Table 3

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

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

Ozmen et al. World Journal of Surgical Oncology 2009 7:37   doi:10.1186/1477-7819-7-37