The Relationship of APOE ε4, Race, and Sex on the Age of Onset and Risk of Dementia

Neuropsychiatric Comorbidities and Psychotropic Medication Use in Medicare Beneficiaries With Dementia by Sex and Race

BACKGROUND

Neuropsychiatric symptoms affect the majority of dementia patients. Past studies report high rates of potentially inappropriate prescribing of psychotropic medications in this population. We investigate differences in neuropsychiatric diagnoses and psychotropic medication prescribing in a local US cohort by sex and race.

METHODS

We utilize Medicare claims and prescription fill records in a cohort of 100% Medicare North and South Carolina beneficiaries ages 50 and above for the year 2017 with a dementia diagnosis. We identify dementia and quantify diagnosis of anxiety, depression and psychosis using validated coding algorithms. We search Medicare claims for antianxiety, antidepressant and antipsychotic medications to determine prescriptions filled.

RESULTS

Anxiety and depression were diagnosed at higher rates in White patients; psychosis at higher rates in Black patients. (P < .001) Females were diagnosed with anxiety, depression and psychosis at higher rates than males (P < .001) and filled more antianxiety and antidepressant medications than males. (P < .001) Black and Other race patients filled more antipsychotic medications for anxiety, depression and psychosis than White patients. (P < .001) Antidepressants were prescribed at higher rates than antianxiety or antipsychotic medications across all patients and diagnoses. Of patients with no neuropsychiatric diagnosis, 11.4% were prescribed an antianxiety medication, 22.8% prescribed an antidepressant and 7.6% prescribed an antipsychotic.

CONCLUSIONS

The high fill rate of antianxiety (benzodiazepine) medications in dementia patients, especially females is a concern. Patients are prescribed psychotropic medications at high rates. This practice may represent potentially inappropriate prescribing. Patient/caregiver education with innovative community outreach and care delivery models may help decrease medication use.

The importance of education for understanding variability of dementia onset in the United States

BACKGROUND

Greater levels of education are associated with lower risk of dementia, but less is known about how education is also associated with the compression of dementia incidence.

OBJECTIVE

We extend the literature on morbidity compression by evaluating whether increased levels of education are associated with greater dementia compression. We evaluate these patterns across race and gender groups.

METHODS

We use the Health and Retirement Study (2000-2016), a nationally representative longitudinal study of older adults in the United States. To evaluate the onset and compression of dementia across education groups, we examine the age-specific distribution of dementia events, identifying the modal age of onset and the standard deviation above the mode (a measure of compression).

RESULTS

While the modal age of onset is around 85 years among adults with a college degree, the modal age for adults with less than a high school education occurs before age 65 - at least a 20-year difference. The standard deviation of dementia onset is about three times greater for adults with less than a high school education compared to adults with a college degree. Patterns were consistent across race and gender groups.

CONCLUSION

This research highlights the variability of dementia experiences in the older population by documenting differences in longevity without dementia and compression of dementia onset among more educated adults and less educated adults.

CONTRIBUTION

We incorporate conceptual insights from the life span variability and compression literature to better understand education-dementia disparities in both the postponement and uncertainty of dementia onset in the US population.

Biomarkers of Alzheimer's disease in Black and/or African American Alzheimer's Disease Neuroimaging Initiative (ADNI) participants

Majority of dementia research is conducted in non-Hispanic White participants despite a greater prevalence of dementia in other racial groups. To obtain a better understanding of biomarker presentation of Alzheimer's disease (AD) in the non-Hispanic White population, this study exclusively examined AD biomarker abnormalities in 85 Black and/or African American participants within the Alzheimer's Disease Neuroimaging Initiative (ADNI). Participants were classified by the ADNI into 3 clinical groups: cognitively normal, mild cognitive impairment, or dementia. Data examined included demographics, apolipoprotein E (APOE) ε4, cerebrospinal fluid (CSF) Aβ1-42, CSF total tau (t-tau), CSF phosphorylated tau (p-tau), 3T magnetic resonance imaging (MRI), and measures of cognition and function. Analyses of variance and covariance showed lower cortical thickness in 5 of 7 selected MRI regions, lower hippocampal volume, greater volume of white matter hyperintensities, lower measures of cognition and function, lower measures of CSF Aβ1-42, and greater measures of CSF t-tau and p-tau between clinical groups. Our findings confirmed greater AD biomarker abnormalities between clinical groups in this sample.

