Venous thromboembolism is a major national health problem, especially among the elderly. While the incidence of pulmonary embolism has decreased over time, the incidence of deep vein thrombosis remains unchanged for men and is increasing for older women. These findings emphasize the need for more accurate identification of patients at risk for venous thromboembolism, as well as a safe and effective prophylaxis.

Hospital or nursing home confinement, surgery, trauma, malignant neoplasm, chemotherapy, neurologic disease with paresis, central venous catheter or pacemaker, varicose veins, and superficial vein thrombosis are independent and important risk factors for VTE.

The Rochester Epidemiology Project is a unique medical records-linkage system that encompasses the care delivered to residents of Rochester and Olmsted County, Minnesota. It is the creation of Dr. Leonard T. Kurland, who envisioned the population-based data resource that would result from combining the clinical documentation developed by the Mayo Clinic with that obtained by other community providers, most notably the Olmsted Medical Group and its affiliated Olmsted Community Hospital. Kurland built on the Mayo unit medical record system that was designed by Dr. Henry S. Plummer in 1907 and on the medical and surgical indexing systems introduced by Dr. Joseph Berkson in 1935. By affording access to details of the medical care given to local residents, the Rochester Epidemiology Project is able to provide accurate incidence data for almost any serious condition and to support population-based analytic studies of disease causes and outcomes. Thus, epidemiologic studies of a wide array of disorders have been possible and have culminated in almost 900 publications since the system was organized in 1966. Olmsted County is one of the few places in the world where the occurrence and natural history of diseases can be accurately described and analyzed in a defined population for a half century or more.

Among residents of Olmsted County, Minnesota, MGUS was found in 3.2 percent of persons 50 years of age or older and 5.3 percent of persons 70 years of age or older.

Venous thromboembolism recurs frequently, especially within the first 6 to 12 months, and continues to recur for at least 10 years after the initial VTE. Patients with VTE with neurologic disease and paresis or with malignant neoplasm are at increased risk for recurrence, while VTE patients with transient or reversible risk factors are at less risk.