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Challenging Assumptions About African American Participation in Alzheimer Disease Trials.

ABSTRACT: OBJECTIVE:The authors investigated potential effects of increased African American participation in Alzheimer disease (AD) and mild cognitive impairment (MCI) clinical trials by examining differences in comorbid conditions and treatment outcome affecting trial design. METHODS:Using a meta-database of 18 studies from the Alzheimer's Disease Cooperative Study and the Alzheimer's Disease Neuroimaging Initiative, a cohort of 5,164 subjects were included for whom there were baseline demographic data and information on comorbid disorders, grouped by organ system. Meta-analysis was used to compare prevalence of comorbidities, dropouts, and rates of change on the cognitive subscale of the Alzheimer's Disease Assessment Scale by race. Clinical trial scenarios similar to recent therapeutic trials were simulated to determine effects of increased African American participation on statistical power. RESULTS:Approximately 7% of AD, 4% of MCI, and 11% of normal participants were African American. African American subjects had higher prevalence of cardiovascular disorders (odds ratio: 2.10; 95% confidence interval [CI]: 1.71-2.57) and higher rate of dropouts (odds ratio: 1.60; 95% CI: 1.15-2.21) compared with whites but lower rates of other disorders. There were no significant differences in rate of progression (-0.862 points/year; 95% CI: -1.89 to 0.162) by race and little effect on power in simulated trials with sample sizes similar to current AD trial designs. CONCLUSION:Increasing African American participation in AD clinical trials will require adaptation of trial protocols to address comorbidities and dropouts. However, increased diversity is unlikely to negatively affect trial outcomes and should be encouraged to promote generalizability of trial results.

SUBMITTER: Kennedy RE

PROVIDER: S-EPMC5842064 | biostudies-literature | 2017 Oct

REPOSITORIES: biostudies-literature

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Challenging Assumptions About African American Participation in Alzheimer Disease Trials.

Kennedy Richard E RE Cutter Gary R GR Wang Guoqiao G Schneider Lon S LS

The American journal of geriatric psychiatry : official journal of the American Association for Geriatric Psychiatry 20170425 10

<h4>Objective</h4>The authors investigated potential effects of increased African American participation in Alzheimer disease (AD) and mild cognitive impairment (MCI) clinical trials by examining differences in comorbid conditions and treatment outcome affecting trial design.<h4>Methods</h4>Using a meta-database of 18 studies from the Alzheimer's Disease Cooperative Study and the Alzheimer's Disease Neuroimaging Initiative, a cohort of 5,164 subjects were included for whom there were baseline de ...[more]

PMID: 28554539

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Project description:ImportanceMutations in known causal Alzheimer disease (AD) genes account for only 1% to 3% of patients and almost all are dominantly inherited. Recessive inheritance of complex phenotypes can be linked to long (>1-megabase [Mb]) runs of homozygosity (ROHs) detectable by single-nucleotide polymorphism (SNP) arrays.ObjectiveTo evaluate the association between ROHs and AD in an African American population known to have a risk for AD up to 3 times higher than white individuals.Design, setting, and participantsCase-control study of a large African American data set previously genotyped on different genome-wide SNP arrays conducted from December 2013 to January 2015. Global and locus-based ROH measurements were analyzed using raw or imputed genotype data. We studied the raw genotypes from 2 case-control subsets grouped based on SNP array: Alzheimer's Disease Genetics Consortium data set (871 cases and 1620 control individuals) and Chicago Health and Aging Project-Indianapolis Ibadan Dementia Study data set (279 cases and 1367 control individuals). We then examined the entire data set using imputed genotypes from 1917 cases and 3858 control individuals.Main outcomes and measuresThe ROHs larger than 1 Mb, 2 Mb, or 3 Mb were investigated separately for global burden evaluation, consensus regions, and gene-based analyses.ResultsThe African American cohort had a low degree of inbreeding (F ~ 0.006). In the Alzheimer's Disease Genetics Consortium data set, we detected a significantly higher proportion of cases with ROHs greater than 2 Mb (P = .004) or greater than 3 Mb (P = .02), as well as a significant 114-kilobase consensus region on chr4q31.3 (empirical P value 2 = .04; ROHs >2 Mb). In the Chicago Health and Aging Project-Indianapolis Ibadan Dementia Study data set, we identified a significant 202-kilobase consensus region on Chr15q24.1 (empirical P value 2 = .02; ROHs >1 Mb) and a cluster of 13 significant genes on Chr3p21.31 (empirical P value 2 = .03; ROHs >3 Mb). A total of 43 of 49 nominally significant genes common for both data sets also mapped to Chr3p21.31. Analyses of imputed SNP data from the entire data set confirmed the association of AD with global ROH measurements (12.38 ROHs >1 Mb in cases vs 12.11 in controls; 2.986 Mb average size of ROHs >2 Mb in cases vs 2.889 Mb in controls; and 22% of cases with ROHs >3 Mb vs 19% of controls) and a gene-cluster on Chr3p21.31 (empirical P value 2 = .006-.04; ROHs >3 Mb). Also, we detected a significant association between AD and CLDN17 (empirical P value 2 = .01; ROHs >1 Mb), encoding a protein from the Claudin family, members of which were previously suggested as AD biomarkers.Conclusions and relevanceTo our knowledge, we discovered the first evidence of increased burden of ROHs among patients with AD from an outbred African American population, which could reflect either the cumulative effect of multiple ROHs to AD or the contribution of specific loci harboring recessive mutations and risk haplotypes in a subset of patients. Sequencing is required to uncover AD variants in these individuals.

