Baseline levels and longitudinal rates of change in plasma Aβ42/40 among self-identified Black/African American and White individuals

Objective

The use of blood-based biomarkers of Alzheimer disease (AD) may facilitate access to biomarker testing of groups that have been historically under-represented in research. We evaluated whether plasma Aβ42/40 has similar or different baseline levels and longitudinal rates of change in participants racialized as Black or White.

Methods

The Study of Race to Understand Alzheimer Biomarkers (SORTOUT-AB) is a multi-center longitudinal study to evaluate for potential differences in AD biomarkers between individuals racialized as Black or White. Plasma samples collected at three AD Research Centers (Washington University, University of Pennsylvania, and University of Alabama-Birmingham) underwent analysis with C2N Diagnostics' PrecivityAD™ blood test for Aβ42 and Aβ40. General linear mixed effects models were used to estimate the baseline levels and rates of longitudinal change for plasma Aβ measures in both racial groups. Analyses also examined whether dementia status, age, sex, education, APOE ε4 carrier status, medical comorbidities, or fasting status modified potential racial differences.

Results

Of the 324 Black and 1,547 White participants, there were 158 Black and 759 White participants with plasma Aβ measures from at least two longitudinal samples over a mean interval of 6.62 years. At baseline, the group of Black participants had lower levels of plasma Aβ40 but similar levels of plasma Aβ42 as compared to the group of White participants. As a result, baseline plasma Aβ42/40 levels were higher in the Black group than the White group, consistent with the Black group having lower levels of amyloid pathology. Racial differences in plasma Aβ42/40 were not modified by age, sex, education, APOE ε4 carrier status, medical conditions (hypertension and diabetes), or fasting status. Despite differences in baseline levels, the Black and White groups had a similar longitudinal rate of change in plasma Aβ42/40.

Interpretation

Black individuals participating in AD research studies had a higher mean level of plasma Aβ42/40, consistent with a lower level of amyloid pathology, which, if confirmed, may imply a lower proportion of Black individuals being eligible for AD clinical trials in which the presence of amyloid is a prerequisite. However, there was no significant racial difference in the rate of change in plasma Aβ42/40, suggesting that amyloid pathology accumulates similarly across racialized groups.

ADVERSE SOCIAL EXPERIENCES, SOCIAL SUPPORT, AND HEALTH OUTCOMES AMONG BLACK AND WHITE FAMILY CAREGIVERS

Family caregivers provide care for loved ones who have difficulty performing activities of daily living. Previous research has examined the influence of direct and indirect stressors on caregiver’s health outcomes but has often neglected the role of tertiary stressors (stressors that are not caused by caregiving but influence caregivers’ appraisals of stress). This study examined the impact of tertiary stressors called adverse social experiences (ASEs), including negative interaction (criticism from others, excessive demands by others, being taken advantage of, and others prying into caregivers’ personal affairs), experiences of discrimination, and low physician trust on caregiver health outcomes including depressive symptoms along with mental and physical health quality of life (QoL). This study also investigated the effects of social support on health outcomes in caregivers. Linear regression models were used to analyze these relationships within a group of 56 Black and White adult caregivers (18+) recruited online via social media and listservs from April to June 2021. Caregivers provided at least 5 hours of care weekly for recipients aged at least 45 years old. Negative interaction predicted more depressive symptoms, whereas emotional support and satisfaction with support were predictors of less depressive symptoms and better mental health QoL (p’s < .05). Experiences of discrimination and physician trust did not predict health outcomes. These findings suggest researchers should further investigate the impact of ASEs, particularly negative interaction, on caregiver health. Healthcare providers of caregivers should consider how ASEs and social support may affect caregivers’ health and ability to care for their relatives.

Piloting the Effectiveness of a Text Messaging and Fitness Tracking Intervention within Older Black Women

Physical activity (PA) can help lower risk of obesity and type 2 diabetes, reduce anxiety, and reduce risk of Alzheimer’s and other related dementias. Despite these benefits, older, obese Black women are not meeting CDC recommended PA guidelines at disproportionate rates. This study aims to identify whether a targeted intervention, Texting Older Sisters to Step (T.O.S.S.), can improve health-related outcomes within older Black women. A sample of 24 Black women (12 per group) age 60 and older who had a BMI > 30 were recruited. The treatment group received text messages previously validated to promote physical activity every day for 12-weeks and were placed in Fitbit communities. The control group received a general health or nutrition-related text message every Sunday. Participants ranged from 60 to 70 years of age with a mean of 64 and 90% had at least some college education. Overall, there was a significant reduction of 1.53 inches in waist circumference, p < .01. When the groups were compared, the treatment group showed a 2.16 inch reduction compared to a 0.91 inch reduction in the control group (Cohen’s d=0.54, a medium effect size). Similarly, the treatment group lost 2.50 pounds on average compared to 1.33 in the control group (d=0.23). When the groups were compared on HgA1c, the treatment group was stable with a reduction of 0.01 unit whereas the control group reduction was 0.15 unit (d=0.23). Findings provide initial support for the T.O.S.S. intervention and suggest a modification of including nutrition information among the intervention messages.

