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Table 2 Multivariatea comparisons of personal and family health history, socioeconomic, and other characteristics of women with breast cancer and controls in Marin County, California, 1997–99

From: Risk factors for breast cancer in a population with high incidence rates

   All women Women aged 50 years and over Women under 50 years of age
Variable (Total N)a Cases N (%)(285) Controls N (%)(286) Multivariate OR (95% CI) Cases N (%)(201) Controls N (%)(201) Multivariate OR (95% CI) Cases N (%)(84) Controls N (%)(85) Multivariate OR (95% CI)
Personal and family health history
First-degree relative with breast cancer
   No 231 (81.1) 230 (80.4) 1.0 162 (80.6) 157 (78.1) 1.0 69 (82.1) 73 (85.9) 1.0
   Yes 54 (18.9) 56 (19.6) 0.95 (0.58–1.5) 39 (19.4) 44 (21.9) 0.84 (0.47–1.5) 15 (17.9) 12 (14.1) 1.3 (0.40–4.0)
Benign biopsy history
   None 196 (68.8) 213 (74.5) 1.0 128 (63.7) 145 (72.1) 1.0 68 (81.0) 68 (80.0) 1.0
   Fine-needle aspiration only 16 (5.6) 19 (6.6) 0.74 (0.34–1.6) 14 (7.0) 10 (5.0) 1.4 (0.48–3.8) 2 (2.4) 9 (10.6) 0.13 (0.02–0.98)
   Surgical biopsyb 73 (25.6) 54 (18.9) 1.1 (0.66–1.7) 59 (29.4) 46 (22.9) 0.97 (0.56–1.7) 14 (16.7) 8 (9.4) 0.78 (0.22–2.9)
Previous radiation treatment
   No 252 (88.4) 266 (93.0) 1.0 174 (86.6) 185 (92.0) 1.0 78 (92.9) 81 (95.3) 1.0
   Yes 33 (11.6) 20 (7.0) 1.7 (0.89–3.3) 27 (13.4) 16 (8.0) 1.6 (0.76–3.5) 6 (7.1) 4 (4.7) 6.1 (1.1–34.9)
Age at menarche
   15 or more years old 18 (6.3) 26 (9.1) 1.0 14 (7.0) 18 (9.0) 1.0 4 (4.8) 8 (9.4) 1.0
   12–14 years old 220 (77.2) 197 (68.9) 1.5 (0.74–3.1) 152 (75.6) 132 (65.7) 1.3 (0.52–3.1) 68 (81.0) 65 (76.5) 2.6 (0.53–12.5)
   11 or less years old 47 (16.5) 63 (22.0) 1.2 (0.51–2.6) 35 (17.4) 51 (25.4) 0.74 (0.27–2.0) 12 (14.3) 12 (14.1) 2.5 (0.37–16.5)
Menopause status
   Premenopausal 81 (28.4) 66 (23.1) 1.0 13 (6.5) 7 (3.5) 1.0 68 (81.0) 59 (69.4) 1.0
   Perimenopausal 29 (10.2) 31 (10.8) 0.52 (0.26–1.0) 19 (9.5) 13 (6.5) 0.76 (0.19–3.0) 10 (11.9) 18 (21.2) 0.17 (0.05–0.59)
   Postmenopausal 175 (61.4) 189 (66.1) 0.40 (0.19–0.84) 169 (84.1) 181 (90.0) 0.45 (0.14–1.5) 6 (7.1) 8 (9.4) 0.38 (0.06–2.3)
Reproductive history
   Never pregnant 45 (15.8) 51 (17.8) 1.0 23 (11.4) 38 (18.9) 1.0 22 (26.2) 13 (15.3) 1.0
