Table 1.

Age-adjusted characteristics of the study population by duration of oral contraceptive (OC) use at study baseline in 1989: Nurses’ Health Study II (n = 107,069)

	Duration of OC use, categorical
	Never use (n = 18,636)	≤ 1 year (n = 17,987)	> 1–5 years (n = 39,180)	> 5–10 years (n = 23,817)	> 10 years (n = 7,449)
Age, years*	34.0 (24.0–44.0)	35.0 (24.0–44.0)	34.0 (24.0–44.0)	34.0 (24.0–44.0)	35.0 (25.0–43.0)
Age at menarche, years	12.0 (9.0–17.0)	12.0 (9.0–17.0)	12.0 (9.0–17.0)	12.0 (9.0–17.0)	12.0 (9.0–17.0)
BMIa, categorical
BMI < 25 kg/m2, %	68.0	70.7	70.6	72.0	72.5
BMI 25-<30 kg/m2, %	18.6	18.2	18.2	18.3	17.9
BMI ≥ 30 kg/m2, %	13.4	11.1	11.1	9.7	9.6
Ever parous, %	60.6	74.8	75.4	71.0	58.1
Number of full-term pregnancies (among parous women)	2.0 (1.0–10.0)	2.0 (1.0–15.0)	2.0 (1.0–9.0)	2.0 (1.0–8.0)	2.0 (1.0–6.0)
Breastfeeding duration, in months (among parous women who ever breastfed)	11.5 (1.5–95.0)	10.0 (1.5–91.0)	10.0 (1.5–95.0)	9.0 (1.5–76.0)	9.0 (1.5–75.0)
Menopausal status
Premenopausal, %	99.5	99.5	99.6	99.7	99.6
Postmenopausal, %	13.4	11.1	11.1	9.7	9.6
Ever use of other contraceptive methods
IUDb or diaphragm, %	18.1	16.2	13.6	10.4	7.0
Male contraception, %	32.7	34.2	32.7	28.0	21.9
Tubal ligation, %	9.8	16.4	18.2	17.5	13.1
Other, %	23.6	18.9	15.7	13.1	11.4
Diagnosis of endometriosisc, %	2.1	3.6	3.5	3.2	3.1
Diagnosis of PCOSd, %	3.8	6.4	5.7	5.1	4.8
Postmenopausal HTe use, %	0.2	0.2	0.2	0.1	0.2
Arterial hypertension, %	5.2	5.3	5.3	4.8	5.4
Diabetes mellitus, %	1.3	0.8	0.7	0.5	0.6
Smoking status
Never smoker, %	77.2	67.5	65.5	58.7	54.8
Past smoker, %	14.1	20.4	21.8	25.3	25.6
Current smoker, %	8.7	12.1	12.7	16.0	19.6

Values are medians and ranges or percentages and are standardized to the age distribution of the study population

Values of polytomous variables may not sum to 100% due to rounding

*Value is not age adjusted

^aBody mass index

^bIntrauterine device

^cLaparoscopically confirmed endometriosis

^dPolycystic ovary syndrome

^eHormone therapy