Understanding Driving Avoidance Among Older African Americans And Whites With Diabetes

Diabetes mellitus is one of the most common chronic diseases with half of the new diagnoses affecting adults aged 60 years and older. Although African Americans are more likely to develop the disease, they are also less likely to receive healthcare. Importantly, living with diabetes is likely to negatively impact mobility for aging adults as the disease is associated with lower physical functioning (e.g., ability to maintain one’s balance). Further, diabetes could pose a significant threat to a person with diabetes’ ability to drive and remain in the community. This study examines the relationships and influences of social determinants of health (e.g., race, gender, socioeconomic status) and cognition on avoiding driving maneuvers such as driving at night and in rush hour traffic among older adults with diabetes. Data from the University of Alabama at Birmingham (UAB) Diabetes and Aging Study of Health (DASH) were analyzed and of the 224 participants, 193 (86.16%) were current drivers. There was a gender difference with 94.12% of males and 79.51% of females being current drivers, p < .01. Within the sample of current drivers, 45% were African American and being female, not married, lower levels of education and cognition, low income, and being African American were associated with higher scores on driving avoidance. Cognition explained 30.44% of the racial difference in driving avoidance. Findings from this study will help identify individuals who are at-risk for reduced mobility and identify those who may need to be intervened upon to support a better quality of life.

Texting Older Sisters to Step (TOSS) Using Fitbits to Promote Physical Activity: A Feasibility Study

Black women are disproportionately diagnosed with obesity (BMI ≥ 30 kg/m2). Obesity is a preventable but complex, public health problem that is multifaceted, chronic, and approximately 58% of Black women 60 years and older are classified as obese, compared to 38% of their White counterparts. This 12 week, pre/post, 2-group study aimed to determine if a peer-informed physical activity (PA) intervention with peer support would be feasible among community- dwelling, obese, older Black women to promote regular PA. Forty-eight potential participants were screened, 24 categorized as obese were enrolled and completed the study. The mean age was 64 (SD 3.0) years. Steps were measured by a Fitbit-Inspire with data successfully collected on 98% of days with the treatment group averaging a daily increase of 700-steps more than the control. Evaluation of intervention’s acceptability revealed that 100% enjoyed the study and using the Fitbit device. Text message readability was 100% and 95% said the study was motivational. Additionally, 8.3% said daily prompts were too frequent, 12% indicated that future studies should include additional social support, and 88% did not comment on the Fitbit community option for support, suggesting that this feature was not practical. Findings demonstrated that this intervention meets the criteria of being scalable, low cost, feasible, and acceptable for the older Black women. Using self-monitoring techniques in combination with at least one other behavioral strategy, such as our TOSS messages (cues for motivation) as the delivery channel for health promotion messages are a promising approach to increase PA behaviors.

Interest in Supportive Services Among Black Working and Non-Working Caregivers in the Deep South

The current investigation provides information on supportive services caregivers said they would be interested in if they were made available. Participants were recruited from the Birmingham, AL metro area and received a $25 gift card for completing a telephone interview. Of the 38 caregivers enrolled, 18 (47.37%) reported being currently employed and working an average of 33.92 hours per week (range = 5 – 60). Participants were caring for individuals with average scores on the AD8 Dementia Screening Scale of 7.3 and 10.4 on the Clinical Dementia Scale Sum of Boxes (above the cutoffs for probable dementia). Thirty-three caregivers (87%) reported being interested in at least one of the services listed with differences observed for services that would be preferred by working vs. non-working caregivers. These data will be utilized to provide initial support for a multicomponent intervention that may be effective in reducing negative outcomes within Black caregivers.