   Pregnant, no birth 27 (9.5) 23 (8.0) 1.4 (0.65–3.0) 15 (7.5) 11 (5.5) 2.2 (0.75–6.3) 12 (14.3) 12 (14.1) 0.52 (0.12–2.4)
   Birth, did not breastfeed 57 (20.0) 33 (11.5) 1.9 (0.97–3.9) 53 (26.4) 30 (14.9) 2.6 (1.1–5.8) 4 (4.8) 3 (3.5) 1.9 (0.22–16.0)
   Breastfed 156 (54.7) 179 (62.6) 0.98 (0.58–1.7) 110 (54.7) 122 (60.7) 1.4 (0.68–2.7) 46 (54.8) 57 (67.1) 0.35 (0.11–1.1)
Reproductive history, recategorization of those who had given birth versus never pregnant a
One birth 53 (18.6) 55 (19.2) 1.0 (0.54–2.0) 36 (17.9) 33 (16.4) 1.4 (0.62–3.4) 17 (20.2) 22 (25.9) 0.36 (0.09–1.4)
Two births 86 (30.2) 88 (30.8) 1.1 (0.59–1.9) 61 (30.3) 60 (29.9) 1.4 (0.66–3.0) 25 (29.8) 28 (32.9) 0.51 (0.15–1.8)
Three or more births 74 (26.0) 69 (24.1) 1.3 (0.68–2.4) 66 (32.8) 59 (29.4) 1.9 (0.89–4.1) 8 (9.5) 10 (11.8) 0.18 (0.04–0.90)
Reproductive history, recategorization of those who had breastfed versus never pregnant a
Breastfed 6 months or less 62 (21.8) 71 (24.8) 0.87 (0.47–1.6) 50 (24.9) 54 (26.9) 1.2 (0.57–2.7) 12 (14.3) 17 (20.0) 0.40 (0.1–1.7)
Breastfed 7–12 months 41 (14.4) 42 (14.7) 1.3 (0.65–2.6) 26 (12.9) 29 (14.4) 1.6 (0.65–3.8) 15 (17.9) 13 (15.3) 0.54 (0.14–2.1)
Breastfed more than 12 months 53 (18.6) 66 (23.1) 0.92 (0.49–1.7) 34 (16.9) 39 (19.4) 1.4 (0.61–3.3) 19 (22.6) 27 (31.8) 0.22 (0.06–0.83)
Oral contraceptive use
   Never 68 (23.9) 42 (14.7) 1.0 55 (27.4) 37 (18.4) 1.0 13 (15.5) 5 (5.9) 1.0
   Ever 217 (76.1) 244 (85.3) 0.43 (0.26–0.72) 146 (72.6) 164 (81.6) 0.41 (0.22–0.75) 71 (84.5) 80 (94.1) 0.15 (0.03–0.65)
Hormone replacement therapy (HRT)
   None 129 (45.3) 126 (44.1) 1.0 58 (28.9) 60 (29.9) 1.0 71 (84.5) 66 (77.6) 1.0
   Combination therapy 101 (35.4) 103 (36.0) 0.93 (0.55–1.6) 96 (47.8) 94 (46.8) 0.99 (0.54–1.8) 5 (6.0) 9 (10.6) 0.47 (0.08–2.7)
   Other HRTc 55 (19.3) 57 (19.9) 0.96 (0.55–1.7) 47 (23.4) 47 (23.4) 1.1 (0.54–2.1) 8 (9.5) 10 (11.8) 0.75 (0.17–3.4)
Highest body mass index (BMI) after age 21 daysd
   BMI < 25 184 (64.6) 141 (49.3) 1.0 124 (61.7) 89 (44.3) 1.0 60 (71.4) 52 (61.2) 1.0
   25 ≤ BMI < 30 66 (23.2) 84 (29.4) 0.53 (0.34–0.84) 49 (24.4) 62 (30.8) 0.47 (0.27–0.83) 17 (20.2) 22 (25.9) 0.52 (0.19–1.4)
   BMI ≥ 30 35 (12.3) 61 (21.3) 0.38 (0.22–0.66) 28 (13.9) 50 (24.9) 0.29 (0.15–0.57) 7 (8.3) 11 (12.9) 0.30 (0.08–1.2)
P for trende    0.0003    0.0008    0.05
