Effect of genetic testing for risk of Alzheimer's disease

Cardiovascular health, genetic risk, and risk of dementia in the Framingham Heart Study

OBJECTIVE

To determine the joint role of ideal cardiovascular health (CVH) and genetic risk on risk of dementia.

METHODS

We categorized CVH on the basis of the American Heart Association Ideal CVH Index and genetic risk through a genetic risk score (GRS) of common genetic variants and the APOE ε4 genotype in 1,211 Framingham Heart Study (FHS) offspring cohort participants. We used multivariable Cox proportional hazards regression models to examine the association between CVH, genetic risk, and incident all-cause dementia with up to 10 years of follow-up (mean 8.4 years, 96 incident dementia cases), adjusting for age, sex, and education.

RESULTS

We observed that a high GRS (>80th percentile) was associated with a 2.6-fold risk of dementia (95% confidence interval [CI] of hazard ratio [HR] 1.23-5.29; p = 0.012) compared with having a low GRS (<20th percentile); carrying at least 1 APOE ε4 allele was associated with a 2.3-fold risk of dementia compared with not carrying an APOE ε4 allele (95% CI of HR 1.49-3.53; p = 0.0002), and having a favorable CVH showed a 0.45-fold lower risk of dementia (95% CI of HR 0.20-1.01; p = 0.0527) compared to having an unfavorable CVH when all 3 components were included in the model. We did not observe an interaction between CVH and GRS (p = 0.99) or APOE ε4 (p = 0.16).

CONCLUSIONS

We observed that both genetic risk and CVH contribute additively to dementia risk.

Correlation of gene polymorphisms of CD36 and ApoE with susceptibility of Alzheimer disease: A case-control study

This research was aimed to explore correlation of gene polymorphisms of CD36 and ApoE with susceptibility of Alzheimer disease (AD).This study was a case-control study. Two hundred eleven AD hospitalized patients were selected as the AD group and 241 subjects were selected as the control group. PCR-RFLP was used to detect three loci (rs7755, rs3211956, and rs10499859) of CD36 gene and ApoE genotype. Chi-square test and univariate nonconditional logistic regression analysis were used to calculate the odds ratio (OR) and 95% confidence interval (95% CI). The haplotypes were constructed using SHEsis online software and the correlation between haplotypes and AD was analyzed. Meanwhile, differences of 3 alleles of ApoE and 6 genotypes (E2/E2, E2/E3, E2/E4, E3/E3, E3/E4, E4/E4) were compared between AD and control groups.The frequencies of rs7755 genotype (χ = 10.780, P = .005) and allele (χ = 10.549, P = .001) were statistically different between 2 groups. The genotype frequency of rs3211956 was statistically different between AD and control groups (χ = 10.119, P = .006). For the rs7755 locus, GG genotype (OR: 2.013, 95% CI: 1.098-3.699) was an independent risk factor for AD compared with AA genotype. In the dominant model, the risk to develop AD in AG/GG genotype was 1.686 times higher than AA genotype. For the rs3211956 locus, compared with TT genotype, GT genotype (OR: 0.536, 95% CI: 0.340-0.846) was a protective factor for AD after adjusting various physiological and biochemical factors. In the dominant model, the risk of GT/GG genotype to develop AD was reduced by 41.6%. For ApoE gene, the distribution differences of E2/E3 (χ = 9.216, P = .002), E3/E4 (χ = 7.728, P = .005), and E4/E4 had statistical significance between the 2 groups. The frequencies of allele E2 (χ = 9.359, P = .002) and E4 (χ = 13.995, P < .001) were statistically significant between AD and control groups.The rs7755 and rs3211956 loci polymorphisms of CD36 gene and genotype E2/E3, E3/E4, E4/E4 of ApoE gene, and E2 and E4 alleles were statistically related with AD.