Evolutionary Selection of APOEɛ4 Encourages Increased Focus on Immunity in Alzheimer's Disease

Smith and Ashford present a compelling hypothesis on evolution of APOE alleles, namely that ɛ4 prevalence is mediated by immune selection pressure against enteric pathogens. While the ɛ3 allele is more prevalent today, it outcompetedɛ4 only relatively recently, as immune selection pressure for more effective immune responses to such pathogens was alleviated with transition to agrarian from hunter-gatherer lifestyles. Smith and Ashford's hypothesis is intriguing in itself, but the implications for APOE ɛ4 function in Alzheimer's disease are even more so and encourage greater focus on specific aspects of immunity in accounting for both ɛ4-mediated and general Alzheimer's disease risk.

APOE ε4 is associated with earlier symptom onset in LOAD but later symptom onset in EOAD

BACKGROUND

We studied the effect of apolipoprotein E (APOE) ε4 status and sex on age of symptom onset (AO) in early- (EO) and late- (LO) onset Alzheimer's disease (AD).

METHOD

A total of 998 EOAD and 2562 LOAD participants from the National Alzheimer's Coordinating Center (NACC) were included. We used analysis of variance to examine AO differences between sexes and APOE genotypes and the effect of APOE ε4, sex, and their interaction on AO in EOAD and LOAD, separately.

RESULTS

APOE ε4 carriers in LOAD had younger AO and in EOAD had older AO. Female EOAD APOE ε4 carriers had older AO compared to non-carriers (P < 0.0001). There was no difference for males. Both male and female LOAD APOE ε4 carriers had younger AO relative to non-carriers (P < 0.0001).

CONCLUSION

The observed earlier AO in EOAD APOE ε4 non-carriers relative to carriers, particularly in females, suggests the presence of additional AD risk variants.

Discrepant modulating effects of dietary docosahexaenoic acid on cerebral lipids, fatty acid transporter expression and soluble beta-amyloid levels in ApoE-/- and C57BL/6J mice

AIMS

The study was designed to explore the role of apolipoprotein E (ApoE) deficiency concomitant with dietary docosahexaenoic acid (DHA) treatment on brain β-amyloid (Aβ) and lipid levels.

METHOD

A 5-month dietary DHA intervention was conducted in ApoE-deficient (ApoE^-/- ) mice and wild-type C57BL/6J (C57 wt) mice. The Morris water maze test was performed to assess the behaviour of the animals. The cortical contents of soluble Aβ_1-40 and Aβ_1-42 were detected by enzyme-linked immunosorbent assay (ELISA). Cortical fatty acid levels were detected by gas chromatography. Gene and protein expression of molecules associated with cerebral Aβ and lipid metabolism were measured using real-time polymerase chain reaction (PCR), Western blot and histological methods.

RESULTS

DHA treatment increased the content of cortical DHA and n-3 polyunsaturated fatty acids (n-3 PUFAs) but decreased the ratio of n-6/n-3 PUFAs in ApoE^-/- mice; whereas the content of cortical DHA and n-3 PUFAs in C57 wt mice remained unchanged after DHA treatment. Cerebral Fabp5 and Cd36 gene expression were significantly downregulated in DHA-fed C57 wt mice; cerebral Cd36 and Scarb1 gene expression were significantly upregulated, whereas Fabp5 gene expression was downregulated in DHA-fed ApoE^-/- mice. In comparison with C57 wt mice, the content of cortical soluble Aβ_1-42 , total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) increased, whereas the level of high-density lipoprotein cholesterol (HDL-C) decreased in ApoE^-/- mice. Interestingly, these differences were significantly reversed by DHA dietary treatment.

CONCLUSION

DHA intervention has discrepant impacts on cerebral lipids, fatty acid transporter expression and soluble Aβ levels in ApoE^-/- and C57 wt mice, suggesting the modifying role of ApoE status on the responses of cerebral lipids and Aβ metabolism to DHA treatment.

