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Epidemiology Informs Randomized Clinical Trials of Cognitive Impairments Neuromedicine and Late-Onset, Sporadic Dementias Gustafson DR. Epidemiology Informs Randomized Clinical Trials of Cognitive Impairments Neuromedicine and Late-Onset, Sporadic Dementias. J Neurol Neuromedicine (2018) 3(5): 13-18 www.jneurology.com www.jneurology.com Journal of Neurology && NeuromedicineNeuromedicine Opinion Article Open Access Epidemiology Informs Randomized Clinical Trials of Cognitive Impairments and Late-Onset, Sporadic Dementias Deborah R. Gustafson1,2* 1Department of Neurology, State University of New York, Downstate Medical Center, New York, USA 2Department of Health and Education, University of Skövde, Sweden Despite strong and consistent evidence1, criticisms of the association Article Info between vascular factors and cognitive impairments (CI) and late-onset, Article Notes sporadic dementias (LOD), abound. A common critique is, “If vascular Received: September 05, 2018 Accepted: September 18, 2018 clinical trials of treatments for vascular risk fail to improve cognition or *Correspondence: preventrisk factors LOD?’ identified Concerns in regarding observational shortfalls epidemiology in statistical are power, real, rigorous why do Dr. Deborah R. Gustafson, MS, PhD, Professor, Department of Neurology, Section for Neuroepidemiology, State University of New York, Downstate Medical Center, Box 1213, 450 Clarkson outcome measurements, replication, and translational application, Ave., Brooklyn, NY 11203, USA; Telephone No: 718-270-1581; analyses, adjustment for multiple comparisons, precise exposure and Fax No: 718-221-5761; E-mail: [email protected].. along with relatively low-risk estimates, flood the field. Despite this, © 2018 Gustafson DR. This article is distributed under the terms debatestimulating and platformsscientific, forinnovative, biomarker critical, development and controversial have been pointsunveiled. of of the Creative Commons Attribution 4.0 International License view persist because of observational epidemiology. Many forums for The scientific community should not cast a bleak view of the vascular Keywords: acknowledgmentfactor, LOD, life course,of these and concerns aging epidemiologyprovides a natural research segue landscape for the Dementia as what is too often portrayed and conveyed. From one vantage point, Epidemiology Randomized clinical trials Observational scientific community to focus on, facilitate and feed forward future solutions and fill knowledge gaps. population-level questions and solutions, how can there be a better translationGiven the to strengthsRandomized of ControlledDementia EpidemiologyTrials (RCT) andin identifying precision medicine approaches? First and foremost, is an acknowledgment controlthat Epidemiology, it. Other challenges not RCT, include more recognizingaccurately reflectsthat: 1) ‘realCI and world’. LOD The epidemiology embraces the variability, while an RCT seeks to result from exposures occurring over the life course; 2) definitions and terminology related to exposures and clinical outcomes are inconsistent; 3) characteristics of populations at risk vary; 4) mid-life, medicationlate-life associations adherence) are required difficult toto mimicachieve in desired RCT; 5) effectsthere are observed a paucity in of data on late life exposures and flux; 6) duration of exposure(s) (e.g., the observational epidemiology is ignored in most RCTs; 7) RCTs do not acknowledge and/or address reverse causality; and finally, typically moreignored of arethe 8)chaos phenotypic (intra- and cha inter-individualnges with aging; variabilities) 9) birth cohort; to better 10) multimorbidities; and 11) genetic susceptibility. RCT must embrace identifyA theme prevention among strategies the aforementioned that work (See challenges Tables 1 is and that 2). life course epidemiology consistently points to the importance of timing (See Figure 1). Early-, mid- and late-life exposures in association with CI and LOD differ depending on when an exposure is measured and the length of time between exposure measurement and clinical disease onset. Page 13 of 18 Gustafson DR. Epidemiology Informs Randomized Clinical Trials of Cognitive Impairments Journal of Neurology & Neuromedicine and Late-Onset, Sporadic Dementias. J Neurol Neuromedicine (2018) 3(5): 13-18 Table 1. Issues for Critically Evaluating the Epidemiology of Vascular multi-stage brain and peripheral processes as well as Exposures Associated with Cognitive Impairments and Late-Onset, Sporadic Dementias. When measured in mid-life, 1. Definition of the exposures higherthe influence levels ofof vascular evolving 15risk LOD-related factors are neuropathologies associated with 2. Definition of the outcomes: LOD, LOD subtype, CI higheron systemic LOD risk,‘exposures’ however, when measured in