardiovascular risk was determined using Framingham risk score. Statistical analyses were conducted using SPSS version 21.

RESULTS

Of the study participants, 46.3% exhibited cognitive frailty. Cardiovascular risk factors including hypertension (OR:1.60; 95%CI: 1.12-2.30), low fat-free mass (OR:0.96; 95%CI: 0.94-0.98), high percentage body fat (OR:1.04; 95%CI: 1.02-1.06), high waist circumference (OR:1.02; 95%CI: 1.01-1.04), high fasting blood glucose (OR:1.64; 95%CI: 1.11-2.43), high Framingham risk score (OR:1.65; 95%CI: 1.17-2.31), together with sociodemographic factors, i.e., being single (OR 3.38; 95%CI: 2.26-5.05) and low household income (OR 2.18; 95%CI: 1.44-3.30) were found to be associated with cognitive frailty.

CONCLUSION

Cardiovascular-risk specific risk factors and sociodemographic factors were associated with risk of cognitive frailty, a prodromal stage of dementia. Early identification and management of cardiovascular risk factors, particularly among specific group of the population might mitigate the risk of cognitive frailty, hence preventing dementia.

Brain structure and connectivity mediate the association between lifestyle and cognition: The Maastricht Study

Life-course exposure to risk and protective factors impacts brain macro- and micro-structure, which in turn affects cognition. The concept of brain-age gap assesses brain health by comparing an individual's neuroimaging-based predicted age with their calendar age. A higher BAG implies accelerated brain ageing and is expected to be associated with worse cognition. In this study, we comprehensively modelled mutual associations between brain health and lifestyle factors, brain age and cognition in a large, middle-aged population. For this study, cognitive test scores, lifestyle and 3T MRI data for n = 4881 participants [mean age (± SD) = 59.2 (±8.6), 50.1% male] were available from The Maastricht Study, a population-based cohort study with extensive phenotyping. Whole-brain volumes (grey matter, cerebrospinal fluid and white matter hyperintensity), cerebral microbleeds and structural white matter connectivity were calculated. Lifestyle factors were combined into an adapted LIfestyle for BRAin health weighted sum score, with higher score indicating greater dementia risk. Cognition was calculated by averaging z-scores across three cognitive domains (memory, information processing speed and executive function and attention). Brain-age gap was calculated by comparing calendar age to predictions from a neuroimaging-based multivariable regression model. Paths between LIfestyle for BRAin health tertiles, brain-age gap and cognitive function were tested using linear regression and structural equation modelling, adjusting for sociodemographic and clinical confounders. The results show that cerebrospinal fluid, grey matter, white matter hyperintensity and cerebral microbleeds best predicted brain-age gap (R 2 = 0.455, root mean squared error = 6.44). In regression analysis, higher LIfestyle for BRAin health scores (greater dementia risk) were associated with higher brain-age gap (standardized regression coefficient β = 0.126, P < 0.001) and worse cognition (β = -0.046, P = 0.013), while higher brain-age gap was associated with worse cognition (β=-0.163, P < 0.001). In mediation analysis, 24.7% of the total difference in cognition between the highest and lowest LIfestyle for BRAin health tertile was mediated by brain-age gap (β indirect = -0.049, P < 0.001; β total = -0.198, P < 0.001) and an additional 3.8% was mediated via connectivity (β indirect = -0.006, P < 0.001; β total = -0.150, P < 0.001). Findings suggest that associations between health- and lifestyle-based risk/protective factors (LIfestyle for BRAin health) and cognition can be partially explained by structural brain health markers (brain-age gap) and white matter connectivity markers. Lifestyle interventions targeted at high-risk individuals in mid-to-late life may be effective in promoting and preserving cognitive function in the general public.

Dementia, dementia's risk factors and premorbid brain structure are concentrated in disadvantaged areas: National register and birth-cohort geographic analyses

INTRODUCTION

Dementia risk may be elevated in socioeconomically disadvantaged neighborhoods. Reasons for this remain unclear, and this elevation has yet to be shown at a national population level.

METHODS

We tested whether dementia was more prevalent in disadvantaged neighborhoods across the New Zealand population (N = 1.41 million analytic sample) over a 20-year observation. We then tested whether premorbid dementia risk factors and MRI-measured brain-structure antecedents were more prevalent among midlife residents of disadvantaged neighborhoods in a population-representative NZ-birth-cohort (N = 938 analytic sample).

RESULTS

People residing in disadvantaged neighborhoods were at greater risk of dementia (HR per-quintile-disadvantage-increase = 1.09, 95% confidence interval [CI]:1.08-1.10) and, decades before clinical endpoints typically emerge, evidenced elevated dementia-risk scores (CAIDE, LIBRA, Lancet, ANU-ADRI, DunedinARB; β's 0.31-0.39) and displayed dementia-associated brain structural deficits and cognitive difficulties/decline.

DISCUSSION

Disadvantaged neighborhoods have more residents with dementia, and decades before dementia is diagnosed, residents have more dementia-risk factors and brain-structure antecedents. Whether or not neighborhoods causally influence risk, they may offer scalable opportunities for primary dementia prevention.

Social isolation from childhood to mid-adulthood: is there an association with older brain age?

BACKGROUND

Older brain age - as estimated from structural MRI data - is known to be associated with detrimental mental and physical health outcomes in older adults. Social isolation, which has similar detrimental effects on health, may be associated with accelerated brain aging though little is known about how different trajectories of social isolation across the life course moderate this association. We examined the associations between social isolation trajectories from age 5 to age 38 and brain age assessed at age 45.

METHODS

We previously created a typology of social isolation based on onset during the life course and persistence into adulthood, using group-based trajectory analysis of longitudinal data from a New Zealand birth cohort. The typology comprises four groups: 'never-isolated', 'adult-only', 'child-only', and persistent 'child-adult' isolation. A brain age gap estimate (brainAGE) - the difference between predicted age from structural MRI date and chronological age - was derived at age 45. We undertook analyses of brainAGE with trajectory group as the predictor, adjusting for sex, family socio-economic status, and a range of familial and child-behavioral factors.

RESULTS

Older brain age in mid-adulthood was associated with trajectories of social isolation after adjustment for family and child confounders, particularly for the 'adult-only' group compared to the 'never-isolated' group.

CONCLUSIONS

Although our findings are associational, they indicate that preventing social isolation, particularly in mid-adulthood, may help to avert accelerated brain aging associated with negative health outcomes later in life.