Table 3 Association of factors with mammographic breast density using odds ratios (OR) and 95% confidence intervals (CI), among women in Karachi, Pakistan

Age (years)

 < 35

2.18

0.81, 5.85

12.00

4.04, 35.65

35–45

2.93

1.65, 4.92

9.91

4.71, 20.84

46–54

1.14

0.69, 1.87

3.29

1.58, 6.86

55 and above

Ref

Ref

Socioeconomic status

Upper

0.94

0.38, 2.32

0.73

0.24, 2.17

Middle

0.95

0.41, 2.22

1.00

0.37, 2.71

Lower

Ref

Ref

Parity

Nullipara

0.95

0.47, 1.93

2.79

1.32, 5.91

 < 3

1.63

1.05, 2.53

1.94

1.10, 3.41

 > 3

Ref

Ref

AFB* (years)

 < 20

0.42

0.18, 0.97

0.28

0.10, 0.76

20–29

0.79

0.38, 1.65

0.54

0.23, 1.22

 > 30

Ref

Ref

Breastfeeding duration

 < 12 months

1.13

0.65, 1.95

1.09

0.55, 2.16

 > 12 months

Ref

Ref

Age at menarche

 < 12yrs

0.61

0.30, 1.23

0.56

0.25, 1.29

12-13yrs

0.8

0.49, 1.31

0.65

0.37, 1.17

 > 14yrs

Ref

Ref

Menopause

Menopause

0.38

0.24, 0.59

0.21

0.13, 0.36

Premenopause

Ref

Ref

Age at menopause

 < 45

0.92

0.48, 1.78

2.02

0.82, 5.01

 > 45

Ref

Ref

History of benign

Yes

1.72

1.08, 2.73

2.99

1.76, 5.09

No

Ref

Ref

Breast cancer

Yes

1.71

0.77, 1.77

0.66

0.39, 1.13

No

Ref

Ref

BMI (kg/m²)*

0.94

0.90, 0.98

0.80

0.75, 0.86

Physical activity* (h/week)

Walking

0.99

0.89, 1.09

0.95

0.83, 1.09

Moderate exercise

1.02

0.98, 1.05

1.00

0.96, 1.05

Vigorous exercise

Ref

Ref

Vitamin D (ng/ml)

 < 20

1.02

0.59, 1.77

1.12

0.58, 2.14

20–30

1.39

0.68, 2.85

1.67

0.73, 3.82

 > 30

1 (Ref)

1 (Ref)