APOE ε4 and Alzheimer's disease diagnosis associated differences in L-carnitine, GBB, TMAO, and acylcarnitines in blood and brain

BACKGROUND

The apolipoprotein E (APOE) ε4 allele, involved in fatty acid (FA) metabolism, is a major genetic risk factor for Alzheimer's disease (AD). This study examined the influence of APOE genotypes on blood and brain markers of the L-carnitine system, necessary for fatty acid oxidation (FAO), and their collective influence on the clinical and pathological outcomes of AD.

METHODS

L-carnitine, its metabolites γ-butyrobetaine (GBB) and trimethylamine-n-oxide (TMAO), and its esters (acylcarnitines) were analyzed in blood from predominantly White community/clinic-based individuals (n = 372) and in plasma and brain from the Religious Order Study (ROS) (n = 79) using liquid chromatography tandem mass spectrometry (LC-MS/MS).

FINDINGS

Relative to total blood acylcarnitines, levels of short chain acylcarnitines (SCAs) were higher whereas long chain acylcarnitines (LCAs) were lower in AD, which was observed pre-clinically in APOE ε4s. Plasma medium chain acylcarnitines (MCAs) were higher amongst cognitively healthy APOE ε2 carriers relative to other genotypes. Compared to their respective controls, elevated TMAO and lower L-carnitine and GBB were associated with AD clinical diagnosis and these differences were detected preclinically among APOE ε4 carriers. Plasma and brain GBB, TMAO, and acylcarnitines were also associated with post-mortem brain amyloid, tau, and cerebrovascular pathologies.

INTERPRETATION

Alterations in blood L-carnitine, GBB, TMAO, and acylcarnitines occur early in clinical AD progression and are influenced by APOE genotype. These changes correlate with post-mortem brain AD and cerebrovascular pathologies. Additional studies are required to better understand the role of the FAO disturbances in AD.

Sex-specific biomarkers in Alzheimer's disease progression: Framingham Heart Study

Background

Sex differences in Alzheimer's disease (AD) are not well understood.

Methods

We performed sex-specific analyses of AD and annualized cognitive decline with clinical and blood biomarker data in participants 60+ years old in the community-based longitudinal Framingham Heart Study Offspring Cohort (n = 1398, mean age 68 years, 55% women).

Results

During 11 years of follow-up, women were 96% more likely than men to be diagnosed with clinical AD dementia after adjusting for age and education in the younger age group 60 to 70 years (n = 946; 95% confidence interval [CI], 1.08 to 3.56) although not in the older age group (70+) (n = 452; hazard ratio = 0.98; 95% CI, 0.68 to 1.53). Sex-differences in incident AD rates decreased with increasing levels of education. The total contribution of the biomarkers to AD risk variance was 7.6% in women and 11.7% in men. One unit (pg/ml) lower plasma Aβ42 was associated with 0.0095 unit faster memory decline in women (p = 0.0002) but not in men (p = 0.55) after adjusting for age and education.

Discussion

Our study suggests that both early life and later-life pathological factors may contribute to potential sex differences in incident AD.

Interactions between apolipoprotein E, sex, and amyloid-beta on cerebrospinal fluid p-tau levels in the European prevention of Alzheimer's dementia longitudinal cohort study (EPAD LCS)

Background

Alzheimer's Disease, the leading cause of dementia, is over-represented in females. The apolipoprotein E (APOE)ε4 allele is the strongest genetic risk factor for late-onset AD and is associated with aberrant cerebrospinal fluid levels (CSF) of total tau (t-tau), phosphorylated tau (p-tau), and amyloid-β (Aβ). There is some evidence that sex may mediate the relationship between APOE status and CSF tau, however, evidence is mixed.

Methods

We aimed to examine the interaction between sex, APOE ε4 status, CSF Aβ on t-tau and p-tau in 1599 mid-to-late life individuals without a diagnosis of dementia in the European Prevention of Alzheimer's Dementia (EPAD) longitudinal cohort study.

Findings

We found a significant interaction between APOE status, sex, and CSF Aβ on CSF p-tau levels (β = 0·18, p = 0·04). Specifically, there was a stronger association between APOE status and CSF Aβ₄₂ on CSF p-tau in males compared to females. Further, in females with high Aβ levels (reflecting less cortical deposition), ε4 carriers had significantly elevated p-tau levels relative to non-carriers (W = 39663, p = 0·01). However, there were no significant differences in p-tau between male ε4 carriers and non-carriers with high Aβ (W = 23523, p = 0·64).

