Estimating and disclosing the risk of developing Alzheimer's disease: challenges, controversies and future directions

Biomarker-Based Risk Prediction of Alzheimer’s Disease Dementia in Mild Cognitive Impairment: Psychosocial, Ethical, and Legal Aspects

Background: Today, a growing number of individuals with mild cognitive impairment (MCI) wish to assess their risk of developing Alzheimer’s disease (AD) dementia. The expectations as well as the effects on quality of life (QoL) in MCI patients and their close others through biomarker-based dementia risk estimation are not well studied. Objective: The PreDADQoL project aims at providing empirical data on effects of such prediction on QoL and at developing an ethical and legal framework of biomarker-based dementia risk estimation in MCI. Methods: In the empirical study, 100 MCI-patients and their close others will be recruited from two sites (Germany and Spain). They receive standardized counselling on cerebrospinal fluid (CSF) biomarker-based prediction of AD dementia and a risk disclosure based on their AD biomarker status. A mixed methods approach will be applied to assess outcomes. Results: The pilot-study yielded a specification of the research topics and newly developed questionnaires for the main assessment. Within this binational quantitative and qualitative study, data on attitudes and expectations toward AD risk prediction, QoL, risk communication, coping strategies, mental health, lifestyle changes, and healthcare resource utilization will be obtained. Together with the normative part of the project, an empirically informed ethical and legal framework for biomarker-based dementia risk estimation will be developed. Conclusion: The empirical research of the PreDADQoL study together with the ethical and legal considerations and implications will help to improve the process of counselling and risk disclosure and thereby positively affect QoL and health of MCI-patients and their close others in the context of biomarker-based dementia risk estimation.

A mixed-methods study of cultural beliefs about dementia and genetic testing among Mexicans and Mexican-Americans at-risk for autosomal dominant Alzheimer's disease

Trials to prevent autosomal dominantly inherited Alzheimer's disease (ADAD) are critical and timely. However, cultural beliefs about AD and genetic testing may preclude informed consent and participation, especially among racial/ethnic minorities. This mixed-methods study examines cultural beliefs about AD and genetic screening among at-risk populations of Mexican heritage. We surveyed 86 Mexican and 37 Mexican-American family members of patients with ADAD and interviewed 18 respondents in Mexico to explore perceptions and knowledge regarding AD and genetic testing. While most respondents understood that AD is inherited in their families, they also had limited understanding of the genetic mechanisms behind AD. Many believed that AD is a normal part of aging or that it is a mental illness caused by bad habits. However, beliefs that AD is caused by a curse or God's will were uncommon. The interviews demonstrated that very few at-risk respondents understood their own risk for harboring the mutation causing AD in their family. Once informed, most expressed a strong interest in genetic testing, largely motivated by the desire to be better prepared for the development of AD. Health professionals treating and investigators enrolling members from families with ADAD cannot assume that they fully understand the nature of the illness; therefore, providers should provide comprehensive information about ADAD and genetic testing.

NO-Dependent Akt Inactivation by S-Nitrosylation as a Possible Mechanism of STZ-Induced Neuronal Insulin Resistance

Sporadic Alzheimer's disease (sAD) is associated with energy metabolism deficiency and impairment of insulin receptor (IR) signaling in the brain. In this context, low doses of intracerebroventricular (icv) injection of streptozotocin (STZ) in rodents has been used as an experimental model of sAD which leads to an insulin-resistant brain state and neurodegeneration. However, the STZ effects on brain insulin signaling-related proteins it is not appropriately elucidated. The aim of this study was to evaluate the beginning and progression of alterations in the brain IR pathway of rats after 1, 3, 5, and 7 days of STZ injection and investigate intracellular signaling involved on STZ induced insulin resistance. We observed that STZ injection causes cognitive impairment in the animals, a temporal variation of the insulin signaling-related proteins and apoptosis cell death in the hippocampus. We also have shown that STZ causes insulin resistance and impairment on phosphoinositide 3-kinase (PI3K) activity in the Neuro-2a cells through protein kinase B (Akt) inactivation by S-nitrosylation, which could upregulate GSK3-β activity. STZ ability to cause an insulin-resistant neuron state involves NO production and ROS production which may play an important role in the mechanism linked to STZ-induced neurotoxicity. The icv injection of STZ model and STZ exposed Neuro-2a cells may be potential experimental models for assessing molecules related to the pathogenesis of sAD.

Normal-But-Low Serum Folate Levels and the Risks for Cognitive Impairment

OBJECTIVE

This study aimed to examine the association between normal-but-low folate levels and cognitive function in the elderly population using a prospective cohort study.

