Table III.

History of laparoscopically confirmed endometriosis and risk of incident infertility among married women in Nurses' Health Study II from 1989 to 2005, stratified by primary versus secondary infertility, age and BMI categories

Laparoscopically confirmed endometriosis	Primary infertility			Secondary infertility			P-het
	No	Yes	P-value	No	Yes	P-value
Cases, n	2132	101		2297	82
Person-years	42 606	1409		310 883	7321
Age-adjusted HR (95% CI)	1.00 (ref)	1.81 (1.41–2.33)	<0.0001	1.00 (ref)	1.85 (1.38–2.49)	<0.0001
Multivariate-adjusted HRb (95% CI)	1.00 (ref)	1.79 (1.39–2.30)	<0.0001	1.00 (ref)	1.73 (1.29–2.33)	0.0003	0.54
Laparoscopically confirmed endometriosis	Age <35 years			Age 35–39 years			P-het
	No	Yes	P-value	No	Yes	P-value
Cases, n	2896	114		1533	69
Person-years	156 338	3038		197 151	5691
Age-adjusted HR (95% CI)	1.00 (ref)	2.12 (1.76–2.56)	<0.0001	1.00 (ref)	1.56 (1.23–1.99)	0.0003
Multivariate-adjusted HRa (95% CI)	1.00 (ref)	2.11 (1.74–2.54)	<0.0001	1.00 (ref)	1.57 (1.23–2.00)	0.0003
Multivariate-adjusted HRb (95% CI)	1.00 (ref)	1.77 (1.46–2.14)	<0.0001	1.00 (ref)	1.20 (0.94–1.53)	0.14	0.008
Laparoscopically confirmed endometriosis	BMI <25 kg/m2			BMI 25+ kg/m2			P-het
	No	Yes	P-value	No	Yes	P-value
Cases, n	3092	145		1326	37
Person-years	239 447	5626		113 012	3068
Age-adjusted HR (95% CI)	1.00 (ref)	2.44 (1.98–3.00)	<0.0001	1.00 (ref)	1.33 (0.85–2.09)	0.21
Multivariate-adjusted HRa (95% CI)	1.00 (ref)	2.46 (1.99–3.03)	<0.0001	1.00 (ref)	1.28 (0.82–2.00)	0.28
Multivariate-adjusted HRb (95% CI)	1.00 (ref)	1.96 (1.59–2.42)	<0.0001	1.00 (ref)	1.30 (0.83–2.05)	0.25	0.02

^aAdjusted for age (months), age interaction term (except for age stratified analysis), questionnaire cycle, age at menarche, menstrual cycle length between ages 18 and 22 years, current BMI, total physical activity, smoking status, cumulatively updated average AHEI diet score.

^bAdditionally adjusted the multivariate model for parity (number of children).