Interpretation

An interaction between sex and cerebrospinal fluid Aβ may mediate the relationship between APOE status and CSF p-tau. These data suggest tau accumulation may be independent of Aβ in females, but not males.

Funding

Innovative Medicines Initiative, Swedish Research Council, Alzheimer Drug Discovery Foundation, Swedish Alzheimer Foundation, the Swedish state under the agreement between the Swedish government and the County Councils: the ALF-agreement, and the Alzheimer's Association 2021 Zenith Award.

Association of Genetic Variants Linked to Late-Onset Alzheimer Disease With Cognitive Test Performance by Midlife

IMPORTANCE

Identifying the youngest age when Alzheimer disease (AD) influences cognition and the earliest affected cognitive domains will improve understanding of the natural history of AD and approaches to early diagnosis.

OBJECTIVE

To evaluate the age at which cognitive differences between individuals with higher compared with lower genetic risk of AD are first apparent and which cognitive assessments show the earliest difference.

DESIGN, SETTING, AND PARTICIPANTS

This cross-sectional study used data from UK Biobank participants of European genetic ancestry, aged 40 years or older, who contributed genotypic and cognitive test data from January 1, 2006, to December 31, 2015. Data analysis was performed from March 10, 2020, to January 4, 2022.

EXPOSURE

The AD genetic risk score (GRS), which is a weighted sum of 23 single-nucleotide variations.

MAIN OUTCOMES AND MEASURES

Seven cognitive tests were administered via touchscreen at in-person visits or online. Cognitive domains assessed included fluid intelligence, episodic memory, processing speed, executive functioning, and prospective memory. Multiple cognitive measures were derived from some tests, yielding 32 separate measures. Interactions between age and AD-GRS for each of the 32 cognitive measures were tested with linear regression using a Bonferroni-corrected P value threshold. For cognitive measures with significant evidence of age by AD-GRS interaction, the youngest age of interaction was assessed with new regression models, with nonlinear specification of age terms. Models with youngest age of interaction from 40 to 70 years, in 1-year increments, were compared, and the best-fitting model for each cognitive measure was chosen. Results across cognitive measures were compared to determine which cognitive indicators showed earliest AD-related change.

RESULTS

A total of 405 050 participants (mean [SD] age, 57.1 [7.9] years; 54.1% female) were included. Sample sizes differed across cognitive tests (from 12 455 to 404 682 participants). The AD-GRS significantly modified the association with age on 13 measures derived from the pairs matching (range in difference in mean cognition per decade increase in age for 1-SD higher AD-GRS, 2.5%-11.5%), symbol digit substitution (range in difference in mean cognition per decade increase in age for 1-SD higher AD-GRS, 2.0%-5.8%), and numeric memory tests (difference in mean cognition per decade increase in age for 1-SD higher AD-GRS, 8.8%) (P = 1.56 × 10-3). Best-fitting models suggested that cognitive scores of individuals with a high vs low AD-GRS began to diverge by 56 years of age for all 13 measures and by 47 years of age for 9 measures.

CONCLUSIONS AND RELEVANCE

In this cross-sectional study, by early midlife, subtle differences in memory and attention were detectable among individuals with higher genetic risk of AD.

The close link between brain vascular pathological conditions and neurodegenerative diseases: Focus on some examples and potential treatments

A close relationship is emerging among the age-related neurodegenerative decline, and the age-related typical alterations, dysfunctions, and related diseases of the cerobro-and/or cardiovascular system, which contributes in a significative manner to the triggering and progressing of neurodegenerative diseases (NeuroDegD). Specifically, macroinfarcts, microinfarcts, micro-hemorrhages (and particularly their number), atherosclerosis, arteriolosclerosis and cerebral amyloid angiopathy have been documented to be significantly associated with the onset of the cognitive impairment. In addition, vascular alterations and dysfunctions resulting in a reduced cerebral blood flow, and anomalies in the brain blood barrier (BBB), have been also demonstrated to contribute to NeuroDegD pathophysiologic processes. At the same time, such vascular alterations are also observed in cognitively unimpaired subjects. Here, some of these aspects are described with a particular focus on some NeuroDegD, as well as potential strategies for delaying or stopping their onset and progression.