Table 1.

Distribution of Baseline Characteristics Among 118,164 Participants Included in the Present Analysis, the California Teachers Study, 1995–1996^a

Baseline Characteristics	No.	%
Age at cohort enrollment, years
22–39	21,237	18.0
40–49	32,363	27.4
50–59	30,207	25.6
60–69	20,681	17.5
70–79	13,676	11.6
Age at menarche, yearsb
≤11	26,597	22.8
12	32,016	27.5
13	34,326	29.4
≥14	23,613	20.3
OC use
Never used	35,596	31.3
Former user at baseline	6,659	5.9
Current user at baseline	71,220	62.6
Ever used, unknown if current or former	256	0.2
Duration of OC use, yearsc
<1	8,947	11.8
1–4	26,355	34.7
5–9	24,076	31.7
≥10	16,488	21.7
Parity
Nulligravid	23,906	20.6
Gravid, nulliparous	7,124	6.1
1–2 full-term pregnancies	56,306	48.5
≥3 full-term pregnancies	28,721	24.7
Age at first full-term pregnancy, yearsd
≤19	4,479	5.3
20–24	26,629	31.3
25–29	34,541	40.6
30–34	14,782	17.4
≥35	4,595	5.4
Breastfeeding historye
Never breastfed	19,009	22.5
Ever breastfed	65,796	77.5
Menopausal status/HT use
Premenopausal	47,993	43.5
Postmenopausal, never used HT	13,956	12.7
Postmenopausal, ever used HTf	46,922	43.1
HT usef,g
Past HT user	8,803	19.7
Current user of ET	15,508	34.7
Current user of EPT	20,334	45.5
Age at menopause, yearsh
≤46	13,067	28.2
47–49	9,083	19.6
50–52	12,666	27.3
≥53	11,571	24.9
Body mass indexi
<25	69,318	60.8
25 to <30	28,388	24.9
≥30	16,221	14.2
Smoking history
Never	77,619	65.7
Former	33,779	28.6
Current	6,084	5.2
History of diabetes	3,298	2.8

Abbreviations: EPT, estrogen-plus-progestin therapy; ET, estrogen-only therapy; HT, hormone therapy; OC, oral contraceptive.

^a Numbers shown do not include subjects with missing information on pregnancy history (n = 2,107), body mass index (n = 4,237), smoking status (n = 682), age at menarche (n = 1,558), OC use (n = 4,433), duration of OC use (n = 6,702), age at first full-term pregnancy (n = 1), breastfeeding (n = 1), menopausal status/HT use (n = 9,293), age at menopause (n = 18,886), and HT use (n = 1,297).

^b Fifty-four participants who had never had a first menstrual period are not shown.

^c Among OC users.

^d Among parous participants.

^e Among participants who ever had a live birth (n = 84,807).

^f Excludes participants who used a progestin-only therapy (n = 980).

^g Among ever HT users.

^h Among postmenopausal participants.

ⁱ Weight (kg)/height (m)².