METHODS

We analyzed 3,910 participants whose serum folate levels were within the normal reference range (1.5-16.9 ng/mL) at baseline evaluation in the population-based prospective cohort study named the "Korean Longitudinal Study on Cognitive Aging and Dementia." The association between baseline folate quartile categories and baseline cognitive disorders [mild cognitive impairment (MCI) or dementia] was examined using binary logistic regression analysis adjusting for confounding variables. The risks of incident MCI and dementia associated with the decline of serum folate level during a 4-year follow-up period were examined using multinomial logistic regression analysis.

RESULTS

The lowest quartile group of serum folate (≥1.5, ≤5.9 ng/mL) showed a higher risk of cognitive disorders than did the highest quartile group at baseline evaluation (odds ratio 1.314, p=0.012). Over the 4 years of follow-up, the risk of incident dementia was 2.364 times higher among subjects whose serum folate levels declined from the 2nd-4th quartile group to the 1st quartile than among those for whom it did not (p=0.031).

CONCLUSION

Normal-but-low serum folate levels were associated with the risk of cognitive disorders in the elderly population, and a decline to normal-but-low serum folate levels was associated with incident dementia. Maintaining serum folate concentration above 5.9 ng/mL may be beneficial for cognitive status.

Personalized risk for clinical progression in cognitively normal subjects-the ABIDE project

Background

Biomarkers such as cerebrospinal fluid (CSF) and magnetic resonance imaging (MRI) have predictive value for progression to dementia in patients with mild cognitive impairment (MCI). The pre-dementia stage takes far longer, and the interpretation of biomarker findings is particular relevant for individuals who present at a memory clinic, but are deemed cognitively normal. The objective of the current study is to construct biomarker-based prognostic models for personalized risk of clinical progression in cognitively normal individuals presenting at a memory clinic.

Methods

We included 481 individuals with subjective cognitive decline (SCD) from the Amsterdam Dementia Cohort. Prognostic models were developed by Cox regression with patient characteristics, MRI, and/or CSF biomarkers to predict clinical progression to MCI or dementia. We estimated 5- and 3-year individualized risks based on patient-specific values. External validation was performed on Alzheimer’s Disease Neuroimaging Initiative (ADNI) and an European dataset.

Results

Based on demographics only (Harrell’s C = 0.70), 5- and 3-year progression risks varied from 6% [3–11] and 4% [2–8] (age 55, MMSE 30) to 38% [29–49] and 28% [21–37] (age 70, MMSE 27). Normal CSF biomarkers strongly decreased progression probabilities (Harrell’s C = 0.82). By contrast, abnormal CSF markedly increased risk (5 years, 96% [56–100]; 3 years, 89% [44–99]). The CSF model could reclassify 58% of the individuals with an “intermediate” risk (35–65%) based on the demographic model. MRI measures were not retained in the models.

Conclusion

The current study takes the first steps in a personalized approach for cognitively normal individuals by providing biomarker-based prognostic models.

Electronic supplementary material

The online version of this article (10.1186/s13195-019-0487-y) contains supplementary material, which is available to authorized users.

From information to follow-up: Ethical recommendations to facilitate the disclosure of amyloid PET scan results in a research setting

In the field of Alzheimer's disease research, the use of biomarkers such as amyloid positron emission tomography (PET) has become widespread over a relatively brief period of time. There is an increasing tendency in research studies and trials to switch from no disclosure under any condition toward a qualified disclosure of individual research results, such as amyloid PET scan results. This perspective article aims to evaluate the possible need for a modification of the available recommendations on amyloid PET scan disclosure, based on recent empirical evidence obtained within the field of amyloid PET. This article also applies the International Guideline for Good Clinical Practice to the field of amyloid PET disclosure. Hence, we propose several recommendations to facilitate amyloid PET disclosure while minimizing possible risks of amyloid disclosure in a research context.

Perspectives on Communicating Biomarker-Based Assessments of Alzheimer's Disease to Cognitively Healthy Individuals

In clinical trials which target pathophysiological mechanisms associated with Alzheimer's disease, research participants who are recruited based on biomarker test results should be informed about their increased risk of developing Alzheimer's dementia. This paper presents the results of a qualitative focus group study of attitudes and concerns toward learning information about biomarker-based risk status among healthy research participants in the United Kingdom and Spain and people with dementia and their supporters/caregivers from countries represented in the European Working Group of People with Dementia of Alzheimer Europe. The study identified expectations related to learning risk status and preferences related to the content, quality, and follow-up of the disclosure process. The latter emphasize distinctions between risk and diagnoses, the importance of clear information about risk, and suggestions for risk reduction, as well as expectations for follow up and support. The implications of these preferences for practice are discussed. Providing details of research participants' experience and views may serve as a guide for the development of processes for the responsible disclosure of Alzheimer's disease biomarkers.