Number of mammograms, 1990–94
   Less than four 98 (34.4) 145 (50.7) 1.0 36 (17.9) 73 (36.3) 1.0 62 (73.8) 72 (84.7) 1.0
   Four or more 187 (65.6) 141 (49.3) 2.5 (1.6–4.0) 165 (82.1) 128 (63.7) 2.6 (1.5–4.6) 22 (26.2) 13 (15.3) 2.1 (0.67–6.4)
Socioeconomic status
Socioeconomic status before age 21
   Poor/working class 49 (17.2) 58 (20.3) 1.0 34 (16.9) 51 (25.4) 1.0 15 (17.9) 7 (8.2) 1.0
   Lower middle class 44 (15.4) 31 (10.8) 1.7 (0.86–3.5) 31 (15.4) 26 (12.9) 1.9 (0.84–4.5) 13 (15.5) 5 (5.9) 1.2 (0.16–8.6)
   Middle class 113 (39.6) 132 (46.2) 1.0 (0.58–1.7) 81 (40.3) 85 (42.3) 1.5 (0.80–2.9) 32 (38.1) 47 (55.3) 0.30 (0.07–1.3)
   Upper middle/upper class 79 (27.7) 65 (22.7) 1.3 (0.73–2.4) 55 (27.4) 39 (19.4) 2.2 (1.0–4.6) 24 (28.6) 26 (30.6) 0.23 (0.05–1.1)
Separating upper middle and upper versus poor/working class a
Upper middle class 68 (23.9) 63 (22.0) 1.1 (0.57–2.0) 46 (22.9) 38 (18.9) 1.6 (0.73–3.4) 22 (26.2) 25 (29.4) 0.22 (0.05–1.1)
Upper class 11 (3.9) 2 (0.7) 9.7 (1.9–49.0) 9 (4.5) 1 (0.5) 31.5 (3.3–298.6) 2 (2.4) 1 (1.2) 1.6 (0.03–82.1)
Highest degree obtained
   High school (HS) 69 (24.2) 66 (23.1) 1.0 55 (27.4) 55 (27.4) 1.0 14 (16.7) 11 (12.9) 1.0
   Some college or other post-HS 59 (20.7) 66 (23.1) 0.83 (0.47–1.4) 37 (18.4) 47 (23.4) 0.63 (0.32–1.3) 22 (26.2) 19 (22.4) 1.2 (0.32–4.9)
   Bachelor's 105 (36.8) 103 (36.0) 0.99 (0.59–1.7) 71 (35.3) 64 (31.8) 1.1 (0.59–2.1) 34 (40.5) 39 (45.9) 0.73 (0.19–2.8)
   Graduate 52 (18.2) 51 (17.8) 0.93 (0.50–1.7) 38 (18.9) 35 (17.4) 0.89 (0.42–1.9) 14 (16.7) 16 (18.8) 0.80 (0.17–3.8)
Religion in which raised
   Protestant 128 (44.9) 111 (38.8) 1.0 100 (49.8) 84 (41.8) 1.0 28 (33.3) 27 (31.8) 1.0
   Catholic 104 (36.5) 114 (39.9) 0.72 (0.47–1.1) 70 (34.8) 78 (38.8) 0.68 (0.40–1.1) 34 (40.5) 36 (42.4) 0.53 (0.20–1.4)
   Jewish 23 (8.1) 18 (6.3) 1.2 (0.56–2.6) 16 (8.0) 11 (5.5) 1.6 (0.57–4.3) 7 (8.3) 7 (8.2) 0.95 (0.18–4.9)
   Other 18 (6.3) 18 (6.3) 0.94 (0.42–2.1) 7 (3.5) 14 (7.0) 0.33 (0.11–1.0) 11 (13.1) 4 (4.7) 3.2 (0.60–16.7)
   None 12 (4.2) 25 (8.7) 0.39 (0.17–0.91) 8 (4.0) 14 (7.0) 0.53 (0.18–1.6) 4 (4.8) 11 (12.9) 0.20 (0.03–1.1)
Alcohol and tobacco use
Age began drinking alcohol
   Before age 21 years 228 (80.0) 255 (89.2) 1.0 156 (77.6) 176 (87.6) 1.0 72 (85.7) 79 (92.9) 1.0
