Researchers assessed participants in the Nurses’ Health Study (NHS) and NHSII with the aim to determine if and how sedentary behavior is associated with risk of ovarian cancer overall, by tumor subtype, and by participant characteristics.

• Analysis was performed including a total of 69,558 NHS (1992-2016) and 104,130 NHSII (1991-2015) participants who reported sitting time at home, work, and watching television.

• There were 884 cases with histologically-confirmed ovarian cancer.

• Potential heterogeneity was examined by tumor histotype (type I and II), body mass index (BMI; < 25, ≥ 25), and total physical activity (< 15, ≥ 15 metabolic equivalent-hours/week).

• Analysis suggests an elevated risk of ovarian cancer for women who had longer sitting time at work [10-19 (HR = 1.25, 95%CI: 1.04-1.51) and ≥ 20 (HR = 1.40, 95%CI: 1.14-1.71) vs < 5 hours/week].

• No variation in this association was evident by BMI, physical activity, or histotype (P-heterogeneity ≥ 0.43).