IADL DIFFICULTY AND MORTALITY IN ACTIVE: IMPLICATIONS FOR TRANSFER OF COGNITIVE TRAINING

Objectives: Our goals were to externally scale an IADL difficulty scale to the more recognizable Functional Activities Questionnaire (FAQ), and test whether cognitive training attenuates the relationship between IADL difficulty and mortality. Method: We leveraged externally available FAQ data from NACC to scale questions about IADL activities administered in ACTIVE (N=2,802) using item response theory. We modeled time to death as a function of IADL difficulty in ACTIVE using survival analysis, testing whether ACTIVE intervention group status modified the association between FAQ and mortality. Results: IADL difficulty in ACTIVE, scaled to the FAQ, was associated with a higher risk of death (Hazard Ratio, HR, 1.01, 95% Confidence Interval, CI: 1.001, 1.02). The relationship did not differ by ACTIVE intervention status. Discussion: Cognitive training does not modify the relationship between IADL difficulty and mortality, consistent with a hypothesis that proposed relationships between cognitive ability and IADL difficulty are correlational, not causal.

Meta-analysis of cognitive performance in fibromyalgia

INTRODUCTION

Fibromyalgia is a condition with symptoms of pain, physical function difficulties, and emotional problems, but is also characterized by complaints of poor cognition (often called "FibroFog"). Over the last two decades, a number of studies have examined cognitive differences between individuals with and without fibromyalgia. The purpose of the current study was to conduct a quantitative synthesis of these differences across multiple cognitive domains.

METHOD

Following Cochrane guidelines, we identified 37 eligible studies for analysis where persons with fibromyalgia (total n = 964) were compared to participants from age-matched control groups without fibromyalgia (total n = 1025) on a range of neuropsychological measures. Group differences between persons with fibromyalgia and healthy controls were examined for cognitive domains including processing speed, long- and short-term memory, and executive functions (inhibitory control, set shifting, updating, and accessing). Random-effect meta-analyses were conducted to determine effect sizes for these differences in cognitive performance.

RESULTS

Fibromyalgia was significantly and negatively associated with performance on all domains of cognitive function. The largest effect size was found for inhibitory control (g = 0.61), followed by memory (g = 0.51 for short-term, 0.50 for long-term memory). The smallest cognitive difference between those with fibromyalgia and controls was for set shifting (g = 0.30).

CONCLUSION

These findings support the hypothesis that the self-reported cognitive impact of fibromyalgia is also found in objective neuropsychological measures. Routine screening for cognitive dysfunction in those with fibromyalgia may be warranted in addition to assessment of the traditional fibromyalgia symptoms.

Predictors of Time to Nursing Home Placement in White and African American Individuals With Dementia

Objective: This study examined the influence of racial group identification on nursing home placement (NHP) for individuals with dementia before and after adjusting for the possible mediating effects of the caregiving context as defined by stressprocess variables in 215 caregiver/care recipient dyads. Method: Demographics, problem behaviors, self-care impairment, and caregiver appraisal, social support, psychological well-being, and coping were used to prospectively predict Time to NHP. Results: Race was a significant predictor of NHP with African American care recipients placed significantly slower than White care recipients. Race remained a significant predictor of Time to NHP after controlling for other variables that showed independent association with Time to NHP and stress-process variables. Discussion: Findings suggest that stress-process variables are critical factors in Time to NHP; however, these variables do not explain fully the difference in Time to NHP seen in White and African American care recipients.

Surrounding community residents' expectations of HOPE VI for their community, health and physical activity

Using a community-engaged participatory research approach, this study identified surrounding community residents' expectations for how a HOPE VI housing initiative might affect their community and individual health and physical activity. Fifty-nine women and men engaged in concept mapping, which is a mixed methods approach, where participants generate, sort, and rate ideas. Participants generated 197 unique statements. Thirteen thematic clusters related to expected changes for the community, health and physical activity emerged. Residents' rated 'Increased Pride in the Neighborhood' and 'Increased Safety' as the most important factors related to HOPE VI whereas 'Drawbacks of HOPE VI' was rated as least important. This research provides insight into the potential impacts of housing initiatives from the perspective of those most affected by such initiatives. The findings also highlight environmental changes as potential mechanisms that may improve residents' perceptions of the community and encourage healthy lifestyles.

The influence of HOPE VI neighborhood revitalization on neighborhood-based physical activity: A mixed-methods approach

OBJECTIVES

This study uses a mixed methods approach to 1) identify surrounding residents' perceived expectations for Housing Opportunities for People Everywhere (HOPE VI) policy on physical activity outcomes and to 2) quantitatively examine the odds of neighborhood-based physical activity pre-/post-HOPE VI in a low socioeconomic status, predominantly African American community in Birmingham, Alabama.