Amnestic MCI patients' experiences after disclosure of their amyloid PET result in a research context

BACKGROUND

Biomarkers such as amyloid imaging are increasingly used for diagnosis in the early stages of Alzheimer's disease. Very few studies have examined this from the perspective of the patient. To date, there is only limited evidence about how patients experience and value disclosure in an early disease stage.

METHODS

Semistructured interviews were carried out with 38 patients with amnestic mild cognitive impairment as part of an investigator-driven diagnostic trial (EudraCT, 2013-004671-12; registered on 20 June 2014) in which participants could opt to know the binary outcome (positive/negative) result of their amyloid positron emission tomography (PET) scan. Verbatim transcripts of the interviews were evaluated using qualitative content analysis and NVivo 11 software.

RESULTS

Eight of 38 patients received a positive amyloid PET scan result, and the remaining 30 patients received a negative amyloid PET scan result. After disclosure of the result to the patients, we interviewed each patient twice: 2 weeks after disclosure and 6 months after disclosure. Patients had difficulties in repeating the exact words used during disclosure of their amyloid PET scan result by the neurologist; yet, they could recall the core message of the result in their own words. Some patients were confused by the terminology of an amyloid-positive/negative test result. At 6 months, two of eight patients with a positive amyloid PET scan result experienced emotional difficulties (sadness, feeling worried). Three of 30 patients with a negative amyloid PET scan result started to doubt whether they had received the correct result. Patients reported that they experienced advantages after the disclosure, such as information about their health status, the possibility of making practical arrangements, medication, enjoying life more, and a positive impact on relationships. They also reported disadvantages following disclosure, such as having emotional difficulties, feeling worried about when their symptoms might worsen, the risk of a more patronizing attitude by relatives, and the possibility of a wrong diagnosis.

CONCLUSIONS

This exploratory study shows that the majority of patients can accurately recall the information received during disclosure. The experienced advantages and disadvantages reported by our patients depended on the outcome of the result (positive or negative) and the interval of the conducted interview (2 weeks or 6 months after amyloid PET disclosure). Discrepancies were found between patients' expectations according to the interview prior to amyloid PET disclosure (Vanderschaeghe et al. [Neuroethics. 2017;10:281-97]) and their actual experiences after their amyloid PET disclosure.

Kinetics and Molecular Docking Studies of 6-Formyl Umbelliferone Isolated from Angelica decursiva as an Inhibitor of Cholinesterase and BACE1

Coumarins, which have low toxicity, are present in some natural foods, and are used in various herbal remedies, have attracted interest in recent years because of their potential medicinal properties. In this study, we report the isolation of two natural coumarins, namely umbelliferone (1) and 6-formyl umbelliferone (2), from Angelica decursiva, and the synthesis of 8-formyl umbelliferone (3) from 1. We investigated the anti-Alzheimer disease (anti-AD) potential of these coumarins by assessing their ability to inhibit acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-site amyloid precursor protein (APP) cleaving enzyme 1 (BACE1). Among these coumarins, 2 exhibited poor inhibitory activity against AChE and BChE, and modest activity against BACE1. Structure–activity relationship analysis showed that 2 has an aldehyde group at the C-6 position, and exhibited strong anti-AD activity, whereas the presence or absence of an aldehyde group at the C-8 position reduced the anti-AD activity of 3 and 1, respectively. In addition, 2 exhibited concentration-dependent inhibition of peroxynitrite-mediated protein tyrosine nitration. A kinetic study revealed that 2 and 3 non-competitively inhibited BACE1. To confirm enzyme inhibition, we predicted the 3D structures of AChE and BACE1, and used AutoDock 4.2 to simulate binding of coumarins to these enzymes. The blind docking studies demonstrated that these molecules could interact with both the catalytic active sites and peripheral anionic sites of AChE and BACE1. Together, our results indicate that 2 has an interesting inhibitory activity in vitro, and can be used in further studies to develop therapeutic modalities for the treatment of AD.

Public beliefs and knowledge about risk and protective factors for Alzheimer's disease

BACKGROUND

The purpose of this study was to assess public beliefs and knowledge about risk and protective factors for Alzheimer's disease (AD).

