Association between average daily television viewing time and the incidence of ovarian cancer: findings from the Japan Collaborative Cohort Study

Purpose: Seventy-five percent of epidemiological studies have reported that sedentary behavior is associated with ovarian cancer incidence. Although Japan has one of the most sedentary populations, with median sitting times of 7 h/day, this association has not been investigated. This study aimed to elucidate the association between average daily television (TV) viewing time, which is a major sedentary behavior, and the incidence of ovarian cancer in a large-scale nationwide cohort study in Japan. Methods: A total of 34,758 female participants aged 40–79 years without a history of cancer at baseline were included in the study. The inverse probability weighted competing risk model was used to calculate the hazard ratio (HR) and 95% confidence interval (CI) for the incidence of ovarian cancer. Results: During a median follow-up of 19.4 years, 59 participants developed ovarian cancer (ICD-10: C56), 2,706 participants developed other types of cancer, and 4,318 participants died. Participants who watched TV for ≥ 5 h/day were more likely to develop ovarian cancer than those who watched TV for < 2 h/day (HR 2.15; 95% CI 1.54–2.99). Conclusion: Our findings suggest that reducing the amount of time spent sedentarily may be beneficial for preventing ovarian cancer.