Alzheimer's disease and Down syndrome
Carnero-Pardo, C. Thematic interview with Dr. Juan Fortea: Alzheimer's disease in Down syndrome [online]. Circunvalación del Hipocampo, February 2019 Dr. Juan Fortea, neurologist, is director of the Alzheimer-Down Unit of the Hospital de la Santa Creu i Sant Pau in Barcelona and the Catalan Down Syndrome Foundation, program director of the Professional Interest Area (PIA, Area of Interest Professional) in Down syndrome of the Alzheimer's Association and, currently, Coordinator of the Study Group of Behavioral Neurology and Dementias of the Spanish Neurology Society (SEN).
Despite his youth, he has extensive research experience, has received multiple awards and distinctions, and is one of the current world leaders in Alzheimer's disease in patients with Down syndrome.
Why an Alzheimer-Down Unit?
Dr. Fortea: Down syndrome (DS) is strongly associated with Alzheimer's disease (AD). This relationship has a genetic basis, DS is a trisomy of chromosome 21. Triplication of the amyloid precursor protein gene, which in the general population is associated with autosomal dominant AD, is a sufficient and necessary cause for AD in DS . Therefore, the cumulative incidence is more than 80-90% in the seventh decade of life. AD is, without a doubt, the main health problem and cause of death in people with DS. This very high risk had gone unnoticed in the past due to the low life expectancy that people with DS had until the end of the 20th century. Today, however, their life expectancy in developed countries exceeds 60 years. On the other hand, the diagnosis of AD in the context of the intellectual disability associated with DS is not easy, so a certain specialization is required.
What is the main mission of the Alzheimer-Down Unit?
Dr. Fortea: The main mission of the Alzheimer-Down Unit, created between the Hospital de la Santa Creu i Sant Pau and the Catalan Down Syndrome Foundation, is the development and implementation of a health plan aimed at active population screening of the EA in the SD. We are the reference center for neurological pathology associated with DS in all of Catalonia. This is a pioneering program worldwide by which we offer a comprehensive neurological and neuropsychological evaluation for the early detection and treatment of AD (and other neurological problems).
Interviewer: You are the principal investigator of the Down-Alzheimer Barcelona Neuroimaging Initiative project (DABNI project). What does it consist of and what are its objectives? Do you already have some results?
Dr. Fortea: The DABNI project is a research program focused on the pathophysiology and natural history of AD in DS that is enrolled in the health plan. All the people cared for have the opportunity to participate in an intensive biomarker program that includes from a plasma extraction, cerebrospinal fluid, acquisition of magnetic resonance and positron emission tomography with different tracers (glucose, amyloid and tau), to electroencephalograms and sleep tests. Obviously not all people take all the tests but they choose which ones they want to participate in.
As a result, we have the largest cohort in the world with a multimodal biomarker evaluation thanks to which we have been able to demonstrate, for the first time, the usefulness of a plasma biomarker, neurofilament light chain levels, for the diagnosis of the EA in the SD. I highlight this study because, as I pointed out, the diagnosis of AD in DS is complex, and having a biomarker in plasma can change routine clinical practice.
Interviewer: In the DABNI study, patients' sleep is systematically studied. How important is sleep in the development of AD? Is this relevance specific and unique for patients with DS?
Dr. Fortea: Sleep is one of the most current topics in AD, since it is during sleep that the brain clearance of amyloid occurs mainly (among others). Increasingly strong evidence shows that sleep disturbances, especially sleep apneas, are associated with an increased risk of AD. DS is associated, on the one hand, with increased amyloid production and, on the other, with a very high prevalence of sleep apnea. Therefore, although we lack data, everything seems to point to a singular relevance of this association in DS.
There are currently several clinical trials in progress in asymptomatic patients with a high genetic risk of suffering from AD. Would a similar study in patients with DS make sense? Dr. Fortea: Of course. A study in people with DS would even present several advantages over those developed in autosomal dominant Alzheimer's. From a conceptual point of view, it could even be a better biological model in the sense that in DS there is an overproduction of amyloid (due to excess genetic load), while in family forms there is a greater proportion of more forms. long peptides that have a greater propensity for aggregation. From a practical point of view, the number of people with DS is several orders of magnitude higher than that of people carrying mutations, there are many more people with DS in Spain than carriers diagnosed worldwide. Indeed, there are other difficulties derived from the complexity of DS, such as intellectual disability that entails difficulties in evaluation and ethical considerations in relation to consent, as well as the frequent presence of associated medical comorbidities. However, the worst of all is nihilism and so-called protection. Doing research on people with DS is the only way to improve their quality of life and get treatment, and exclude them from research with the intention of protecting them, a new form of discrimination. I can assure you, in any case, that the interest on the part of the pharmaceutical industry exists and I am optimistic about the possibility of an upcoming clinical trial in people with DS.
Interviewer: As Coordinator of the SEN's Behavioral Neurology and Dementia Study Group, how do you see the situation of clinical care and research on dementia in our country? What do you think would be the most immediate needs and challenges?
Dr. Fortea: My assessment is ambivalent. We have very good professionals dedicated to dementia, but unfortunately there are still few. Even more serious is the fact that clinical care for dementias is extraordinarily heterogeneous in our country. There is a high degree of inequity in care, even within the same city, depending on the center or specialist that is attended. The care of a person with cognitive problems is approached from different specialties, in few cases in memory units with multidisciplinary teams, and even more infrequently, with access to biomarkers or clinical trials. The research situation, especially the clinical one, is also precarious, with neurologists with great talent and enthusiasm, but with care overload and in a context of serious underfunding.
We have our hopes in the announced National Alzheimer's Plan, which, although it arrives late in our country, I hope is a mechanism to alleviate some of these deficiencies. From the board, for our part, we want to promote collaborations between national researchers and, above all, promote the vocation in this field of young neurologists.