Table 1.

Characteristics^a of the Study Population According to Postmenopausal Hormone Use and Number of Childbirths, Nurses’ Health Study, 1990

	PMH Useb						No. of Childbirths
	Never Use (n = 24,452)		Past Use (n = 14,394)		Current Use (n = 22,916)		0 (Nulliparous) (n = 6,715)		1–3 (n = 62,034)		≥4 (n = 30,770)
	Mean	%	Mean	%	Mean	%	Mean	%	Mean	%	Mean	%
Age, years	60 (5)c		62 (5)		59 (6)		58 (7)		56 (7)		59 (6)
Past PMH useb				100				24		22		22
Current PMH useb						100		42		41		34
Duration of PMH useb,d, years			3		8		7		6		5
Past use of oral contraceptives		34		41		45		37		49		48
Duration of oral contraceptive usee, years	4		4		4		4		4		4
Age at menopauseb, years	50		47		48		47		48		49
Age at menarche, years	13		12		13		12		12		12
Nulliparity		6		8		8		100
Parityf, no. of childbirths	3		3		3
Body mass indexg	26		26		25		26		26		26
Pack-years of smoking	16		17		13		14		13		14
Hypertension		35		39		35		31		31		31
Alcohol intake, g/day	5		5		5		6		5		5
Fruit intake, servings/day	2		2		2		2		2		2
Vegetable intake, servings/day	3		3		3		3		3		3

Abbreviation: PMH, postmenopausal hormone(s).

^aAll values were standardized to the age distribution of the study, except those for age.

^bAmong postmenopausal women only. We considered women who reported that their menstrual periods had ceased or who had undergone bilateral oophorectomy as having been postmenopausal since the time this had occurred. Women who reported cessation of menses after a simple hysterectomy or removal of only 1 ovary or who did not report the reason for cessation were considered postmenopausal when they reached the age at which natural menopause had occurred in 90% of the cohort (54 years for a current smoker and 56 years for a nonsmoker).

^cNumbers in parentheses, standard deviation.

^dCalculated among ever users of PMH only.

^eCalculated among ever users of oral contraceptives only.

^fCalculated among parous women only.

^gWeight (kg)/height (m)².