Associations of Endometriosis and Hormone Therapy With Risk of Hyperlipidemia

Cherry Yin-Yi Chang; Chih-Hsin Muo; Yi-Chun Yeh; Chung-Yen Lu; William Wu-Chou Lin; Pei-Chun Chen

Disclosures

Am J Epidemiol. 2021;190(2):277-287. 

In This Article

Abstract and Introduction

Abstract

Using claims data from the universal health insurance program of Taiwan, we conducted a retrospective cohort study to investigate whether endometriosis and hormone therapy are associated with the risk of developing hyperlipidemia. We selected 9,155 women aged 20–55 years with endometriosis diagnosed during the period 2000–2013 and 212,641 women without endometriosis with a median follow-up time of 7 years. Among patients with endometriosis, 86% of cases were identified on the basis of diagnosis codes with an ultrasound claim, and 14% were defined by diagnostic laparoscopy or surgical treatments. In a Cox proportional hazards model, the adjusted hazard ratio was 1.30 (95% confidence interval (CI): 1.19, 1.41) for all women, 1.04 (95% CI: 0.81, 1.32) for women under 35 years of age, 1.17 (95% CI: 1.03, 1.32) for women aged 35–44 years, and 1.34 (95% CI: 1.18, 1.52) for women aged 45–54 years. Hysterectomy and/or bilateral oophorectomy accounted for 46.9% of the association between endometriosis and hyperlipidemia, and hormone therapy accounted for 21.6%. Among women with endometriosis, the marginal structural model approach adjusting for time-varying hysterectomy/bilateral oophorectomy showed no association between use of hormone medications and risk of hyperlipidemia. We concluded that women with endometriosis are at increased risk of hyperlipidemia; use of hormone therapy by these women was not independently associated with the development of hyperlipidemia.

Introduction

Endometriosis is a common, chronic gynecological disorder with an estimated prevalence of 6%–10% among women worldwide.[1] Accumulating evidence suggests that systemic chronic inflammation and oxidative stress, which contribute to the pathogenesis of atherosclerosis,[2,3] also play a role in the development and progression of endometriosis.[4–7] The involvement of lipids in the mechanisms of inflammation and atherosclerosis has been reported in several experimental studies. Excess low-density lipoprotein cholesterol may activate inflammatory processes in the arteries,[2,3,8] and long-term chronic inflammation is linked to lipid metabolism and may result in atherosclerosis.[8]

Case-control studies have shown that women with endometriosis are more likely to have unfavorable lipid profiles, with higher levels of low-density lipoprotein cholesterol and triglyceride and a lower level of high-density lipoprotein cholesterol than control subjects.[9–11] In Nurses' Health Study II, Mu et al.[12] recently demonstrated a temporal relationship between endometriosis and risk of developing hypercholesterolemia, and treatment factors such as hysterectomy/oophorectomy and postmenopausal hormone use partly accounted for the association. Although the study included a large number of subjects, the analysis included mainly female nurses from the United States, and information regarding use of hormonal medications for treatment of endometriosis, beyond the use of contraceptives, was not available. There remains a need for further studies to evaluate the association in other ethnic populations with comprehensive information on prescription of hormonal medications. Therefore, we investigated the association between endometriosis and subsequent risk of hyperlipidemia among Asian women using health insurance claims data from Taiwan. The role of hormone therapy in the risk of hyperlipidemia after diagnosis of endometriosis was also assessed.

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