Mayo Clinic, Olmsted County, US

Description of unit/research group

Division of Rheumatology, Department of Internal Medicine, Mayo Clinic, Rochester, MN, USA: Ranked consistently among the top 5 centers in the US for the treatment of rheumatic disease by US News and World Report, the Division of Rheumatology has been a leader in clinical practice and research at Mayo Clinic since the time of Dr. Philip S. Hench, who shared the Nobel Prize for Medicine in 1950 for the discovery and use of cortisone in the treatment of rheumatoid arthritis (RA). Clinical activities, which include approximately 30,000 inpatient and outpatient visits per year, are conducted by 20 full-time consultants, 13 secretaries, 8 clinical assistants, 4 nurses, and 3 mid-level providers. Physicians care for patients with RA, psoriatic arthritis, ankylosing spondylitis, and crystalline arthritis, among others.

Rheumatology Research Study Unit (RSU):The RSU has 4 full-time study coordinators. Currently, the RSU is successfully managing over 40 therapeutic and non-therapeutic clinical studies. The study coordinators have training and certification in requisite policies/procedures, including Good Clinical Practice (GCP), research ethics, study file documentation & management, informed consent, confidentiality & privacy, data security & integrity, and use of biological specimens.

Department of Health Sciences Research. The department contains 3 divisions: Epidemiology, Biomedical Statistics & Informatics, and Health Care Policy & Research. Large-scale, ongoing and highly successful epidemiologic studies of the population of Olmsted County, Minnesota, and referral bias studies which encompass the Mayo Clinic referral practice are hallmarks of the Department’s epidemiological efforts. These activities employ 7 physician-epidemiologists, and 10 PhD epidemiologists and others including visiting scientists, graduate students and clinical fellows. The Biomedical Statistics and Informatics division comprises more than 200 members, who provide integrated collaborative research support in both biostatistics and biomedical informatics. The division has provided consultation on statistical design and analysis for the staff at Mayo Clinic since this service was introduced by Joseph Berkson (known for the Berkson’s Bias) in 1932.


The Rochester Epidemiology Project (REP). Studies that collect longitudinal population-based medical data are rare in the US. Most available population-based data from the US are cross-sectional or focus on select age groups, economic groups, a specific disease, or insurance status. In contrast, the Rochester Epidemiology Project (REP Web site: provides longitudinal data for the complete population residing in a well-defined geographic region. The REP has been continuously funded since 1966 and is possible through a confluence of several unique circumstances. First, the population is relatively isolated geographically; Olmsted County is 80 miles from any other urban center. Second, almost all medical care is delivered by Mayo Clinic or Olmsted Medical Center or their affiliated hospitals. Third, all providers use comprehensive medical records that include all information, regardless of setting (e.g., inpatient, outpatient, emergency department, satellite clinic). Fourth, indexing of medical diagnoses and surgical procedures is routinely conducted for research purposes. Fifth, community health care providers are willing to share data for research purposes. In this setting, the REP is able to capture all inpatient and outpatient medical records from all sources of medical care available to and used by members of this geographically defined population. Each medical care site that participates in the REP also solicits and documents permission from individual patients for their records to be used in research studies. Currently, 95% of patients have granted permission for their records to be used in research. In 2008, the REP contained 1,145,856 patient records from 49 different health care providers that matched to 486,564 individuals who had been a resident of Olmsted County at some point between 1966 and 2008.