METHODS

To address aim one, we used group concept mapping which is a structured approach for data collection and analyses that produces pictures/maps of ideas. Fifty-eight residents developed statements about potential influences of HOPE VI on neighborhood-based physical activity. In the quantitative study, we examined whether these potential influences increased the odds of neighborhood walking/jogging. We computed block entry logistic regression models with a larger cohort of residents at baseline (n = 184) and six-months (n = 142, 77% retention; n = 120 for all informative variables). We examined perceived neighborhood disorder (perceived neighborhood disorder scale), walkability and aesthetics (Neighborhood Environment Walkability Scale) and HOPE VI-related community safety and safety for physical activity as predictors.

RESULTS

During concept mapping, residents generated statements that clustered into three distinct concepts, "Increased Leisure Physical Activity," "Safe Play Areas," and "Generating Health Promoting Resources." The quantitative analyses indicated that changes in neighborhood walkability increased the odds of neighborhood-based physical activity (p = 0.04). When HOPE VI-related safety for physical activity was entered into the model, it was associated with increased odds of physical activity (p = 0.04). Walkability was no longer statistically significant.

CONCLUSIONS

These results suggest that housing policies that create walkable neighborhoods and that improve perceptions of safety for physical activity may increase neighborhood-based physical activity. However, the longer term impacts of neighborhood-level policies on physical activity require more longitudinal evidence to determine whether increased participation in physical activity is sustained.

Standard deviations and correlations of GC levels in DNA sequences

In a DNA sequence that exhibits long-range correlations, standard deviations among the GC levels of its segments can be up to an order of magnitude higher than in a sequence consisting of independent, identically distributed nucleotides. Conversely, plots of inter-segment standard deviations vs. segment length reveal quantitative information about the correlations present in a sequence. We present and discuss formulae that relate long-range (power-law) correlations between the nucleotides of a sequence to the expected standard deviations of the GC levels of its segments, and to the correlations between them.

Compositional heterogeneity within and among isochores in mammalian genomes. I. CsCl and sequence analyses

GC level distributions of a species' nuclear genome, or of its compositional fractions, encode key information on structural and functional properties of the genome and on its evolution. They can be calculated either from absorbance profiles of the DNA in CsCl density gradients at sedimentation equilibrium, or by scanning long contigs of largely sequenced genomes. In the present study, we address the quantitative characterization of the compositional heterogeneity of genomes, as measured by the GC distributions of fixed-length fragments. Special attention is given to mammalian genomes, since their compartmentalization into isochores implies two levels of heterogeneity, intra-isochore (local) and inter-isochore (global). This partitioning is a natural one, since large-scale compositional properties vary much more among isochores than within them. Intra-isochore GC distributions become roughly Gaussian for long fragments, and their standard deviations decrease only slowly with increasing fragment length, unlike random sequences. This effect can be explained by 'long-range' correlations, often overlooked, that are present along isochores.

Compositional heterogeneity within and among isochores in mammalian genomes. II. Some general comments

The presence of long-range correlations and/or mosaicism in DNA sequences results in GC fluctuations, even within individual isochores that are much larger than expected correlation-free 'random' sequences. Neglecting the presence of such fluctuations can lead to incorrect conclusions regarding relative homogeneity or isochore borders. In this commentary, we address these and other methodological issues raised by the variations in GC level within human isochores. We also discuss some recent misconceptions.

Diversity and phylogenetic implications of CsCl profiles from rodent DNAs

Buoyant density profiles of high-molecular-weight DNAs sedimented in CsCl gradients, i.e., compositional distributions of 50- to 100-kb genomic fragments, have revealed a clear difference between the murids so far studied and most other mammals, including other rodents. Sequence analyses have revealed other, related, compositional differences between murids and nonmurids. In the present study, we obtained CsCl profiles of 17 rodent species representing 13 families. The modal buoyant densities obtained for rodents span the full range of values observed in other eutherians. More remarkably, the skewness (asymmetry, mean - modal buoyant density) of the rodent profiles extends to values well below those of other eutherians. Scatterplots of these and related CsCl profile parameters show groups of rodent families that agree largely with established rodent taxonomy, in particular with the monophyly of the Geomyoidea superfamily and the position of the Dipodidae family within the Myomorpha. In contrast, while confirming and extending previously reported differences between the profiles of Myomorpha and those of other rodents, the CsCl data question a traditional hypothesis positing Gliridae within Myomorpha, as does the recently sequenced mitochondrial genome of dormouse. Analysis of CsCl profiles is presented here as a rapid, robust method for exploring rodent and other vertebrate systematics.