The integration of epigenetics and genetics in nutrition research for CVD risk factors

There is increasing evidence documenting gene-by-environment (G × E) interactions for CVD related traits. However, the underlying mechanisms are still unclear. DNA methylation may represent one of such potential mechanisms. The objective of this review paper is to summarise the current evidence supporting the interplay among DNA methylation, genetic variants, and environmental factors, specifically (1) the association between SNP and DNA methylation; (2) the role that DNA methylation plays in G × E interactions. The current evidence supports the notion that genotype-dependent methylation may account, in part, for the mechanisms underlying observed G × E interactions in loci such asAPOE, IL6and ATP-binding cassette A1. However, these findings should be validated using intervention studies with high level of scientific evidence. The ultimate goal is to apply the knowledge and the technology generated by this research towards genetically based strategies for the development of personalised nutrition and medicine.

The gen-ethics bowl - an in-class activity combining genetics and bioethics

Undergraduate science professors are capable of teaching the scientific principles behind new genetic technologies. However, they are not often readied to explore the ethical and social implications. We created an ethics bowl that brings together students in genetic and healthcare ethics courses to analyze ethical issues in genetics. It is an engaging, challenging, and rewarding experience that provides students with the tools to identify ethical elements in science. This proves to be a wonderful first step in training morally sensitive scientists.

Effect of knowledge of APOE genotype on subjective and objective memory performance in healthy older adults

OBJECTIVE

The knowledge that one carries the apolipoprotein E (APOE) ε4 allele risk factor for Alzheimer's disease was recently found to have little short-term psychological risk. The authors investigated the impact of knowledge of carrying the risk allele on subjective ratings of memory and objective memory test performance of older adults.

METHOD

Using a nested case-control design, the authors administered objective verbal and visual memory tests and self-rating scales of memory function to 144 cognitively normal older adults (ages 52-89) with known APOE genotype who knew (ε4+, N=25; ε4-, N=49) or did not know (ε4+, N=25; ε4-, N=45) their genotype and genetic risk for Alzheimer's disease prior to neuropsychological evaluation.

RESULTS

Significant genotype-by-disclosure interaction effects were observed on several memory rating scales and tests of immediate and delayed verbal recall. Older adults who knew their ε4+ genotype judged their memory more harshly and performed worse on an objective verbal memory test than did ε4+ adults who did not know. In contrast, older adults who knew their ε4- genotype judged their memory more positively than did ε4- adults who did not know, but these groups did not differ in objective memory test performance.

CONCLUSIONS

Informing older adults that they have an APOE genotype associated with an increased risk of Alzheimer's disease can have adverse consequences on their perception of their memory abilities and their performance on objective memory tests. The patient's knowledge of his or her genotype and risk of Alzheimer's disease should be considered when evaluating cognition in the elderly.

Patient accounts of diagnostic testing for familial hypercholesterolaemia: comparing responses to genetic and non-genetic testing methods

Background

Continuing developments in genetic testing technology together with research revealing gene-disease associations have brought closer the potential for genetic screening of populations. A major concern, as with any screening programme, is the response of the patient to the findings of screening, whether the outcome is positive or negative. Such concern is heightened for genetic testing, which it is feared may elicit stronger reactions than non-genetic testing.

Methods

This paper draws on thematic analysis of 113 semi-structured interviews with 39 patients being tested for familial hypercholesterolaemia (FH), an inherited predisposition to early-onset heart disease. It examines the impact of disease risk assessments based on both genetic and non-genetic information, or solely non-genetic information.

Results

The impact of diagnostic testing did not seem to vary according to whether or not genetic information was used. More generally, being given a positive or negative diagnosis of FH had minimal discernible impact on people's lives as they maintained the continuity of their beliefs and behaviour.

Conclusions

The results suggest that concerns about the use of genetic testing in this context are unfounded, a conclusion that echoes findings from studies in this and other health contexts.

