ADNI data is made available to researchers around the world. As such, there are many active research projects accessing and applying the shared ADNI data. To further encourage Alzheimer’s disease research collaboration, and to help prevent duplicate efforts, the list below shows the specific research focus of the active ADNI investigations. This information is requested annually as a requirement for data access.
|Principal Investigator's Name:||Wesley Thompson|
|Institution:||University of California, San Diego|
|Proposed Analysis:||ABSTRACT Context: The expression, type, and severity of psychiatric disorders vary substantially over the lifespan, as well as during critical periods of development or change such as early childhood, adolescence, and menopause. A developmental or lifespan approach to psychiatric disorders is integral to understanding the prodromal course of many illnesses and the factors that serve as significant risk factors for disease onset or worse outcomes. The standard experimental designs employed in the field of psychiatry are not always ideal for understanding longitudinal or developmental processes. In particular, cohort effects are often minimized or ignored. A long-known approach to designing such studies which has been only rarely used in psychiatry is the accelerated longitudinal design (ALD). The ALD is a structured multi-cohort longitudinal design (MLD) where subjects enter the study at selected ages (age cohorts) spanning the time period under investigation, with each subject followed longitudinally for a shorter time span relative to the entire time span of interest. Cohort effects are routinely considered in ALDs and can be tested formally, in contradistinction with cross-sectional and single cohort longitudinal designs, and with fewer assumptions and more power than in unstructured MLDs. Objective: To discuss experimental designs and the benefits of the ALD approach for assessing the genetic, biological, and environmental impacts on the development of psychiatric disorders across the lifespan or during critical periods of change. Data Sources: We first discuss the limitations of the usual designs for this purpose: structured and unstructured cross-sectional designs, the single-cohort longitudinal design, the unstructured multi-cohort longitudinal design; we then define the ALD. We discuss the assumptions underlying the ALD, the decisions to be made in proposing an ALD, analytic approaches to the ALD, and finally the benefits and challenges of the ALD approach for consideration of the developmental or lifespan evolution of psychiatric disorders. We apply the methods described to data taken from the Alzheimer's Disease Neuroimaging Initiative (ADNI) study to examine the genetic and environmental impacts on developmental trajectories of hippocampal volume in older adults and the importance of considering cohorts effects in the design and analysis of multi-cohort longitudinal studies. Conclusions: Establishing developmental, change or lifespan trajectories is crucial for a better understanding of mechanisms that influence psychiatric disorders. Risk factors can only be understood in the context of the stage of the lifespan they are acting in. This requires longitudinal data acquired over long time periods that usually cannot be covered using single cohort designs. Unstructured multi-cohort longitudinal designs (e.g., ADNI) are commonly employed alternatives in psychiatric research. We argue that cohort effects must be carefully considered in such designs and propose that structured multi-cohort longitudinal designs, in particular the ALD, represent a particularly viable and valuable alternative for developmental studies psychiatric disorders.|