Administrative health data sets to study endometriosis: a population-based approach

Endometriosis and cardiovascular disease: a population-based cohort study

BACKGROUND

Endometriosis, a prevalent condition among females of reproductive age, may be associated with increased risk of cardiovascular disease (CVD) through chronic inflammation and early menopause. The objective of this study was to estimate the association between endometriosis and subsequent risk of CVD.

METHODS

We conducted a population-based cohort study using administrative health data from Ontario residents from 1993 to 2015. We compared the incidence of CVD and cardiovascular health outcomes between females with endometriosis and 2 age-matched females without endometriosis. The primary outcome was hospital admission for CVD. Secondary outcomes included in-hospital CVD events of interest and emergency department visits for CVD. We used Cox proportional hazards models to estimate adjusted hazard ratios (HRs) between endometriosis and CVD events.

RESULTS

We identified 166 835 eligible patients with endometriosis and matched 333 706 patients without endometriosis. The mean age of those with endometriosis was 36.4 years. Patients with endometriosis had a higher incidence of hospital admission for CVD (195 admissions/100 000 person-years) compared with those without endometriosis (163 admissions/100 000 person-years). Similarly, the incidence of secondary CVD events was slightly higher among patients with endometriosis (292 cases/100 000 person-years) than among those without endometriosis (224 cases/100 000 person-years). Females with endometriosis had an increased risk of hospital admission (adjusted HR 1.14, 95% confidence interval [CI] 1.10-1.19) and secondary CVD events (adjusted HR 1.26, 95% CI 1.23-1.30).

INTERPRETATION

In this large, population-based study, endometriosis was associated with a small increased risk of CVD events. Future studies need to investigate potential etiological mechanisms and strategies to decrease long-term CVD risk in patients with endometriosis.

Mode of conception in patients with endometriosis and adverse pregnancy outcomes: a population-based cohort study

OBJECTIVE

To evaluate the association between endometriosis and adverse pregnancy outcomes.

DESIGN

Population-based retrospective cohort study using linked universal health databases through ICES Ontario.

PATIENT(S)

All singleton pregnancies with an estimated date of confinement between October 2006 and February 2014.

INTERVENTION(S)

Endometriosis was determined based on a surgical and/or medical diagnosis (defined as an in-hospital admission or surgery with a diagnosis code of International Classification of Diseases [ICD]9-617 or ICD10-N80 and/or 2 medical consults billed as ICD9-617).

MAIN OUTCOME MEASURE(S)

The association between endometriosis and pregnancy outcomes was quantified by relative risks, derived using modified Poisson regression, and adjusted for maternal age, income quintiles, and history of fibroids (aRR). Mediation analysis was conducted to estimate direct effects of endometriosis diagnosis and indirect effects through mode of conception, namely: infertility without fertility treatment (known infertility but conceived without assistance), ovulation induction or intrauterine insemination, and in vitro fertilization or intracytoplasmic sperm injection, relative to unassisted conception.

RESULT(S)

A total of 19,099 pregnancies had an antecedent diagnosis of endometriosis, while 768,350 did not. Mean time (standard deviation) from endometriosis diagnosis to the index pregnancy was 5.6 (4.3) years. Endometriosis was associated with an increased risk of hypertensive disorders of pregnancy (aRR, 1.09; 95% confidence interval [CI], 1.02-1.16), preterm birth <37 weeks (aRR, 1.26; 95% CI, 1.20-1.33), early preterm birth <34 weeks (aRR, 1.33; 95% CI, 1.17-1.50), placenta previa (aRR, 2.07; 95% CI, 1.84-2.33), placenta abruption (aRR, 1.55; 95% CI, 1.31-1.83), other placental disorders (aRR, 1.77; 95% CI, 1.36-2.30), cesarean delivery (aRR, 1.18; 95% CI, 1.16-1.21), and stillbirth (aRR, 1.32; 95% CI, 1.09-1.59). Mediation analysis suggests that endometriosis directly affects most adverse pregnancy outcomes studied, except for stillbirth where infertility diagnosis or fertility treatment indirectly accounted for part of the increased risk.

CONCLUSION(S)

Endometriosis was associated with adverse pregnancy, independent of infertility diagnosis, or fertility treatment. Future studies should investigate the mechanisms of action and potential interventions.