Objective Prolonged seated immobility during long-distance flights is related to an increased risk of venous thromboembolism (VTE) but little is known on the risk, if any, related to sedentary work. The objective of this paper was to examine the risk of VTE according to sitting posture at work.

Methods A total of 88 077 participants from the Copenhagen City Heart Study and the Copenhagen General Population Study were included in the study cohort, all without previous thromboembolic events and aged below 65 years. Activity level at work was obtained at baseline through self-administered questionnaires. VTEs were identified through national patient registries with complete coverage. Survival analyses were performed to determine the risk of VTE according to activity level at work with adjustment for a range of known determinants including lifestyle and coagulation factors.

Results During the follow-up period of 5 79 116 person years (mean follow-up, 7 years) 805 participants experienced their first venous thromboembolic event. 42% of the population categorised themselves as sedentary workers. Multivariable adjusted analyses showed no difference in risk of VTE between sedentary and walking work [hazard ratio (HR) 0.95 (95% confidence interval (CI), 0.80–1.14)]. Likewise, when considering activity level at work on a continuous scale, defined by Metabolic equivalents (METs), multivariable adjusted HR for 1 MET increase was 1.04 (95% CI 0.96–1.13).

Conclusion Sedentary work defined by a wide-range group of occupations, is not a risk factor for VTE. Whether certain occupations with particularly high exposure to immobilised sitting positions are associated with thromboembolic events is not addressed.