Table 2.

Baseline Characteristics of Study Participants, by Incident Invasive Breast Cancer Status, Women's Health Initiative Observational Study, 1994–1998

Characteristic	Incident Invasive Breast Cancer (n = 4,497)			No Incident Invasive Breast Cancer (n = 75,090)			P Value
	Mean (SD)	No.a	%	Mean (SD)	No.a	%
Age, years	63.3 (7.1)			63.3 (7.4)			0.47
BMIb	27.3 (5.7)			27.2 (5.9)			0.27
Age at menopause, years	48.4 (6.6)			47.4 (6.7)			<0.001
Resting pulse (30 seconds)	34.8 (6.1)			34.6 (6.0)			0.24
Ethnicity							<0.001
Non-Hispanic white		4,015	89.5		62,076	82.9
Black		226	5.0		6,247	8.3
Hispanic/Latino		102	2.3		3,023	4.0
Other		144	3.2		3,534	4.7
Educational level							<0.001
<College degree		2,309	51.7		43,422	58.3
≥College degree		2,161	48.3		31,050	41.7
Income							<0.001
<$20,000		514	12.3		11,191	16.1
$20,000–$49,999		1,775	42.4		30,067	43.2
$50,000–$74,999		925	22.1		14,064	20.2
≥$75,000		976	23.3		14,264	20.5
Marital status							0.001
Never married		231	5.2		3,417	4.6
Divorced/separated		667	14.9		11,948	16.0
Widowed		691	15.4		12,762	17.1
Married/living such		2,891	64.5		46,595	62.4
Smoking status							<0.001
Never smoker		2,141	48.1		38,080	51.4
Past smoker		2,035	45.7		31,344	42.3
Current smoker		274	6.2		4,735	6.4
Physical activity level							0.03
No activity		552	12.4		10,095	13.6
Mild		1,663	37.4		28,519	38.3
Moderate		864	19.4		13,697	18.4
Strenuous		1,372	30.8		22,086	29.7
Age at menarche, years							0.11
≤10		323	7.2		4,880	6.5
11–13		3,189	71.1		52,889	70.6
14–15		796	17.8		14,088	18.8
≥16		175	3.9		3,057	4.1
Age at first birth, years							<0.001
No term pregnancy		657	15.8		9,349	13.8
<20		413	9.9		8,651	12.8
20–29		2,672	64.3		43,991	65.1
≥30		411	9.9		5,606	8.3
Parity							<0.001
No term pregnancy		657	14.7		9,349	12.5
1		415	9.3		6,794	9.1
2–3		2,313	51.7		37,718	50.5
≥4		1,088	24.3		20,819	27.9
Hormone therapy use							<0.001
Never		1,541	34.3		29,883	39.8
Past		565	12.6		10,349	13.8
Current		2,384	53.1		34,792	46.4
Hysterectomy							<0.001
No		2,829	63.0		43,844	58.4
Yes		1,664	37.0		31,176	41.6
Hypertension							0.31
Nonhypertensive		3,022	68.1		49,860	67.3
Untreated		323	7.3		5,840	7.9
Treated		1,093	24.6		18,353	24.8
Diabetes (treated)							<0.001
No		4,359	97.0		71,881	95.9
Yes		135	3.0		3,113	4.2
High cholesterol requiring medication							0.15
No		3,791	86.0		62,877	85.3
Yes		615	14.0		10,874	14.7
History of CVD							<0.02
No		4,130	91.8		68,169	90.8
Yes		367	8.2		6,921	9.2
History of CHF							0.64
No		4,455	99.1		74,435	99.1
Yes		42	0.9		651	0.9
Warfarin use							0.22
No		4,438	98.7		74,254	98.9
Yes		59	1.3		835	1.1
Anti-arrhythmic use							0.29
No		4,474	99.5		74,783	99.6
Yes		23	0.5		306	0.4
Aspirin use							0.18
No		3,428	76.2		57,897	77.1
Yes		1,069	23.8		17,192	22.9
Statin use							0.25
No		4,157	92.4		69,054	92.0
Yes		340	7.6		6,035	8.0
β-blocker use							0.35
No		4,107	91.3		68,876	91.7
Yes		390	8.7		6,214	8.3
Calcium channel blocker use							0.95
No		4,065	90.4		67,853	90.4
Yes		432	9.6		7,237	9.6
ACE inhibitor use							0.44
No		4,159	92.5		69,207	92.2
Yes		338	7.5		5,883	7.8
Angiotensin II receptor blocker use							0.80
No		4,465	99.3		74,530	99.3
Yes		32	0.7		560	0.7
Cardiac glycoside use							<0.001
No		4,372	97.2		76,654	98.1
Yes		125	2.8		1,435	1.9

Abbreviations: ACE, angiotensin-converting enzyme; BMI, body mass index; CHF, congestive heart failure; CVD, cardiovascular disease; SD, standard deviation.

^a Subgroup totals may not sum to the column total because of missing data.

^b Weight (kg)/height (m)².