Table 1.

Age-standardized characteristics of the study population at the midpoint of follow-up in the Nurses’ Health Study (2000) and Nurses’ Health Study II (2001)

	Nurses’ Health Study (2000)			Nurses’ Health Study II (2001)
	Total cumulative average leisure-time physical activity, MET-h/week
	<3	9 to <18	≥27	<3	9 to <18	≥27
Subjects (n)	4734	15378	9365	5124	19928	16567
Cumulative average activity, MET-h/week	1.8 (0.8)1	13.2 (2.6)	40.1 (12.5)	1.8 (0.8)	13.2 (2.6)	42.3 (14.2)
Recent activity, MET-h/week	1.7 (2.1)	13.5 (11.0)	39.9 (25.1)	2.1 (2.6)	15.0 (12.5)	40.0 (26.7)
Baseline activity, MET-h/week	1.9 (2.2)	11.0 (9.9)	33.4 (23.8)	2.7 (2.6)	15.6 (12.7)	43.7 (27.4)
Age, years	66.3 (7.2)	66.0 (7.1)	66.0 (7.0)	47.3 (4.6)	46.5 (4.6)	45.9 (4.7)
Ever OC use, %	47	49	50	85	85	85
Duration of OC use, months2	49.9 (45.9)	51.0 (46.1)	50.8 (46.7)	67.5 (60.3)	67.7 (59.2)	70.2 (62.3)
Postmenopausal, %	97	98	98	17	15	15
Ever estrogen PMH use, %3	19	20	21	5	4	4
Duration of estrogen-only PMH use, months2	86.6 (78.4)	93.8 (80.6)	94.0 (80.7)	2.1 (2.4)	1.9 (1.7)	2.0 (1.9)
Ever estrogen-progestin PMH use, %3	32	37	39	51	56	56
Duration of estrogen-progestin PMH use, months2	61.4 (47.6)	65.2 (48.2)	67.0 (48.7)	3.0 (2.4)	2.7 (2.3)	2.6 (2.3)
History of tubal ligation, %	20	21	21	26	24	22
History of hysterectomy, %	23	23	21	9	9	9
Family history of breast or ovarian cancer, %	19	20	20	13	14	14
Parous, %	95	95	94	85	84	77
Number of children in parous women	3.3 (1.6)	3.2 (1.5)	3.2 (1.5)	2.3 (1.0)	2.3 (0.9)	2.3 (0.9)
Caffeine, mg/day	233.3 (225.9)	208.8 (201.7)	203.9 (194.4)	234.5 (224.4)	226.6 (209.4)	226.9 (206.1)
Lactose, g/day	14.8 (12.6)	16.4 (12.1)	16.7 (12.1)	15.8 (13.2)	17.7 (13.1)	18.5 (13.4)
Body mass index, kg/m2	28.9 (6.7)	26.7 (5.0)	25.0 (4.3)	29.5 (8.1)	26.8 (6.1)	25.1 (5.1)

¹Mean (SD) for all such values

²Duration among ever users

³Among postmenopausal women