Table 1.

Studies of demographic or environmental parameters

Reference	Sample Size	Involved factors	Population	Summary
Yasui et al., 2015[20]	Cohort: 330	Menstrual cycle	Japanese	Surgically confirmed endometriosis (Group A, n=210), imaging diagnosed endometriosis without a surgical procedure (Group B, n=120). A short menstrual cycle at 18-22 years of age and cigarette smoking at 30 years of age were associated with significantly increased risk of endometriosis (Group A + Group B)
		Infertility
		Cigarette smoking
				In women with a history of infertility, a short menstrual cycle was associated with a significantly increased risk of endometriosis in both Group A and Group B, but risk profiles of endometriosis were different between Group A and Group B in women without a history of infertility
Yi et al., 2009[21]	Cohort: 481	BMI	Korean	Women in stages III or IV endometriosis had a significantly lower BMI than those in stages I or II disease
Itoh et al., 2008[22]	Case: 54	Cadmium	Japanese	No association between higher urinary cadmium concentration and the risk of endometriosis
	Control: 74
Tsukino et al., 2005[23]	Case: 58	Organochlorine	Japanese	No association between higher serum levels of these organochlorine compounds and an increased risk of endometriosis among infertile Japanese women
	Control: 81
Kashima et al., 2004[24]	Case: 339	Family history	Japanese	Heritable genetic factors contribute to the development of endometriosis
	Control: 284

BMI: Body mass index