METHODS

A brief survey module was added to the Health and Retirement Study, a longstanding national panel study of the U.S. population over the age of 50.

RESULTS

Respondents were 1641 adults (mean age=64.4 years, 53.6% female, 81.7% White). Most (60.1%) indicated interest in learning their AD risk, with 29.4% expressing active worry. Many failed to recognize that medications to prevent AD are not available (39.1%) or that having an affected first-degree relative is associated with increased disease risk (32%). Many respondents believed that various actions (e.g., mental activity, eating a healthy diet) would be effective in reducing AD risk.

CONCLUSION

Older and middle-aged adults are interested in their AD risk status and believe that steps can be taken to reduce disease risk. Tailored education efforts are needed to address potential misconceptions about risk and protective factors.

Diabetes mellitus and the risk of Alzheimer's disease: a nationwide population-based study

OBJECTIVES

Possible association between diabetes mellitus (DM) and Alzheimer's disease (AD) has been controversial. This study used a nationwide population-based dataset to investigate the relationship between DM and subsequent AD incidence.

METHODS

Data were collected from Taiwan's National Health Insurance Research Database, which released a cohort dataset of 1,000,000 randomly sampled people and confirmed it to be representative of the Taiwanese population. We identified 71,433 patients newly diagnosed with diabetes (age 58.74 ± 14.02 years) since January 1997. Using propensity score, we matched them with 71,311 non-diabetic subjects by time of enrollment, age, gender, hypertension, hyperlipidemia, and previous stroke history. All the patients were followed up to December 31, 2007. The endpoint of the study was occurrence of AD.

RESULTS

Over a maximum 11 years of follow-up, diabetic patients experienced a higher incidence of AD than non-diabetic subjects (0.48% vs. 0.37%, p<0.001). After Cox proportional hazard regression model analysis, DM (hazard ratio [HR], 1.76; 95% confidence interval [CI], 1.50-2.07, p<0.001), age (HR, 1.11; 95% CI, 1.10-1.12, p<0.001), female gender (HR, 1.24; 95% CI, 1.06-1.46, p=0.008), hypertension (HR, 1.30; 95% CI, 1.07-1.59, p=0.01), previous stroke history (HR, 1.79; 95% CI, 1.28-2.50, p<0.001), and urbanization status (metropolis, HR, 1.32; 95% CI, 1.07-1.63, p=0.009) were independently associated with the increased risk of AD. Neither monotherapy nor combination therapy with oral antidiabetic medications were associated with the risk of AD after adjusting for underlying risk factors and the duration of DM since diagnosis. However, combination therapy with insulin was found to be associated with greater risk of AD (HR, 2.17; 95% CI, 1.04-4.52, p=0.039).

CONCLUSION

Newly diagnosed DM was associated with increased risk of AD. Use of hypoglycemic agents did not ameliorate the risk.

A review of quality of life after predictive testing for and earlier identification of neurodegenerative diseases

The past decade has witnessed an explosion of evidence suggesting that many neurodegenerative diseases can be detected years, if not decades, earlier than previously thought. To date, these scientific advances have not provoked any parallel translational or clinical improvements. There is an urgency to capitalize on this momentum so earlier detection of disease can be more readily translated into improved health-related quality of life for families at risk for, or suffering with, neurodegenerative diseases. In this review, we discuss health-related quality of life (HRQOL) measurement in neurodegenerative diseases and the importance of these "patient reported outcomes" for all clinical research. Next, we address HRQOL following early identification or predictive genetic testing in some neurodegenerative diseases: Huntington disease, Alzheimer's disease, Parkinson's disease, Dementia with Lewy bodies, frontotemporal dementia, amyotrophic lateral sclerosis, prion diseases, hereditary ataxias, Dentatorubral-pallidoluysian atrophy and Wilson's disease. After a brief report of available direct-to-consumer genetic tests, we address the juxtaposition of earlier disease identification with assumed reluctance toward predictive genetic testing. Forty-one studies examining health-related outcomes following predictive genetic testing for neurodegenerative disease suggested that (a) extreme or catastrophic outcomes are rare; (b) consequences commonly include transiently increased anxiety and/or depression; (c) most participants report no regret; (d) many persons report extensive benefits to receiving genetic information; and (e) stigmatization and discrimination for genetic diseases are poorly understood and policy and laws are needed. Caution is appropriate for earlier identification of neurodegenerative diseases but findings suggest further progress is safe, feasible and likely to advance clinical care.

