Objective: To determine the risk of venous thromboembolism (VTE) associated with prolonged work- and computer-related seated immobility.
Design: Case-control study in which cases were patients aged 18-65 years attending outpatient VTE clinics, and controls were patients aged 18-65 years admitted to CCU with a condition other than VTE. Interviewer-administered questionnaires obtained detailed information on VTE risk factors and clinical details.
Setting: VTE Clinics and Coronary Care Unit (CCU), Wellington and Kenepuru Hospitals, Wellington between February 2007 and February 2009.
Main outcome measure: The relative risk of VTE associated with prolonged work- and computer-related seated immobility, defined as being seated at work and on the computer at home, at least 10 hours in a 24-hour period and at least 2 hours at a time without getting up, during the four weeks prior to the onset of symptoms that led to VTE diagnosis or CCU admission.
Results: There were 197 cases and 197 controls. Prolonged work- and computer-related seated immobility was present in 33/197 (16.8%) and 19/197 (9.6%) cases and controls, respectively. In multivariate analyses, prolonged work- and computer-related seated immobility was associated with an increased risk of VTE, odds ratio 2.8 (95% CI 1.2-6.1, P=0.013). The maximum and average number of hours seated in a 24-hour period were associated with an increased risk of VTE, with odds ratios of 1.1 (95% CI 1.0-1.2, P=0.008) and 1.1 (95% CI 1.0-1.2, P=0.014) per additional hour seated.
Conclusion: Prolonged work- and computer-related seated immobility increases the risk of VTE. We suggest that there needs to be both a greater awareness of the role of prolonged work-related seated immobility in the pathogenesis of VTE, and the development of occupational strategies to decrease the risk.