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Table 3 Risk factors associated with increased or decreased risk of breast cancer.

From: Breast cancer risk factors in Turkish women – a University Hospital based nested case control study

Factors associated with increased breast cancer risk: women in the control group
(n = 2167) (%)
patients with breast cancer
(n = 1492) (%)
OR (95%CI) P value
Age (≥ 50) years 34.0 58.8 2.78 (2.42–3.18) < 0.001
Induced abortion 42.9 49.7 1.31 (1.13–1.53) < 0.001
Body mass index ≥ 25 55.2 64.2 1.46 (1.27–1.68) < 0.001
Family history of breast cancer (first degree relative) 5.0 7.2 1.46 (1.11–1.92) 0.008
Age at first birth (≥ 35 years) 0.9 2.6 3.06 (1.62–5.77) < 0.001
Factors associated with decreased breast cancer risk:     
Education (≥ 13 years) 48.8 40.3 0.71 (0.62–0.81) < 0.001
Spontaneous abortion 28.9 22.5 0.71 (0.60–0.85) < 0.001
Smoking 29.9 23.5 0.72 (0.61–0.85) < 0.001
Breast feeding 98.4 91.5 0.17 (0.11–0.27) < 0.001
Oral contraceptive use 27.8 18.4 0.59 (0.50–0.69) < 0.001
Nullipara 20.8 16.2 0.95 (0.92–0.98) < 0.001
Hormone replacement therapy 10.8 4.1 0.35 (0.26–0.47) < 0.001