6 hours or more/day of sedentary leisure time to double the risk of fibroids

Sedentary behaviour is associated with tumours that rely on the female hormone oestrogen, such as endometrial, ovarian, and breast cancers; uterine fibroids are also fuelled by oestrogen. Uterine fibroids are the most common benign tumours in women of childbearing age, varying in prevalence from 4.5% to 69%, say the researchers.

Clocking up 6 or more hours of sedentary leisure time every day may double a woman’s risk of uterine fibroids before she’s gone through the menopause, suggests research published in the open access journal BMJ Open.

The risk of these benign, but potentially large and painful, womb growths seems to rise in tandem with the amount of time spent sitting or lying down during the day, the findings suggest. The study sample included 6623 women aged 30 to 55 who had not yet gone through the menopause.

Sedentary behaviour was classified as 1.5 or fewer metabolic equivalent of task (MET) hours/day when sitting or lying down. METs express how much energy in calories is expended per hour of physical activity.

Participants were asked to specify how much time they spent playing board games, on screen time, reading, knitting and other similar activities and were then divided into four sedentary leisure time groups: under 2 hours/day; 2–3.99 hours/day; 4–5.99 hours/day; and 6 or more hours/day.

Around 6 out of 10 (61%) of the women clocked up 2–3.99 hours/day of sedentary leisure time. In all, 562 (8.5%) of the women had uterine fibroids, the prevalence of which increased with age. Rates were highest (2.5 times higher) among those aged 50 and older.

Weight (BMI), number of live births (more than 2), menstrual status, time since last live birth (13-17 years onwards), physical activity and sedentary leisure time were all associated with uterine fibroids.

“This cross-sectional study, based on the natural population, showed that [sedentary leisure time] has a linear positive correlation with [uterine fibroids], indicating that [it] may be an independent risk factor,” they conclude.

Reference: Association between leisure sedentary behaviour and uterine fibroids in non menopausal women: a population based study; BMJ Open, DOI: 10.1136/bmjopen-2023-073592