Relative impact of risk factors for deep vein thrombosis and pulmonary embolism: a population-based study

To assess the potential impact of controlling risk factors on the incidence of venous thromboembolism by estimating the population attributable risk (defined as the percentage of all cases of a disease in a population that can be "attributed" to a risk factor) for deep vein thrombosis and pulmonary embolism associated with venous thromboembolism risk factors.

Using data from a population-based, nested, case-control study of the 625 Olmsted County, Minnesota, residents with a definite first lifetime deep vein thrombosis or pulmonary embolism diagnosed during the 15-year period 1976 to 1990 and 625 unaffected Olmsted County residents matched for age and sex, we developed a conditional logistic regression model appropriate to the matched case-control study design and then estimated attributable risk for the risk factors individually and collectively.

Fifty-nine percent of the cases of venous thromboembolism in the community could be attributed to institutionalization (current or recent hospitalization or nursing home residence). Hospitalization for surgery (24%) and for medical illness (22%) accounted for a similar proportion of the cases, while nursing home residence accounted for 13%. The individual attributable risk estimates for malignant neoplasm, trauma, congestive heart failure, central venous catheter or pacemaker placement, neurological disease with extremity paresis, and superficial vein thrombosis were 18%, 12%, 10%, 9%, 7%, and 5%, respectively. Together, the 8 risk factors accounted for 74% of disease occurrence.

Factors associated with institutionalization independently account for more than 50% of all cases of venous thromboembolism in the community. Greater emphasis should be placed on prophylaxis for hospitalized medical patients. Other recognized risk factors account for about 25% of all cases of venous thromboembolism, while the remaining 25% of cases are idiopathic.