   After age 21 years 57 (20.0) 31 (10.8) 2.8 (1.6–5.0) 45 (22.4) 25 (12.4) 3.0 (1.5–5.9) 12 (14.3) 6 (7.1) 2.9 (0.60–14.2)
Average drinks after age 21f
   <1 drink per week 81 (28.4) 104 (36.4) 1.0 56 (27.9) 68 (33.8) 1.0 25 (29.8) 36 (42.4) 1.0
   ≥ 1 drinks per week, <2 per day 137 (48.1) 149 (52.1) 1.1 (0.72–1.8) 90 (44.8) 106 (52.7) 0.63 (0.36–1.1) 47 (56.0) 43 (50.6) 3.5 (1.2–10.1)
   ~2 drinks per day 52 (18.2) 27 (9.4) 2.3 (1.2–4.4) 42 (20.9) 22 (10.9) 1.5 (0.70–3.3) 10 (11.9) 5 (5.9) 3.6 (0.79–16.5)f
   ≥ 3 drinks per day 15 (5.3) 6 (2.1) 3.6 (1.2–11.5) 13 (6.5) 5 (2.5) 2.9 (0.80–10.9) 2 (2.4) 1 (1.2)  
P for trende    0.004    0.090    0.030
Lifetime pack-years of cigarette smoking
   None 117 (41.1) 130 (45.5) 1.0 74 (36.8) 87 (43.3) 1.0 43 (51.2) 43 (50.6) 1.0
   Duration ≤ 8.25 years 39 (13.7) 38 (13.3) 1.3 (0.70–2.2) 24 (11.9) 24 (11.9) 1.3 (0.61–2.9) 15 (17.9) 14 (16.5) 2.3 (0.72–7.4)
   > 8.25 years to ≤ 15 years duration 29 (10.2) 42 (14.7) 0.81 (0.44–1.5) 21 (10.4) 28 (13.9) 0.99 (0.45–2.2) 8 (9.5) 14 (16.5) 0.38 (0.11–1.3)
   >15 years to ≤ 28.5 years duration 36 (12.6) 37 (12.9) 1.1 (0.61–2.0) 22 (10.9) 26 (12.9) 1.0 (0.47–2.3) 14 (16.7) 11 (12.9) 1.1 (0.34–3.8)
   Duration > 28.5 years 64 (22.5) 39 (13.6) 2.4 (1.3–4.2) 60 (29.9) 36 (17.9) 3.1 (1.6–5.9) 4 (4.8) 3 (3.5) 2.0 (0.18–21.2)
P for trende    0.02    0.004    0.78
  1. CI, confidence interval; OR, odds ratio. Statistically significant results are shown in bold. aWomen with complete full interviews were included in the multivariate analyses. ORs adjusted for age and other variables in this table are presented in normal font. Variables in italics are alternative categorizations of selected variables and are adjusted for age and the other variables in the table. bIncludes surgical biopsy alone and surgical biopsy in addition to fine-needle aspiration. cTook either only estrogen (N = 92) or only progesterone (N = 12) compounds, or took them during different times (N = 6), or name of hormone unknown (N = 2). dExcludes weight during pregnancy, nursing, or first 6 months after pregnancy. e P for linear trend in categories given are adjusted for age and other variables in the table. fFor women under age 50, those drinking about two drinks per day and those drinking three or more drinks per day were combined.