Project description:The ApoE ?4 allele is the most significant genetic risk factor for late-onset Alzheimer disease. The risk conferred by ?4, however, differs across populations, with populations of African ancestry showing lower ?4 risk compared to those of European or Asian ancestry. The cause of this heterogeneity in risk effect is currently unknown; it may be due to environmental or cultural factors correlated with ancestry, or it may be due to genetic variation local to the ApoE region that differs among populations. Exploring these hypotheses may lead to novel, population-specific therapeutics and risk predictions. To test these hypotheses, we analyzed ApoE genotypes and genome-wide array data in individuals from African American and Puerto Rican populations. A total of 1,766 African American and 220 Puerto Rican individuals with late-onset Alzheimer disease, and 3,730 African American and 169 Puerto Rican cognitively healthy individuals (> 65 years) participated in the study. We first assessed average ancestry across the genome ("global" ancestry) and then tested it for interaction with ApoE genotypes. Next, we assessed the ancestral background of ApoE alleles ("local" ancestry) and tested if ancestry local to ApoE influenced Alzheimer disease risk while controlling for global ancestry. Measures of global ancestry showed no interaction with ApoE risk (Puerto Rican: p-value = 0.49; African American: p-value = 0.65). Conversely, ancestry local to the ApoE region showed an interaction with the ApoE ?4 allele in both populations (Puerto Rican: p-value = 0.019; African American: p-value = 0.005). ApoE ?4 alleles on an African background conferred a lower risk than those with a European ancestral background, regardless of population (Puerto Rican: OR = 1.26 on African background, OR = 4.49 on European; African American: OR = 2.34 on African background, OR = 3.05 on European background). Factors contributing to the lower risk effect in the ApoE gene ?4 allele are likely due to ancestry-specific genetic factors near ApoE rather than non-genetic ethnic, cultural, and environmental factors.

Project description:ImportanceCompared with non-Hispanic White individuals, African American individuals from the same community are approximately twice as likely to develop Alzheimer disease. Despite this disparity, the largest Alzheimer disease genome-wide association studies to date have been conducted in non-Hispanic White individuals. In the largest association analyses of Alzheimer disease in African American individuals, ABCA7, TREM2, and an intergenic locus at 5q35 were previously implicated.ObjectiveTo identify additional risk loci in African American individuals by increasing the sample size and using the African Genome Resource panel.Design, setting, and participantsThis genome-wide association meta-analysis used case-control and family-based data sets from the Alzheimer Disease Genetics Consortium. There were multiple recruitment sites throughout the United States that included individuals with Alzheimer disease and controls of African American ancestry. Analysis began October 2018 and ended September 2019.Main outcomes and measuresDiagnosis of Alzheimer disease.ResultsA total of 2784 individuals with Alzheimer disease (1944 female [69.8%]) and 5222 controls (3743 female [71.7%]) were analyzed (mean [SD] age at last evaluation, 74.2 [13.6] years). Associations with 4 novel common loci centered near the intracellular glycoprotein trafficking gene EDEM1 (3p26; P = 8.9 × 10-7), near the immune response gene ALCAM (3q13; P = 9.3 × 10-7), within GPC6 (13q31; P = 4.1 × 10-7), a gene critical for recruitment of glutamatergic receptors to the neuronal membrane, and within VRK3 (19q13.33; P = 3.5 × 10-7), a gene involved in glutamate neurotoxicity, were identified. In addition, several loci associated with rare variants, including a genome-wide significant intergenic locus near IGF1R at 15q26 (P = 1.7 × 10-9) and 6 additional loci with suggestive significance (P ≤ 5 × 10-7) such as API5 at 11p12 (P = 8.8 × 10-8) and RBFOX1 at 16p13 (P = 5.4 × 10-7) were identified. Gene expression data from brain tissue demonstrate association of ALCAM, ARAP1, GPC6, and RBFOX1 with brain β-amyloid load. Of 25 known loci associated with Alzheimer disease in non-Hispanic White individuals, only APOE, ABCA7, TREM2, BIN1, CD2AP, FERMT2, and WWOX were implicated at a nominal significance level or stronger in African American individuals. Pathway analyses strongly support the notion that immunity, lipid processing, and intracellular trafficking pathways underlying Alzheimer disease in African American individuals overlap with those observed in non-Hispanic White individuals. A new pathway emerging from these analyses is the kidney system, suggesting a novel mechanism for Alzheimer disease that needs further exploration.Conclusions and relevanceWhile the major pathways involved in Alzheimer disease etiology in African American individuals are similar to those in non-Hispanic White individuals, the disease-associated loci within these pathways differ.

