MEMP PhD Thesis Defense: Jordan Harrod

Impact of Sleep-Related Factors in Alzheimer’s Disease

Sleep-related factors such as sleep apnea and sedative medications have been linked to Alzheimer's disease risk in large observational studies, but these associations may be confounded by a structural problem: Alzheimer's disease is a clinical diagnosis, and any exposure that changes a person's contact with the healthcare system can appear to influence dementia risk regardless of whether a biological relationship exists. This dissertation uses longitudinal data from the National Alzheimer's Coordinating Center and electronic health records from Mass General Brigham to investigate how healthcare utilization and clinical infrastructure shape observed associations between sleep-related exposures and AD diagnosis. In the NACC cohort, we find that the apparent protective effect of sleep apnea depends on whether we measure lifetime diagnostic patterns or time-varying exposure, and that the identity of the person reporting a patient's symptoms moderates key risk associations. In the MGB cohort, we use a target trial emulation framework to show that the protective association between benzodiazepines and AD diagnosis attenuates substantially after adjusting for healthcare utilization, with primary care access and prescriber specialty emerging as important structural confounders. Collectively, these findings demonstrate that the clinical infrastructure through which we observe dementia systematically shapes the associations we find, with implications for any observational study in which the outcome is a clinical diagnosis and the exposure is correlated with healthcare engagement.

Thesis Supervisors:
Emery N. Brown, PhD, MD
Edward Hood Taplin Professor of Computational Neuroscience, MIT
Warren M. Zapol Professor of Anesthesia, Harvard Medical School

Ed Boyden, PhD
Professor, Departments of Brain and Cognitive Sciences, Media Arts and Sciences, and Biological Engineering, MIT
Y. Eva Tan Professor in Neurotechnology, McGovern Institute and HHMI

Thesis Committee Chair:
Roy E. Welsch, PhD
Professor of Statistics and Data Science, MIT Sloan School of Management and the MIT Center for Statistics and Data Science
Professor of Management, Eastman Kodak Leaders for Global Operations
Director, MIT Center for Computational Research in Economics and Management Science

Thesis Readers:
Sudeshna Das, PhD
Associate Professor of Neurology, Massachusetts General Hospital and Harvard Medical School
Director, Massachusetts General Hospital Biomedical Informatics Core (BMIC) 

Stan N. Finkelstein, MD
Associate Professor of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School
Senior Research Scientist at the Institute for Data, Systems and Society at MIT

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Topic: Jordan Harrod MEMP PhD Thesis Defense
Time: Tuesday, April 28, 2026, 12:00 PM Eastern Time (US and Canada)

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