Abstract P209: Accelerometer-Measured Sedentary Behaviors and Venous Thromboembolism Risk Among Older Women

Introduction: Venous insufficiency, which can occur with prolonged sedentary behavior, is associated with venous thromboembolism (VTE) risk. Whether accelerometer-measured sedentary behaviors are associated with VTE risk is unknown. Hypothesis: Longer total sitting times, mean sitting bout durations, and time spent in prolonged sitting bouts are associated with a greater risk of incident VTE. Methods: We studied participants of the Women’s Health Initiative (WHI) Objective Physical Activity and Cardiovascular Health (OPACH) study without prior VTE, with adherent accelerometer wear, and with sedentary behavior data (n=5,591). Between May 2012-April 2014, participants wore the ActiGraph GT3X+ triaxial accelerometer at the hip for 7 days. Three sedentary behavior measures were classified using the Convolutional Neural Network Hip Accelerometer Posture algorithm: total sitting time, mean sitting bout duration, and time spent in prolonged (≥30 minutes) sitting bouts. VTE events were centrally adjudicated. Multivariable-adjusted (Table) Cox models estimated HRs and 95% CIs for each sedentary behavior in relation to VTE risk. Women were censored at death, loss to follow-up, or end of follow-up (February 2023). Mediation by BMI was evaluated for behaviors associated with VTE. Results: On average, participants were 79 years old. Over a mean follow-up of 8.2 years, 229 women experienced a VTE. In primary confounder-adjusted models, longer mean sitting bout durations were associated with greater incident VTE risk (HR per 5-minute increase=1.15; 95% CI: 1.04, 1.28) (Table). BMI mediated approximately 30% of this association (p<0.01). We found no significant evidence that total sitting time nor time spent in prolonged sitting bouts were associated with VTE. Conclusions: Longer mean sitting bout duration was associated with greater VTE risk, with substantial mediation by BMI. Our results suggest that reducing sedentary bout length in older women may reduce VTE risk.