Dr. Jacobsen is a chronic disease epidemiologist with a primary interest in prostate diseases, both benign and malignant. He serves as Principal Investigator (along with Dr. Michael Lieber in the Department of Urology) of the Olmsted County Study of Urinary Symptoms and Health Status among Men, a prospective cohort study of lower urinary tract symptoms and surrogate markers for benign prostatic hyperplasia that is in its fifteenth year of followup.

He is also Principal Investigator of the Rochester Epidemiology Project, the infrastructure grant that links medical information from all providers of medical care to residents of Olmsted County, Minnesota residents. This infrastructure supports the hundreds of population-based investigations under way in Olmsted County.

He has recently focused additional efforts on research integrity, including an active extramurally-funded research program, teaching the course on Responsible Conduct of Research and building new clinical research tools to aid investigators in carrying out their research using best practices. He also is an active collaborator in population-based studies of coronary heart disease, left ventricular dysfunction, developmental disorders and vaccine research.