Create population-health.md for research documentation

Added a new document on population health imaging, outlining key interests and research areas.

Author: vishwaparekh

research/population-health.md

@@ -0,0 +1,16 @@
+---
+layout: default
+title: Population Health
+---
+
+## Population Health Imaging
+
+We leverage large-scale, clinically acquired imaging datasets to study health at the population level.
+
+Our interests include:
+
+- **Opportunistic screening** – extracting hidden risk signals (e.g., future dementia or cardiometabolic risk) from scans obtained for other reasons.
+- **Disparities and access** – understanding how imaging findings and AI models interact with sociodemographic factors.
+- **Longitudinal cohorts** – linking imaging, clinical data, and outcomes to uncover trajectories of health and disease across populations.
+
+This work complements our disease modeling efforts by asking questions at the scale of cohorts and health systems.