The gene distribution of the human genome

Linear correlations exist between the GC levels of third codon positions (GC3) of individual human genes and the GC levels of long genomic sequences and DNA molecules (50-100 kb in size) embedding the genes. These linear relationships allow the positioning of the GC3 histogram of cDNA sequences from the databases relative to the CsCl profile of human DNA. In turn, this allows an estimate of the relative concentrations of genes in genomic regions of different GC content. An estimate obtained by using current sequence data and Gaussian decompositions of the GC3 histogram and of the CsCl profile indicates that the GC-richest (non-ribosomal) component of the human genome is at least 17 times as gene-rich as the GC-poor regions. Moreover, our results suggest that the most recent physical maps of the human genome consisting of overlapping YACs cover less than 50% of the genes.

Human coding and noncoding DNA: compositional correlations

As the correlations between GC levels in third codon positions (GC3) and intergenic sequence GC levels can be used to assess the distribution of genes in the human genome, they were studied in detail. Previous work from our laboratory has demonstrated the existence of linear correlations between GC levels of exons, introns, third codon positions, 5' flanking regions of genes, and long genomic DNA sequences (> or = 10 kb) or DNA molecules (50-100 kb) in which the genes are embedded. The present study confirms and extends the previous results using a larger set of data. Furthermore, an analysis of 4270 human genomic DNA and cDNA sequences has allowed us to confirm a correlation of GC3 against GC1+2. Recent additions to the sequence database have also allowed separate analyses of the 5' flanking regions of CpG island and non-CpG island genes as well as analyses of 3' flanking regions, which suggest that the GC levels of 3' flanking regions are closer to those of intergenic DNA than are those of other regions of genes.

Periodicity of eight nucleotides in purine distribution around human genomic CpG dinucleotides

Mammalian genomes, unlike the genomes of Drosophila and yeast, are characterized by CpG methylation and concomitant CpG depletion, which is caused by the enhanced mutation rate of 5-methylcytosine. To find out whether local nucleotide sequences around existing methylated CpG dinucleotides have common patterns, we analyzed a large population of CpG-poor regions in human DNA, which are typically methylated. We detected a novel periodic variation in the numbers of purine bases around CpGs in the noncoding parts of these sequences. This periodicity of eight nucleotides gradually diminished over 64 nucleotides on each side of the central CpG. Furthermore, the frequencies of the 5' and 3' nearest neighbors of CpGs in CpG-poor regions were biased towards cytosine and guanine, respectively. Such biased sequence contexts may have helped to stabilize CpGs against depletion during mammalian evolution.

Short introns interrupting the Oct-2 POU domain may prevent recombination between POU family genes without interfering with potential POU domain 'shuffling' in evolution

Transcription factors are often encoded by gene families that share the same type of DNA binding domain. The POU domain genes are one such paradigm. We compared the genomic DNA encoding the POU domain of the Oct-2 genes in human and mouse. In both species this domain is split into a cluster of four exons by short, highly diverged introns. We postulate that the main role of these introns is to prevent ectopic homologous recombination with other members of the POU gene family, with its potentially deleterious effects in somatic and germline cells. Such rapidly diverging introns may generally promote evolution by facilitating the maintenance of duplicated genes. The use of different codons for the same protein domain among members of a gene family may be a slower process that serves a similar purpose. Introns that split conserved domains such as the POU domain do not conform to the exon shuffling hypothesis originally put forward by W. Gilbert (1978). However, we note that the introns flanking the POU domain are in the same phase, i.e. interrupt codons in the same reading frame. Thus we propose that the entire POU domain, which is encoded by a tight cluster of exons, has been shuffled together during evolution as a functional unit, or 'shufflon'.

Evidence for erosion of mouse CpG islands during mammalian evolution

In housekeeping and many tissue-specific genes, the promoter is embedded in a so-called CpG island. We have compared the available human and mouse DNA sequences with respect to their CpG island properties. While mouse sequences showed a simple gradient distribution of G + C content and CpG densities, man had a distinct peak of sequences with typical CpG island characteristics. Pairwise comparison of 23 orthologous genes revealed that mouse almost always had a less pronounced CpG island than man, or none at all. In both species the requirements for a functional CpG island may be similar in that most DNA regions with a density of six or more CpG per 100 bp remain unmethylated. However, the mouse has apparently experienced more accidental CpG island methylation, suggested by local TpG and CpA excess. We propose that: (1) in mouse the CpG islands do not represent the ancestral state but have been eroded during evolution, and (2) this erosion may be related to the mouse's small body mass and short life-span, allowing for a more relaxed control of gene activity.