Amyloid imaging, risk disclosure and Alzheimer's disease: ethical and practical issues

PET ligands that bind with high specificity to amyloid plaques represent a major breakthrough in Alzheimer's disease (AD) research. Amyloid neuroimaging is now approved by the US FDA to aid in the diagnosis of AD, and is being used to identify amyloid-positive but asymptomatic individuals for secondary AD prevention trials. The use of amyloid neuroimaging in preclinical populations raises important ethical and practical challenges, including determining appropriate uses of this technology, evaluating the potential benefits and harms of disclosing results, and communicating effectively about testing with patients and family members. Emerging policy issues also require consideration (e.g., legal safeguards for biomarker-positive individuals). Further research is needed to inform effective and ethical implementation and regulation of amyloid imaging.

Amyloid imaging in cognitively normal individuals, at-risk populations and preclinical Alzheimer's disease

Recent developments of PET amyloid ligands have made it possible to visualize the presence of Aβ deposition in the brain of living participants and to assess the consequences especially in individuals with no objective sign of cognitive deficits. The present review will focus on amyloid imaging in cognitively normal elderly, asymptomatic at-risk populations, and individuals with subjective cognitive decline. It will cover the prevalence of amyloid-positive cases amongst cognitively normal elderly, the influence of risk factors for AD, the relationships to cognition, atrophy and prognosis, longitudinal amyloid imaging and ethical aspects related to amyloid imaging in cognitively normal individuals. Almost ten years of research have led to a few consensual and relatively consistent findings: some cognitively normal elderly have Aβ deposition in their brain, the prevalence of amyloid-positive cases increases in at-risk populations, the prognosis for these individuals is worse than for those with no Aβ deposition, and significant increase in Aβ deposition over time is detectable in cognitively normal elderly. More inconsistent findings are still under debate; these include the relationship between Aβ deposition and cognition and brain volume, the sequence and cause-to-effect relations between the different AD biomarkers, and the individual outcome associated with an amyloid positive versus negative scan. Preclinical amyloid imaging also raises important ethical issues. While amyloid imaging is definitely useful to understand the role of Aβ in early stages, to define at-risk populations for research or for clinical trial, and to assess the effects of anti-amyloid treatments, we are not ready yet to translate research results into clinical practice and policy. More researches are needed to determine which information to disclose from an individual amyloid imaging scan, the way of disclosing such information and the impact on individuals and on society.

Impact of genetic risk assessment on nutrition-related lifestyle behaviours

Genetic susceptibility testing for common complex disease is a practice that is currently in clinical use. There are two types of gene mutations, and therefore, two varieties of genotype testing: deterministic and susceptibility. As the term suggests, deterministic genes determine whether or not a person will develop a given trait in mendelian fashion, such as Huntington's disease. Genotype screening for such deterministic mutations has existed for decades, and is commonly used in routine medical practice. In recent years, the sequencing of the human genome has identified several 'susceptibility genes' or genes with incomplete penetrance. Mutations in these genes may increase disease susceptibility, but are not causative for disease. Genetic susceptibility testing allows unaffected individuals to obtain risk information for a variety of common complex diseases and health conditions including Alzheimer's disease (AD), CVD, cancer and diabetes. The availability of genetic susceptibility testing has increased over the past decade, and several studies are now focusing on the impact that genetic testing has on health and other lifestyle behaviours related to nutrition. The aim of this paper is to review the literature and evaluate what, if any, impact genetic risk assessment has on behaviours related to nutrition and physical activity. This paper summarises seven clinical studies that evaluated the impact of disclosing genetic risk information for disease on nutrition-related health behaviour changes. Of these seven studies, only three studies reported that health behaviour change was influenced by genotype disclosure.

Differences between African American and White research volunteers in their attitudes, beliefs and knowledge regarding genetic testing for Alzheimer's disease

Genetic susceptibility testing for common diseases is expanding, but little is known about race group differences in test perceptions. The purpose of this study was to examine differences between African Americans and Whites in knowledge, attitudes, and motivations regarding genetic susceptibility testing for Alzheimer's disease (AD). Before enrolling in an AD genetic testing research trial, 313 first-degree relatives of AD patients (20% African American; 71% female; mean age = 58 years) were surveyed regarding: (1) knowledge about genetics and AD risk; (2) concerns about developing AD; and (3) reasons for seeking testing. In comparison to Whites, African Americans were less knowledgeable about genetics and AD risk (p < .01) and less concerned about developing AD (p < .05), with lower levels of perceived disease risk (p = .04). The results suggest that African Americans and Whites differ notably in their knowledge, beliefs, and attitudes regarding genetic testing for AD. Additional research with more representative samples is needed to better understand these differences.