Electronic health records (EHRs) are nevertheless used as investigational tools in epidemiology, despite its original clinical intent. Uses include cross-sectional studies in individual hospitals and geographical longitudinal studies. Explored herein is EHR use in a wide-scale health research. They are then measured up to conventional epidemiologic techniques. Also tackled is research strengthening with large samples, along with EHR-resultant patient generalizability. It was found that EHR-based studies, although less reliable, tended to cheaper and faster than conventional methods. Population-wide health and clinical practices could progress if new technologies combine with EHR epidemiology. Improved collections of vital records and behavioral measures are also needed to reinforce EHR-based studies.