IUD Study Misinterpretations Spark Public Fear and Confusion

A recent study published in JAMA Network has revealed that women using hormone-releasing intrauterine devices (IUDs) face a breast cancer risk similar to those taking hormonal birth control pills. Conducted by researchers at the Danish Cancer Institute, the study suggests a slight increase in breast cancer risk among users of hormonal IUDs compared to non-users. However, experts caution that the findings should be interpreted with care due to uncertainties in the data.

The research analyzed health data from 78,595 Danish women aged 15 to 49 who used levonorgestrel-releasing IUDs, such as Mirena or Kyleena, between 2000 and 2019, as reported by Euro News. The study compared these women with a control group composed of women from Danish registries who did not use hormonal contraceptives, which could introduce sample bias. Participants were monitored over an average of 6.8 years, until they either received a breast cancer diagnosis, became pregnant, started hormone therapy after menopause, moved out of the country, passed away, or reached the study’s end in 2022, according to Medical Daily.

The study showed that hormonal IUD use was associated with 14 additional cases of breast cancer per 10,000 women, according to Euro News. However, certain aspects of this study have been incorrectly interpreted by media reports, as noted by The University of Western Australia (UWA), which may be creating unnecessary concern among the public. Such reporting may lead the audience to believe that their individual risk is heightened; however, the absolute risk is measured per 10,000 cases, which is not representative of individual experiences.

More precisely, the relative risk of breast cancer increased in women with prolonged use of hormonal IUDs: those using them for up to five years faced a 30% higher risk, which rose to 40% after 5 to 10 years, and 80% after 10 to 15 years. However, researchers noted that the absolute increase in risk remained relatively low, with the study estimating an additional 14, 29, and 71 cases of breast cancer per 10,000 women over the respective periods. Each of these figures accounts for less than 1% of the total group (10,000 women). As such, while there may be a slight increase in relative risk per group, the study suggests that the overall absolute risk of developing breast cancer from hormonal IUD use remains minimal.

Furthermore, according to the UWA, this study compared women who chose hormonal IUDs with those who did not, potentially introducing differences beyond IUD use alone. Although researchers adjusted for age, education, and medical history, they overlooked factors like body weight, alcohol use, and smoking, adding uncertainty to the results. These independent risk factors are known to contribute to breast cancer in women, irrespective of contraceptive use.

The findings arrive during a period of increasing popularity for this contraceptive method in various countries, including Mexico. According to the National Survey of Demographic Dynamics, birth control pills, female sterilization, IUDs, injections, and condoms are among the most recognized contraceptive methods for Mexican women. ?