Abstract
BackgroundA cross-sectional study has reported that nickel allergy is associated with endometriosis. However, causal studies of this association are limited.ObjectiveThe objective of this study was to compare the prevalence of nickel allergy in women with and without endometriosis.MethodsWe used a National Health Insurance Service (NHIS) sample cohort dataset that included approximately 1 million individuals from South Korea; the data were obtained between January 01, 2002, and December 31, 2013. We selected the endometriosis group according to diagnosis code (N80.X), surgery codes, and drug codes during the years 2009~2013. The controls were randomly matched to the endometriosis patients at a ratio of 4:1 by age and socioeconomic status. Patients with nickel allergy were defined in the cohort dataset as those with a simultaneous diagnosis code (L23.0) and patch test code during 2002~2008.ResultsIn total, 4,985 women were selected from the NHIS cohort database and divided into an endometriosis group (997 women) and a control group (3,988 women). The number of patients with nickel allergy in the endometriosis group was eight (0.8%), and that in the control group was thirteen (0.3%). After adjustment for age and socioeconomic status, the rate of nickel allergy in was higher in the endometriosis group than in the control group [odds ratio: 2.474; 95% confidence interval: 1.023~5.988; p = 0.044].ConclusionsWe found that nickel allergy is a risk factor for endometriosis.
Highlights
Endometriosis is an estrogen-dependent disease that causes pelvic pain and subfertility in 6–10% of women [1]
4,985 women were selected from the National Health Insurance Service (NHIS) cohort database and divided into an endometriosis group (997 women) and a control group (3,988 women)
After adjustment for age and socioeconomic status, the rate of nickel allergy in was higher in the endometriosis group than in the control group [odds ratio: 2.474; 95% confidence interval: 1.023~5.988; p = 0.044]
Summary
Endometriosis is an estrogen-dependent disease that causes pelvic pain and subfertility in 6–10% of women [1]. Debate continues regarding the cause of endometriosis, the central theory involves the retrograde flow of endometrial cells into the pelvic cavity during menstruation [1,2]. One hypothesis is that environmental substances such as dioxin, polychlorinated biphenyls and organochlorine pesticides may cause endometriosis [3,4]. Another hypothesis is that changes in the immune response might affect the survival of endometrial cells external to the endometrium [5,6]. The study of Yuk et al was not a causal study but rather a correlational study It is unclear which disease precedes the other.
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