Table 1.

Characteristics of study participants (N=238), Wisconsin Breast Density Study, 2008-2009.

	N	%	25(OH)D (ng/mL) Mean (SD)
Age
55-59	126	52.9	34.2 (9.6)
60-64	64	26.9	34.5 (9.5)
65-70	48	20.2	34.0 (12.4)
			Ptrend = 0.95
Body mass index (kg/m2)
<18.5	2	0.8	33.6 (3.4)
18.5-24.9	72	30.3	38.5 (9.5)
25.0-29.9	76	31.9	34.0 (9.2)
≥30.0	86	36.1	31.0 (10.2)
Missing	2	0.8	-
			Ptrend < 0.0001
First degree family history of breast cancer
No	182	76.5	34.0 (9.8)
Yes	56	23.5	35.0 (11.3)
			Ptrend = 0.52
Age at menarche (years)
≤11	58	24.4	34.1 (10.8)
12-13	137	57.6	34.0 (10.1)
≥14	43	18.1	35.4 (9.7)
			Ptrend = 0.55
Parity
0	59	24.8	35.7 (10.1)
1	30	12.6	31.6 (9.7)
2	84	35.3	34.2 (9.9)
≥3	65	27.3	34.4 (10.8)
			Ptrend = 0.65
Age at first birth (years)*
<24	69	38.6	33.4 (10.7)
24-29	67	37.4	34.3 (10.5)
≥30	43	24.0	33.6 (9.1)
			Ptrend = 0.84
Age at menopause (years)
<50	64	26.9	33.6 (10.2)
50-54	127	53.4	34.2 (10.0)
≥55	42	17.7	34.7 (10.3)
Missing	5	2.1	-
			Ptrend = 0.58
Education
High school	44	18.5	33.4 (10.7)
Some college	54	22.7	31.7 (9.7)
College diploma	71	29.8	35.1 (9.7)
Advanced degree	69	29.0	36.0 (10.4)
			Ptrend = 0.05
Alcohol consumption (drinks/wk)†
None	85	35.7	34.4 (10.2)
<5 per week	112	47.1	33.7 (10.5)
≥5 per week	30	12.6	35.4 (8.7)
Missing	11	4.6	-
			Ptrend = 0.88
Vigorous physical activity (hours per week)‡
0-1.0	71	29.8	33.2 (9.6)
1.1-4.0	82	34.5	34.4 (10.5)
>4.0	85	35.7	35.0 (10.4)
			Ptrend = 0.29
Smoking history (pack-years)
None	144	60.5	34.6 (10.3)
1-15	45	18.9	34.3 (9.6)
>15	40	16.8	34.2 (11.2)
Missing	9	3.8	-
			Ptrend = 0.79
Vitamin D supplement use
No	58	24.4	27.7 (8.5)
Yes	180	75.6	36.4 (9.8)
			Ptrend < 0.0001

SD, standard deviation.

^*Among parous women only.

^†Includes beer, wine, and hard liquor.

^‡Physically vigorous activities that cause large increases in heart rate or breathing, such as sports activities, climbing stairs, heavy gardening, or lifting/carrying heavy objects.