Endometriosis risk and hormonal contraceptive usage: A nationwide cohort study.

OBJECTIVE

To investigate whether an early need of hormonal contraceptive (HC), or a failure to find a suitable method, are warning signs for endometriosis.

DESIGN

A retrospective cohort study.

SETTING

Sweden.

POPULATION: The cohort consisted of 720 805 women aged 12-27 years during the period 2005-2017. All women, regardless of whether they received a diagnosis of endometriosis or not (reference group), were included.

METHODS

We used data from Swedish national registers. Risks are expressed as crude and adjusted hazard ratios (HRs and aHRs, respectively) with 95% confidence intervals (95% CIs), adjusted for age, education level, civil status, parity, country of birth, and diagnoses of infertility, dysmenorrhea or depression.

MAIN OUTCOME MEASURES: A diagnosis of endometriosis between 12 and 27 years of age.

RESULTS

During this period, 3268 women were diagnosed with endometriosis (0.45%). Women who started HC at the ages of 12-14 years had a higher risk of receiving the diagnosis (aHR 2.53, 95% CI 2.21-2.90) than those who began at age 17 years or older. Having tried more types of HCs was associated with a twofold increased risk of endometriosis (more that three types of HC, aHR 2.31, 95% CI 1.71-3.12). Using HC for more than 1 year was associated with a decreased risk of endometriosis (>1 year, aHR 0.53, 95% CI 0.48-0.59). Women with endometriosis more commonly had dysmenorrhea, depression or infertility.

CONCLUSIONS

The use of HCs at an early age and a failure to find a suitable HC were identified as warning signs of later receiving an endometriosis diagnosis. A longer duration of HC usage reduced the risk of receiving the diagnosis.