late-life, 3. Characteristics of the population at risk 4. Age of exposure or onset of outcome 5. Duration of exposure vascular factors may be protective due to the influence 6. Timing of exposure in relation to outcome of underlying LOD- or aging-related neuropathologies on 7. Survival time their expression. This is termed ‘reverse causality’ and is 8. Birth cohort andobserved blood incholesterol LOD association levels. In studies, addition, with discovered for example, in the 9. Study design body weight or body mass index (BMI), blood pressure 10. Analysis strategy 11. Competing risks 1990s, APOEε4 allele possession, encoding for a protein 12. Molecular epidemiology – genes and biomarkers on the surface of lipoproteins, and influencing. Other both vascular lipid metabolism and LOD risk is an example 16of the major role of vascular risk factors in LOD etiology toEarly educational life exposures attainment relate to developmental origins (in susceptibility genes potentially, ACE andmodifying blood pressure the effect18, and of utero and neonatal development)2,3 hypotheses, in addition vascular phenotypes in association17 with LOD include for . Mid-life exposures, typically . example, FTO and obesity 19 measured between age 35-60 years, are most evolved clusterin/APOJ and blood cholesterol for vascular (e.g., hypertension, overweight and obesity, hypercholesterolemia) and metabolic (e.g., Type 2 diabetes, Given this rich epidemiologic substrate, what are next Virus,adiposity, HIV) menopause) mechanisms; and burgeoning for steps to identify preventive agents for CI and LOD? The chronic infectious4,5 diseases (e.g., Human Immunodeficiency following example is one potential research question and . Late-life exposures, typically measured at studyA Practical design thatExample: translates The the Case epidemiology of Body Weightto the RCT. and age 65 years and older in agreement with the age criterion Cognitive Impairments declinesfor LOD, inare blood dynamic, pressure and reflect ageing-related changes, baselineusually decline levels thatin mid-life parallel6 vascularor precede risk cognitive factors,7-9 suchdecline. as and body weight from varying Numerous observational epidemiology studies report scores . In addition, are the presence of multimorbidities, on associations between adiposity (body weight, body mass This is10-13 underscored by comparing mid- versus late-life risk index, waist circumference, waist-to-hip20-22 ratio, adipokines) against a background of cognitive reserve . In total, this and CI or LOD (See Table 4) . Reverse 8,20causality and. balanced or not by compensatory or resilience14 factors effect modification by APOEε4 is evident . Metabolic21 consequences and correlates of declining cognitive dysregulation as measured via adipokines may inform functions.life course milieuIn late-life, influences the timing the manifestation of associations of functional between Alzheimer’sOverweight diseaseand obesity (AD), andare forprimary aging-related cardiovascular chronic risk factors. Pharmacologic interventions for CI and vascular exposures and outcome is critical due to potential vascular diseases such as Type 2 diabetes, hypertension, Table 2. Upgrade Overdue. Translating the Observational Late-Onset Dementia Epidemiology to Randomized Clinical Trials. Observational CI & Late-Onset, Sporadic Dementia Randomized Clinical Trials Epidemiology Prioritize intermediate phenotypes Intermediate phenotypes as primary or secondary outcomes Wisely select pooled or global replication analyses of existing Refine linkages data to refine linkages between exposure and outcome Stratify by gene variants relevant for pharmacokinetics, Employ gene stratification metabolic and vascular risk Embrace multi-morbidities (multiple exposures) Recruit on the basis of multi-morbidities Enhance analysis of polypharmacy Recruit on the basis of polypharmacy Trajectories of medication use across populations Chronicity of medication use Renew attention to medication adherence and management Incorporate adherence patterns in design and data on a global scale interpretation Define and consider global health disparities Actively include health disparities samples More industry partnerships to improve exposures Use better exposures with industry partners End result: Observational data linked more directly and efficiently with clinical trial implementation. Page 14 of 18 Gustafson DR. Epidemiology Informs Randomized Clinical Trials of Cognitive Impairments and Journal of Neurology & Neuromedicine Late-Onset, Sporadic Dementias. J Neurol Neuromedicine (2018) 3(5): 13-18 Figure 1. Better mid- and later life identification and characterization of populations at risk for CI and late-onset, sporadic dementias. Life course epidemiology points to the importance of timing. Mid- and late-life exposures
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