Uterine Fibroids and Hysterectomy - Risk Factors

Risk Factors

Uterine fibroids are the most common tumor found in female reproductive organs. It is estimated that over 50% of women between the ages of 30 and 50 have fibroids, although they cause symptoms in only about 25%. A recent survey of 1364 women suggested an even higher prevalence of over 80% in African American women and almost 70% in white women. A number of possible risk factors have been identified, but very little research exists to confirm or develop information on them.

Being African-American

Uterine fibroids are particularly common in African American women, with an estimated prevalence of 50% to 75%. These women are also more likely to have severe pain, anemia, and larger and more numerous fibroids than women in other population groups. Although genetics may play a role, women of African descent who live in other countries do not appear to have as high an incidence of fibroids. This suggests that diet or other environmental factors are at work in the development of fibroids in African American women.

High Exposure to Estrogen

Fibroids can start to grow soon after puberty, although usually they are detected when a woman reaches young adulthood. Women with fibroids are at risk for accelerated fibroid growth when estrogen levels are high or when lifestyle behaviors keep estrogen levels high.

Some examples of risk factors for fibroids that are also associated with high estrogen exposure include the following:

• Early onset of menstrual period (before age 12).
• Being overweight and sedentary.
• Never being pregnant. The risk for fibroids decreases with more children. (This risk factor, however, may be due to a greater risk for infertility caused by fibroids in the first place.)

Combined Oral Contraceptives. Combined oral contraceptives contain estrogen and progesterone and the evidence on their effects on fibroids have been conflicting. Early reports suggested they might be a risk factor. Most studies conducted more recently, however, have found no association and some even suggest that the newer low-dose OC combinations may be protective.

Hormone Replacement Therapy. Hormone replacement therapies (HRT) contain estrogen alone or estrogen plus progesterone. After menopause, fibroids usually shrink. Researchers, then, are investigating whether the hormones used in HRT could cause existing fibroids to persist or even grow. Some studies, but not all, have found greater fibroid growth with the use of patch-administered hormone agents. (In one of the studies taking oral estrogen however, had no effect.) A 2001 systematic review of studies reported some fibroid growth in women taking HRT, but usually without any significant symptoms. In summary, if HRT has an effect on fibroid growth, it is unlikely to be severe. Any increase in fibroid growth during menopause must be evaluated surgically by a gynecologist since such growth, even if a woman is on hormone replacement therapy, may mean cancer.

High Blood Pressure

High blood pressure (hypertension)may be associated with increased fibroid risk according to a 2005 epidemiologic study. The prospective study tracked women in the Nurses? Health Study for 10 years and found that for every 10 mm/Hg increase in diastolic blood pressure, the risk for developing fibroids increased by 8% to 10%. (Interestingly, women who used antihypertensive medications had the highest risk.). Researchers reported that women with hypertension were 24% more likely to develop fibroids and that the longer a woman had hypertension, the greater her risk.