[Ethical considerations in the presymptomatic diagnosis of Alzheimer's disease]

Research into the human genome has undoubtedly opened up a new perspective in medicine. The ability to identify the cause of specific diseases, especially neurodegenerative diseases, will definitively change the concepts of disease and treatment, while advances such as antibiotic therapy and anesthesia will be relegated to history. However, the arrival of genome medicine poses major bioethical challenges, many of which remain to be resolved. We review the applicability, results and consequences of predictions based on genetic tests for presymptomatic Alzheimer's disease, as well as the dilemmas and contradictions that are already arising as a result of the commercialization of predictive tests for public use with little or no medical supervision. Given that there is currently no effective treatment of Alzheimeŕs disease, the greatest challenge and contradiction lies in managing the results of predictive tests. There are no indications for the performance of predictive genetic tests in late or sporadic Alzheimer's disease or for counselling of persons requesting these tests. The PICOGEN program provides a safe, effective, reliable and satisfactory option for persons requesting these tests who meet the inclusion criteria. Currently, caution should be the norm when considering the performance of predictive tests in presymptomatic dementia.

Emotional impact of screening: a systematic review and meta-analysis

BACKGROUND

There is a widely held expectation that screening for disease has adverse emotional impacts. The aim of the current review is to estimate the short (< 4 weeks) and longer term (> 4 weeks) emotional impact of such screening.

METHODS

Studies selected for inclusion were (a) randomised controlled trials in which (b) participants in one arm underwent screening and received test results, and those in a control arm did not, and (c) emotional outcomes were assessed in both arms. MEDLINE via PubMed (1950 to present), EMBASE (1980 to present), PsycINFO (1985 to present) using OVID SP, and CINAHL (1982 to present) via EBSCO were searched, using strategies developed with keywords and medical subject headings. Data were extracted on emotional outcomes, type of screening test and test results.

RESULTS

Of the 12 studies that met the inclusion criteria, six involved screening for cancer, two for diabetes, and one each for abdominal aortic aneurysms, peptic ulcer, coronary heart disease and osteoporosis. Five studies reported data on anxiety, five [corrected] on depression, two on general distress and eight on quality of life assessed between one week and 13 years after screening (median = 1.3 years).Meta-analyses revealed no significant impact of screening on longer term anxiety (pooled SMD 0.01, 95% CI -0.10, 0.11), depression (pooled SMD -0.04, 95% CI -.12, 0.20), or quality of life subscales (mental and self-assessed health pooled SMDs, respectively: 0.03; -0.01, (95% CI -.02, 0.04; 0.00, 95% CI -.04, 0.03).

CONCLUSION

Screening does not appear to have adverse emotional impacts in the longer term (> 4 weeks). Too few studies assessed outcomes before four weeks to comment on the shorter term emotional impact of screening.

Role of genomics in cardiovascular medicine

As all branches of science grow and new experimental techniques become readily accessible, our knowledge of medicine is likely to increase exponentially in the coming years. Recently developed technologies have revolutionized our analytical capacities, leading to vast knowledge of many genes or genomic regions involved in the pathogenesis of congenital heart diseases, which are often associated with other genetic syndromes, coronary artery disease and non-ischemic cardiomyopathies and channelopathies. The knowledge-base of the genesis of cardiovascular diseases is likely going to be further revolutionized in this new era of genomic medicine. Here, we review the advances that have been made over the last several years in this field and discuss different genetic mechanisms that have been shown to underlie a variety of cardiovascular diseases.

Debating clinical utility

The clinical utility of genetic tests is determined by the outcomes following test use. Like other measures of value, it is often contested. Stakeholders may have different views about benefits and risks and about the importance of social versus health outcomes. They also commonly disagree about the evidence needed to determine whether a test is effective in achieving a specific outcome. Questions may be presented as factual disagreements, when they are actually debates about what information matters or how facts should be interpreted and used in clinical decision-making. Defining the different issues at stake is therefore an important element of policy-making. Key issues include evidence standards for test use, and in particular, the circumstances under which prospective controlled data should be required, as well as evidence on feasibility, cost and equitable delivery of testing; the goals of population-based screening programs, and in particular, the role of social outcomes in evaluating test value; and the appropriate uses and funding of tests that inform non-medical actions. Addressing each of these issues requires attention to stakeholder values and methods for effective deliberation that incorporate consumer as well as health professional perspectives.