Summary
Reasons for trends in venous thromboembolism (VTE) incidence are uncertain. It was
our objective to determine VTE incidence trends and risk factor prevalence, and estimate
population-attributable risk (PAR) trends for each risk factor. In a population-based
cohort study of all residents of Olmsted County, Minnesota from 1981–2010, annual
incidence rates were calculated using incident VTE cases as the numerator and age-
and sex-specific Olmsted County population estimates as the denominator. Poisson regression
models were used to assess the relationship of crude incidence rates to year of diagnosis,
age at diagnosis, and sex. Trends in annual prevalence of major VTE risk factors were
estimated using linear regression. Poisson regression with time-dependent risk factors
(person-years approach) was used to model the entire population of Olmsted County
and derive the PAR. The age- and sex-adjusted annual VTE incidence, 1981–2010, did
not change significantly. Over the time period, 1988–2010, the prevalence of obesity,
surgery, active cancer and leg paresis increased. Patient age, hospitalisation, surgery,
cancer, trauma, leg paresis and nursing home confinement jointly accounted for 79
% of incident VTE; obesity accounted for 33 % of incident idiopathic VTE. The increasing
prevalence of obesity, cancer and surgery accounted in part for the persistent VTE
incidence. The PAR of active cancer and surgery, 1981–2010, significantly increased.
In conclusion, almost 80 % of incident VTE events are attributable to known major
VTE risk factors and one-third of incident idiopathic VTE events are attributable
to obesity. Increasing surgery PAR suggests that concurrent efforts to prevent VTE
may have been insufficient.
Supplementary Material to this article is available online at www.thrombosis-online.com.
Keywords
Venous thrombosis - pulmonary embolism - thrombophlebitis - phlebitis - epidemiology