Endometriosis and systemic lupus erythematosus

a population-based case–control study

Harris, H R
Simard, J F
Arkema, E V

¹Division of Nutritional Epidemiology, The National Institute for Environmental Medicine, Karolinska Institute, Stockholm, Sweden
²Obstetrics and Gynecology Epidemiology Center, Brigham and Women’s Hospital, Boston, Massachusetts, USA
³Clinical Epidemiology Unit, Department of Medicine Solna, Karolinska Institute, Stockholm, Sweden
⁴Division of Epidemiology, Department of Health Research and Policy, Stanford School of Medicine, Stanford, USA
⁵Division of Immunology & Rheumatology, Department of Medicine, Stanford School of Medicine, Stanford, USA

H Harris, Unit of Nutritional Epidemiology, Institute for Environmental Medicine, Karolinska Institutet, PO Box 210, SE-171 77 Stockholm, Sweden. Email: [email protected]

Received October 14, 2015

Accepted January 18, 2016

Lupus 25(9):p 1045-1049, August 2016. | DOI: 10.1177/0961203316631635

Objective

To investigate the association between endometriosis and systemic lupus erythematosus (SLE) in prospectively collected population-based data.

Methods

We conducted a case–control study using Swedish registers, identifying female SLE cases from the National Patient Register and female controls sampled from the general population matched on birth year, sex and county during 1964–2011. We identified endometriosis diagnoses from the National Patient Register using ICD codes. We estimated odds ratios and 95% confidence intervals using conditional logistic regression models.

Results

We identified 2834 cases of SLE and 14,164 controls. Seventy-eight cases were diagnosed with endometriosis prior to their SLE diagnosis and 288 controls were diagnosed prior to the index date. We observed a significant association between endometriosis and subsequent SLE with an odds ratio of 1.39 (95% confidence interval = 1.09–1.78). The association was similar when requiring a laparoscopy/laparotomy within six months of the endometriosis diagnosis (odds ratio = 1.33; 95% confidence interval = 0.84–2.12) while the association was stronger when restricted to endometriosis diagnosed at the same time as hysterectomy (odds ratio = 2.26; 95% confidence interval = 1.47–3.64).

Conclusions

Our findings suggest an association between endometriosis and SLE. Future prospective studies with extended follow-up will be necessary to clarify whether this association is influenced by the timing and severity of endometriosis diagnosis.