Project description:ObjectiveTo elucidate factors that influence African American willingness to participate in health-related research studies.MethodsThe African American Alzheimer disease research study group at North Carolina A&T State University designed an in-person questionnaire and surveyed more than 700 African American adults on their willingness to participate in health-related research studies. The questionnaire was distributed and collected in a nonclinical setting during the years 2008 and 2009. This study was approved by the North Carolina A&T State University Institutional Review Board.ResultsOf the 733 valid respondents, 16% had previously participated in a health-related research study. Of these, more than 90% were willing to participate again in future research studies. Of the 614 who had never participated in a research study, more than 70% expressed willingness to participate. The majority (75%) of experienced research study participants (RSP) were older than 40 years compared with 45% of non-research study participants. Experienced research participants were also twice as likely to have a college degree compared with non-research study participants. Seventy-three percent of non-research study participants were willing to participate in research studies in the future. The factors that were probable impediments to participation included lack of time and trust. Men with knowledge of the Tuskegee Syphilis Study were 50% less likely to be willing to participate compared with those who had not heard of Tuskegee Syphilis Study.ConclusionsAfrican Americans are willing to participate in health-related research studies. Several factors such as the appropriate incentives, community trust building, outreach, and community partnership creation are necessary for engaging minority participants. Incorporating factors that target African American enrollment in research design and implementation, such as increased training of minority health ambassadors and African American researchers and public health specialists, are needed to better engage minorities across generations, in research.

Project description:Increased African-American research participation is critical to the applicability and generalizability of biomedical research, as population diversity continues to increase both domestically and abroad. Yet numerous studies document historical origins of mistrust, as well as other barriers that may contribute to resistance in the African-American community towards participation in biomedical research. However, a growing body of more recent scientific evidence suggests that African-Americans value research and are willing to participate when asked. In the present study, we set out to determine factors associated with research participation of African-American families in postmortem human brain tissue donation for neuropsychiatric disorders as compared with Caucasian families, from same-day medical examiner autopsy referrals. We retrospectively reviewed brain donation rates, as well as demographic and clinical factors associated with donation in 1,421 consecutive referrals to three medical examiner's offices from 2010-2015. Overall, 69.7% of all next-of-kin contacted agreed to brain donation. While Caucasian families consented to donate brain tissue at a significantly higher rate (74.1%) than African-American families (57.0%) (p<0.001), African-American brain donation rates were as high as 60.5% in referrals from Maryland. Neither African-American nor Caucasian donors differed significantly from non-donors on any demographic or clinical factors ascertained, including age, sex, diagnosis of the donor, or in the relationship of the next-of-kin being contacted (p>0.05). However, Caucasian donors were significantly older, had more years of education, were more likely to be referred for study due to a psychiatric diagnosis, more likely to have comorbid substance abuse, and more likely to have died via suicide, as compared with African-American donors (p<0.05). When African-American participants are identified and approached, African-American families as well as Caucasian families are indeed willing to donate brain tissue on the spot for neuropsychiatric research, which supports the belief that African-American attitudes towards biomedical research may be more favorable than previously thought.

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Challenging Assumptions About African American Participation in Alzheimer Disease Trials.

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Challenging Assumptions About African American Participation in Alzheimer Disease Trials.

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